CN102437317A - AB4.7 Hyperentropy Change Method for Non-stoichiometric Hydrogen Storage Alloys - Google Patents

Abstract

The invention provides a method for super-entropy change of AB _4.7 non-stoichiometric ratio hydrogen storage alloy, especially a hydrogen storage alloy based on MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 , and metal lithium as a super-entropy change reagent added again. The heterogeneous diffusion synthesis of hydrogen storage alloy battery anode materials with super-entropy change characteristics and the method of super-entropy change in alkaline batteries. The AB _4.7 non-stoichiometric ratio hydrogen storage alloy obtained by the present invention significantly improves the low-temperature discharge capacity. Compared with the usual industrial AB ₅ type hydrogen storage alloy, the low-temperature discharge capacity at minus -36°C or -30°C is increased to More than 3 times; Significantly improved the low-temperature discharge voltage of hydrogen storage alloy powder: Compared with the usual industrial AB ₅ type hydrogen storage alloy, the low-temperature discharge voltage increased by about 280mV on average at minus -36°C; solved the problem of MH-Ni battery or The technical problem that the low-temperature discharge power of the battery pack is difficult to meet the standard.

Description

AB4.7 Hyperentropy Change Method for Non-stoichiometric Hydrogen Storage Alloys

technical field

The invention relates to a super-entropy change method of AB _4.7 non-stoichiometric ratio hydrogen storage alloy. In particular, it involves the use of MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 as the base hydrogen storage alloy, and metal lithium as the super-entropy change reagent added again, through the heterogeneous diffusion of the two to synthesize a hydrogen storage alloy battery negative electrode with super-entropy change characteristics Materials and materials design methods for hyperentropy change in alkaline batteries.

Background technique

For a specified system, an increase in the degree of chaos is called an increase in entropy, and vice versa is a decrease in entropy. the

The hydrogen storage alloy plays the role of the negative electrode active material in the MH-Ni secondary battery. During the charging process, the hydrogen element in the electrolyte enters the hydrogen storage alloy to form a metal hydride, and the other part of the hydrogen element that does not form a metal hydride exists on the grain boundary. The entropy of the hydrogen storage alloy increases; on the contrary, during the discharge process, the hydrogen element in the hydrogen storage alloy returns to the electrolyte, and the entropy of the hydrogen storage alloy decreases; based on this, the charging and discharging process of the hydrogen storage alloy in the battery is an entropy change process. the

Add metal potassium to the hydrogen storage alloy that has been synthesized, and the process of adding metal potassium into the hydrogen storage alloy is obviously an entropy increase process; the hydrogen storage alloy with metal potassium is used for MH-Ni secondary batteries, The metal potassium on the surface of the hydrogen alloy powder encounters a high-concentration potassium hydroxide aqueous solution electrolyte, and the metal potassium reacts with the lye to form potassium hydroxide and enters the electrolyte. This process is an entropy reduction process for hydrogen storage alloys containing metal potassium. . Not only the metal potassium on the surface of the hydrogen storage alloy powder enters the electrolyte, but also the metal potassium inside the hydrogen storage alloy powder can enter the electrolyte at an appropriate time and under appropriate conditions as the charge and discharge cycle proceeds, resulting in a decrease in the entropy of the hydrogen storage alloy. This entropy reduction occurs simultaneously with the entropy reduction caused by the return of hydrogen in the hydrogen storage alloy to the electrolyte, and the addition of the two forms a greater change in entropy reduction. Compared with the reduction of entropy caused by the hydrogen element in the hydrogen storage alloy of the battery discharge (without adding metal potassium); the change of entropy is larger; use "super-entropy change" or "high-entropy change" change) definition is obviously more appropriate. The present invention adopts the former definition. the

The metal elements in the alkali metal group in the periodic table: lithium, potassium, sodium, rubidium and cesium, like the above-mentioned metal potassium elements added to hydrogen storage alloys, can all exhibit super-entropy change effects in batteries. These hydration elements (when encountering water, including the elements that react rapidly with water in the alkaline electrolyte in the battery) are very active, and they are used as super-entropy change external reagents, and the addition method and amount of addition to the hydrogen storage alloy , after the addition of positive and negative effects on battery performance, etc., it is obvious that careful design is required. The method used in this "careful design" is the "super-entropy change method". the

In other words: the method of hyperentropy change of hydrogen storage alloy is a design method with the object of hydrogen storage alloy and the special effect of entropy change of hydrogen storage alloy in the battery. This design method specifically includes: how to add super-entropy change reagents to hydrogen storage alloys, how to add them, and achieve good results after super-entropy changes in batteries, the method of mixing these metals and alloys, and hydrogen storage alloys as battery negative electrode alloy materials The design method of hydrogen storage alloy, etc., is the "super-entropy change method of hydrogen storage alloy" (method of super-entropy change on hydrogen storage alloy). the

In the alkaline earth metal group of the periodic table of elements: magnesium, calcium, strontium; in other main groups or subgroups: aluminum, zinc, tin, lead, cadmium, etc.; these metal elements encounter strong alkaline in alkaline batteries Aqueous electrolytes have a tendency and ability to react strongly and dissolve into aqueous electrolytes; they can all be used as candidate elements for hyperentropy change reagents added to hydrogen storage alloys. However, how to add and achieve the effect of super entropy change in the battery after adding also involves scientific and rational design methods. Even the selection of hyper-entropy-changing elements involves scientific rationality. For example, adding lead and cadmium as hyper-entropy-changing elements to hydrogen storage alloys is considered an unreasonable design method from the perspective of environmental protection, because the The use of hydrogen storage alloys in the anode alloy materials of MH-Ni secondary batteries violates the original intention of "MH-Ni batteries as green and ideal batteries in the 21st century". the

Another example: at the beginning of the industrialization of MH-Ni batteries, the hydrogen storage alloy powder used for the negative electrode active material of the battery has requirements for the raw material composition, especially the rare earth metal raw materials, which require low zinc and low magnesium. It is considered an unreasonable design method to add strong reaction elements to hydrogen storage alloys in alkaline batteries. The main reason is that the side reaction hydrogen will cause negative effects such as increased internal pressure of sealed batteries. This is disclosed in Chinese patent CN95121829.8 "Method for producing low-zinc and low-magnesium mixed rare earth metals" and Chinese patent CN95121833.6. This kind of low-zinc and low-magnesium mixed rare earth metals is called "battery grade mixed rare earth metals". With the in-depth research and application of La-Mg-Ni rare earth AB ₃ series hydrogen storage alloy powder, this "considered unreasonable design method" was abandoned by some research peers or companies.

In the process of rejecting the "irrationality" of hydrogen storage alloy powder, which is an ultra-entropy change element such as magnesium and zinc, used in the negative electrode active material of the battery, the representative view and practice are: "The hydrogen storage alloy contains zinc and other hyper-entropy change elements. Elements, used as anode alloy materials for MH-Ni secondary batteries, dissolve into the electrolyte during battery charging and discharging, and the hydrogen storage alloy itself will leave tiny pores due to its dissolution, and these micropores are often considered beneficial” . the

On October 6, 2010, the Chinese Patent Office published two invention patents filed by the American Bidirectional Battery Company in China entitled "Hydrogen Storage Alloys with High Porosity Surface Layer", and the publication numbers are CN101853937.A and CN101853938.A respectively. . The main "pore modifier" in this embodiment of the invention is metallic zinc, followed by metallic aluminum. If the invention is examined from the perspective of hyper-entropy change of the present invention, the invention can be interpreted as:

Zinc and aluminum can dissolve Zn(OH) ₂ and Al(OH) ₃ [Zn+2OH ^- → Zn(OH) ₂ ; Al+3OH ^- → Al(OH) ₃ ] in 6M-9M KOH strong alkali, The dissolution behavior of zinc metal in strong alkali is stronger than that of aluminum (the protective performance of the protective film is poor). After the dissolution of zinc and aluminum in the hydrogen storage alloy, vacancies or holes are left on the hydrogen storage alloy; at the same time, the dissolution of zinc and aluminum also has a super entropy change for the hydrogen storage alloy system.

According to the invention, zinc is used as a "pore modifier" to form a porous layer on the surface of the alloy powder, which is conducive to the catalytic reaction. The complex impedance measurement of the AC impedance method shows that at a low temperature of -30 ° C, the hydrogen storage alloy is used as the negative electrode active material of the battery. The specific power of the control blank is significantly increased, which contributes a lot to solving the low-temperature discharge performance of the battery. the

However, looking at the disadvantages of this invention from the perspective of the hyper-entropy change method of the present invention has:

As the main element of super-entropy change, zinc is not clearly stated how it is added to the hydrogen storage alloy, that is, the super-entropy change method that the super-entropy change element zinc increases the entropy of the hydrogen storage alloy is not clearly stated. It is well known in the industry that the boiling point of metallic zinc is 907°C. According to the invention, the smelting temperature is 1350°C and the casting temperature is 1280°C. These temperatures are far beyond the boiling point (gasification point) of metal zinc. Metal zinc must be gasified, and only a trace amount of zinc remains in the hydrogen storage alloy. In addition, zinc dissolves Zn(OH) ₂ in KOH strong alkali to form a gel, which has negative effects on battery self-discharge, that is, the super-entropy change system method that zinc reduces the entropy of hydrogen storage alloys is not clearly stated; these are intuitive shortcomings of the invention.

On September 29, 2010, the Chinese Patent Office disclosed the CN101849305.A invention patent applied by Japan's Yuasa Battery Company in China. The hydrogen storage alloy system of the invention is a magnesium-containing rare earth AB ₃ system, or called a rare earth-magnesium-nickel hydrogen storage alloy; the typical composition is La _17.9 Ca _0.7 Mg _4.7 Ni _76.7 . The super-entropy-changing elements in the inventive alloy are magnesium and calcium; magnesium and calcium can dissolve Mg _{( OH} ) and Ca(OH) in the KOH strong base of 6M-9M and enter the electrolyte [Mg+ ^2OH- →Mg( OH) ₂ ; Ca+2OH ^- →Ca(OH) ₂ ], resulting in a decrease in the entropy of the hydrogen storage alloy. This entropy reduction occurs simultaneously with the return of the hydrogen element in the hydrogen storage alloy to the electrolyte, resulting in a huge entropy reduction change, that is, a "super entropy change".

This invention has two obvious advantages: one, although metal magnesium (boiling point 1110 ℃) and calcium (boiling point 1240 ℃) also have the gasification problem similar to metal zinc in hydrogen storage alloy smelting and casting, but this invention is very useful as a super The problem of how to add magnesium, the main element of entropy change, into the hydrogen storage alloy is explicitly stated as the use of "melt spinning method". This enables magnesium and calcium to be improved in the systematic aspect of the entropy increasing method of the ultra-entropy hydrogen storage alloy. the

Second, magnesium and calcium are jointly designed as super-entropy-changing elements. In the process of battery discharge entropy reduction, calcium is more active than magnesium, and calcium assumes the role of "sacrificial anode", which controls the dissolution rate of magnesium in KOH strong alkali to form Mg(OH) ₂ to a certain extent; slows down hydrogen storage Structural collapse of the alloy due to magnesium dissolution.

The shortcoming of this invention is also the shortcoming of a large number of related inventions of the current magnesium-containing rare earth AB ₃ system, or the rare earth-magnesium-nickel hydrogen storage alloy system: the problem of structural collapse caused by the dissolution of magnesium in the electrolyte, in other words The problem that the super-entropy-changing element magnesium reduces the entropy of the hydrogen storage alloy and affects the cycle life cannot be completely solved.

On June 16, 2010, the Chinese Patent Office published the CN101740768.A invention patent applied by China BYD Company. The magnesium-containing rare earth AB ₃ hydrogen storage alloy of the embodiment of the invention also involves the combination design of hyper-entropy elements, that is, the combination of lithium and aluminum and the combination of tin and aluminum. Typical compositions are: La _0.95 Li _0.05 Ni _3.0 Co _0.2 Mn _0.2 Al _0.1 and La _0.65 V _0.05 Cr _0.3 Ni _3.0 Sn _0.2 Mn _0.2 Al _0.1 . The super-entropy-changing elements lithium, aluminum and tin in the alloy of the invention can undergo partial reactions in the 6M-9M KOH electrolyte: Li+ ^OH- →Li(OH); Al+ ^3OH- →Al(OH) ₃ ; Sn+ 4OH ^- →Sn(OH) ₄ ; the dissolution causes the entropy reduction of the hydrogen storage alloy. The shortcoming of this invention is that it does not mention any effect of entropy reduction on alloys and batteries; at the same time, it does not mention super-entropy elements with a melting point of 180.6°C and a boiling point of 1330°C—how lithium metal is added to the AB _3.5 and AB _3.8 and the invention is focused on the conventional "the range of the added amount of Al, Co and Mn". The binary combination of hyper-entropy-changing elements used in this invention does not constitute a limit to the creativity of the ternary combination of hyper-entropy-changing elements in the present invention.

On December 25, 2004, the Chinese Patent Office authorized the ZL02158001.4 patent entitled "Lithium-containing composite hydrogen storage alloy electrode material and its preparation method" applied by Professor Wu Feng of Nankai University in China. The advantages and disadvantages of this invention have:

The core element of the invention is lithium. The core technology is: adding metal lithium to hydrogen storage alloys such as AB ₅ type through MA technology (mechanical alloying technology), during which metal lithium acts as a super-entropy-changing element that "increases the entropy of the hydrogen storage alloy"; adding metal lithium The hydrogen storage alloy is used in the battery, in which lithium metal dissolves Li(OH) in the lye: Li+OH ^- → Li(OH), so that the hydrogen storage alloy produces micropores. In this process, metal lithium takes on the role of the super-entropy-changing element that "reduces the entropy of the hydrogen storage alloy"; the beneficial effect of this super-entropy-changing process is: "improves the catalytic activity of the negative electrode of the Ni/MH battery, and at the same time improves the cycle life of the battery. ". Apparently, this surface pore-making method using the super-entropy-changing element lithium as the "pore modifier" is better than the CN101853937.A and CN101853938.A disclosed by the American Bidirectional Battery Company in the Chinese Patent Office in the following six years. The method of "modifier" has greatly improved the degradation of conventional battery electrolytes by the dissolution of hyper-entropy-changing elements.

However, the disadvantage of this invention is that the particle size of the hydrogen storage alloy powder is moderate and strong in the manufacturing process of the slurry negative electrode or dry negative electrode. granularity requirements. the

The Chinese patent patent No. ZL92100029.4 of "active material of hydrogen storage alloy electrode" applied by Nankai University in Tianjin, China, its super-entropy-changing element is still lithium; the super-entropy-changing element lithium that is responsible for "increasing the entropy of hydrogen storage alloy" is based on Lithium-containing master alloy is added to ensure the stability of the added components in the hydrogen storage alloy; and for the super-entropy-changing element lithium that "reduces the entropy of the hydrogen storage alloy", its beneficial effect of entropy reduction in the battery is explained as : Li+OH ^- → Li(OH) increases the concentration of Li(OH) in the battery electrolyte and protects the positive electrode; The interior of the hydrogen alloy structure is not oxidized". The disadvantage of this invention is: the details of "the super-entropy-changing element lithium is added in the form of lithium-containing master alloy" are not clearly stated, which leads to the lack of social benefits of the patent. In addition, the interaction between Al and Li hyperentropy changing elements and the simple design principle of the interaction between Al, Zn and Li three hyperentropy changing elements and the quantitative relationship of Al, Zn and Li in this embodiment are not clearly shown.

On December 15, 2010, the Chinese Patent Office published the CN101914699A invention patent entitled "Molten Salt Electrosynthesis Method Adding Magnesium, Lithium, Sodium and Potassium to Hydrogen Storage Alloy". The advantage of this invention is that four hyper-entropy-changing elements of magnesium, lithium, sodium and potassium can be safely and effectively added to the hydrogen storage alloy through the same molten salt electrolytic cell in the form of electroosmosis and electrolysis interaction. The disadvantage is that this method of addition The requirements for technical proficiency and the necessary equipment for molten salt electrosynthesis are relatively high, and it is slightly insufficient in terms of practicability such as simple process and small equipment investment. the

In recent years, the concept of high-entropy alloys in the field of structural materials has been gradually recognized by personnel in the field of functional materials (Materials Herald, Research Progress in Multivariate High-Entropy Alloys, Volume 20, Issue 4, 2006, P4-14); even the Chinese Patent Office has published High-entropy materials such as brazing material (CN101590574, CN101554686 and CN101554685), wear-resistant materials (CN101386928), magnetic materials (CN101307465), composite materials (CN101215663 and CN1827817), and catalyst alloy materials (CN101214443 and CN101195091) (High-entropy alloys) patent. However, in the field of hydrogen storage alloys, based on the "high-ratio entropy change" (high-ratio entropy change), or more strictly called "super-entropy change" (super-entropy change) to study the hydrogen storage alloy and the alloy entropy change in The battery is still blank in use. the

In summary: In the existing patented technologies including the above-mentioned published patents, as well as published research papers, the entropy change process of the hydrogen element entering and leaving the hydrogen storage alloy in the battery charging and discharging process is ignored. The existence of the scientific essence; the existence of the scientific essence of the addition and dissolution of the hydrogen storage alloy in the alkaline electrolyte to form a greater entropy change—super entropy change; thus causing the hydrogen storage alloy to dissolve the element in the alkaline electrolyte The design is messy and lacks theoretical support. The design of hydrogen storage alloys for MH-Ni batteries based on the super-entropy change design method, especially the super-entropy change design method based on the interaction of metal lithium, tin and aluminum ternary super-entropy change elements in the AB _4.7 system has not been seen Patent publication and article coverage.

Contents of the invention

In order to solve the problems existing in the prior art, the object of the present invention is to provide the method for the hyperentropy change of the AB _4.7 non-stoichiometric ratio hydrogen storage alloy, especially to provide a hydrogen storage alloy with MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 as the matrix, to Lithium metal is the super-entropy change reagent added again, and a hydrogen storage alloy battery negative electrode material with super-entropy change properties is synthesized through heterogeneous diffusion of the two, and a method for using it as a material for super-entropy change in an alkaline battery.

The method for the hyperentropy change of the hydrogen storage alloy is based on the hydrogen storage alloy, and is a method aimed at producing special effects in the battery by the entropy change of the hydrogen storage alloy. This method specifically includes: how to add the super-entropy change agent to the hydrogen storage alloy, and the amount of addition and achieve good results after the super-entropy change in the battery, the method of mixing these metals and alloys, and the hydrogen storage alloy as the negative electrode alloy material of the battery. The design method, etc., is the "super-entropy change method of hydrogen storage alloy" (method of super-entropy change on hydrogen storage alloy). the

The design principle of the super entropy change method of the AB _4.7 non-stoichiometric hydrogen storage alloy of the present invention:

(1) The design of the super-entropy-changing element metal aluminum:

One of the purposes of adding the super-entropy-changing element metal aluminum in the present invention is: when the Al on the surface of the MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 hydrogen storage alloy particles reacts with the concentrated potassium hydroxide solution as the battery electrolyte, the MmNi _4.3 Al _0.3 Fe _0.05 The surface of Sn _0.05 hydrogen storage alloy particles forms a "nickel-rich porous structure", and the activation energy of the battery charge and discharge reaction (H ⁺ +e←→H) is reduced; the low temperature charge and discharge performance of the battery is improved.

The principle of determining the amount of super-entropy-changing element metal aluminum is: in the MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 hydrogen storage alloy system, the ratio of 0.3 mole fraction of Al to 4.3 mole fraction of Ni is about 1:14; The weight ratio is about 1:31; the determination of this ratio mainly balances and optimizes the relationship between the formation of "nickel-rich porous structure" on the surface of the hydrogen storage alloy particles and the "structure collapse caused by the release of Al" inside the hydrogen storage alloy particles. When the amount of aluminum added is large, the pore density of the "nickel-rich porous structure" formed on the surface of the hydrogen storage alloy particles increases, and the number and structure of the "nickel-rich porous structure" tend to approach the number of pores of "Raney Nickel" And structure; However, the negative effect of "Raney nickel" pore quantity and structure to the present invention is: because " go out too much Al, cause the CaCu ₅ structure collapse of reversible hydrogen storage ". The hydrogen storage alloy of the present invention utilizes the Raney nickel principle and maintains a large difference in the design principle in quantity, which is embodied in:

It is well known to industrial catalysis colleagues that Raney Nickel, a solid-state heterogeneous hydrogenation catalyst with a history of nearly 90 years of widespread use, uses a pore-forming method of treating nickel-aluminum alloys with concentrated sodium hydroxide solution to dissolve the aluminum. That is, Al in nickel-aluminum alloy undergoes 2Al+2NaOH+6H ₂ O→2Na[Al(OH) ₄ ]+3H ₂ , leaving nickel with many micropores of different sizes, which can strongly absorb hydrogen and become Reaction center for catalytic hydrogenation. The weight ratio of Al and Ni nickel in Raney nickel is about 1: 5 (USP 1,628,190, 1927) or 1: 1; The present invention adopts the weight ratio of Al and Ni nickel of 1: 31, and this is far less than Raney nickel The adoption of the weight ratio of Al to Ni nickel is based on the main principle of the design: borrowing the principle of Raney nickel to make holes, while avoiding too much aluminum in Raney nickel, resulting in a large number of holes and the resulting The structure collapsed".

The design method of adding the super-entropy-changing element metal aluminum to the alloy, that is, the design principle that metal aluminum increases the entropy of the hydrogen storage alloy is: since the boiling point of metal aluminum Al is about 1800 ° C, the melting temperature of hydrogen storage alloy induction melting is usually 1380 ° C Between ℃ and 1600℃, it can be induction smelted together with rare earth metal Mm, metal nickel Ni, metal iron Fe and metal tin Sn. the

In a word, the design of metal aluminum in the present invention is to comprehensively consider the influence of both positive and negative factors of entropy increase and entropy decrease caused by metal aluminum on hydrogen storage alloys, especially pay attention to the negative effects of excessive metal aluminum—because of " Excessive removal of Al will cause the collapse of the CaCu ₅ structure for reversible hydrogen storage", while the Raney nickel design pursues a porous catalytic surface, which has nothing to do with the CaCu ₅ structure for reversible hydrogen storage, so even if there is too much Al, the Raney nickel will cause the largest reduction in entropy Transformation is what it needs.

(2), the design of the super-entropy-changing element metal tin:

The purpose of adding the super-entropy-changing element metal tin of the present invention is similar to that of the above-mentioned super-entropy-changing element metal aluminum; the principle of determining the amount of addition is also similar; the design principle of increasing the entropy of the hydrogen storage alloy is also similar; the difference is:

The amount of added metal Al accounts for about 2wt% of the weight percentage of the MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 matrix hydrogen storage alloy; while the amount of metal Sn accounts for about 1.5wt%; the amount of added metal Sn is less than the amount of metal Al The design principle is:

①For Ni-Sn binary alloys, when the amount of metal Sn is greater than 3wt% in Ni-Sn binary alloys, the proportion of Ni ₃ Sn intermetallic compounds formed increases linearly, and the Ni ₃ Sn intermetallic compounds have the ability to reduce the discharge capacity of hydrogen storage alloys negative effect; this is one of the reasons why the amount of metal Sn designed by the present invention accounts for about 1.5wt% in the MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 hydrogen storage alloy system;

②Although the boiling point of metal Sn is 2270 °C, its melting point is about 232 °C, such a low melting point, in the subsequent solid-liquid or solid-gas heterogeneous diffusion process of lithium addition; metal Sn is easy to thermally segregate to MmNi The _{surface of 4.3 Al 0.3 Fe 0.05 Sn 0.05 hydrogen} storage alloy particles is often referred _to as the _phenomenon of "running tin". Accounting for 1.5wt% is one of the other reasons.

(3), the design of the super-entropy-changing element lithium metal:

①Using solid-liquid diffusion reaction to increase the entropy of the matrix hydrogen storage alloy:

Metal lithium is the element with the smallest atomic radius among metal atoms. Its melting point is about 181°C and its boiling point is about 1370°C. The small atomic radius makes it have a strong diffusion ability in another metal or alloy. the

Metal lithium and hydrogen storage alloy are mixed together. In a closed oxygen-free environment, when the temperature rises above the melting point of metal lithium (181°C), metal lithium will melt into a liquid state. If it does not exceed the melting point of hydrogen storage alloy (1300°C- 1350°C), the hydrogen storage alloy is still solid; the liquid metal lithium diffuses into the solid hydrogen storage alloy, that is, the usual solid-liquid diffusion reaction occurs. The result of this solid-liquid diffusion reaction is that liquid metal lithium atoms infiltrate into the solid hydrogen storage alloy, which is also commonly known as "lithium penetration" in the industry. the

When the immobilized hydrogen storage alloy is the research system, the metal lithium in this solid-liquid diffusion reaction acts as a super-entropy change agent, and the hydrogen storage alloy as the research object is also often called in this process: the "metal lithium" Obviously, the "lithiation" process is essentially a process in which the entropy of the matrix hydrogen storage alloy increases. the

② Effect of solid-liquid diffusion reaction conditions on entropy reduction of matrix hydrogen storage alloy:

The relative quantity, reaction temperature and reaction time of the two reactants of the solid-liquid diffusion reaction—the metal lithium ribbon and the hydrogen storage alloy powder—have a great influence on the product of the solid-liquid diffusion reaction, in other words, it has a significant influence on the effect of "lithium penetration". This effect is mainly manifested in the impact on room temperature discharge specific capacity, low temperature discharge performance, charging, activation performance, median voltage and the entire discharge V-t curve. the

Too much or too little addition of metal lithium to the matrix hydrogen storage alloy will reduce the discharge specific capacity at room temperature. The visual result of this effect is shown in Figure 7. It can be seen from Figure 7 that the appropriate ratio of metal lithium to the matrix hydrogen storage alloy It is very important to ensure and improve the discharge specific capacity at room temperature. The ideal discharge specific capacity at room temperature can be achieved when the amount of metal lithium added to the matrix hydrogen storage alloy is about 0.5wt% or 4wt%. The main reasons are:

When metal lithium encounters hydrogen, lithium hydride (LiH) can be generated, that is, Li+H→LiH; during the entropy reduction process of LiH, the dissociation of LiH (LiH→Li+H) is the basis of discharge, which penetrates into the matrix storage The amount of metal lithium in the deep layer of the hydrogen alloy is too large, and the amount of lithium hydride formed is large, and congestion will occur during the diffusion process of dissociated H. This diffusion channel is not smooth, resulting in a decrease in the discharge specific capacity at room temperature. If the amount of metal lithium in the layer is too small, the role of LiH as a "hydrogen source" will be weakened, and the discharge specific capacity at room temperature will also decrease due to the formation of too little lithium hydride. the

Similar to this, Figures 1, 3, 6, 2 and 4 and 5 respectively show the effects of different amounts of added lithium on low-temperature discharge performance, charging, activation performance, median voltage and the entire discharge V-t curve. the

The super entropy change method of AB _4.7 non-stoichiometric hydrogen storage alloy of the present invention, its steps are as follows:

1) The preparation method of matrix hydrogen storage alloy MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 is as follows:

According to the ratio of MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 chemical formula for material selection and batching, wherein, Mm is mixed rare earth metal ingot, Ni is metal nickel plate, Al is metal aluminum block, Fe is metal iron rod and Sn is metal tin plate, the purity of all metals is 99.95wt%; the composition and proportion of mixed rare earth metals are: 61wt% for La, 20wt% for Ce, 15wt% for Nd, and 4wt% for Pr; In the induction melting furnace crucible, the mixed rare earth metal ingots and iron rods placed in the induction melting furnace crucible are used to remove the oxide skin; the induction melting furnace is vacuumed to a vacuum of 10 ^-2 Pa and then filled with argon Gas is used as a protective atmosphere, increase the electric power until all the metal charges are melted and start timing, smelt for 20 minutes, keep the melting temperature at 1450°C±50°C, then cast and take out the furnace to obtain a hydrogen storage alloy with a matrix of MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 ; During the preparation of hydrogen storage alloys, super-entropy-changing elements metal Al and metal Sn are added by induction melting;

2) Lithium metal is an ultra-entropy change reagent, and the method of "lithiation" MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 matrix hydrogen storage alloy is as follows:

(1) The obtained MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 matrix hydrogen storage alloy ingot is pulverized into powder by jet milling, and passed through a 300-mesh sieve;

(2) According to the weight ratio of the hydrogen storage alloy powder and the metal lithium strip is 100 g: 0.5 g, put the metal lithium strip on the bottom of the crucible, sprinkle the matrix hydrogen storage alloy on it, cover the crucible lid, and put it in the resistor In the furnace, the mechanical pump was evacuated to the order of 10 ^-2 Pa and then filled with argon as a protective atmosphere; the electric furnace started to heat up, and the temperature system for heating up and keeping warm was determined as follows: take 1.5 hours to raise the temperature to 542°C and use this as the time Timing at the starting point, keeping the temperature for 20 hours, then using 3 hours to raise the temperature to 903°C, and holding it at 903°C for 0.5 hours, then cooling to room temperature and taking it out of the furnace to obtain lithiated MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 storage Hydrogen alloy powder agglomerates; or,

(the hydrogen storage alloy powder described in 3 and metal lithium belt weight ratio are 100 grams: 1 gram; All the other are the same as (1);

(4) According to the weight of hydrogen storage alloy powder 100 grams to 2 grams of metal lithium strip, put the metal lithium strip on the bottom of the crucible, sprinkle the base hydrogen storage alloy on it, cover the crucible lid, and put it in the resistance furnace , the mechanical pump was evacuated to the order of 10 ^-2 Pa, and then filled with argon as a protective atmosphere; the electric furnace started to heat up, and the temperature system for heating up and keeping warm was determined as follows: take 1.2 hours to heat up to 260°C and use this as the starting point of the time Timing and heat preservation for 18 hours, then raising the temperature to 813°C for 3 hours, and holding at 813°C for 1 hour, then cooling to room temperature and taking out the furnace; obtained lithiated MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 hydrogen storage alloy powder Agglomerates; super-entropy-changing element metal Li is added by heterogeneous reaction;

(5) The weight ratio of the hydrogen storage alloy powder and metal lithium strip is 100 grams: 3 grams or 100 grams: 5 grams; the rest are the same as (4);

3), the preparation method of MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 hydrogen storage alloy powder aggregates for MH-Ni battery negative plate after lithiation:

Pound the obtained lithiated MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 hydrogen storage alloy powder aggregates into powder blocks, and add 10 grams of carboxymethyl cellulose (CMC) aqueous solution with a concentration of 2 wt% according to 100 grams of hydrogen storage alloy powder blocks , a concentration of 8 grams of polyvinyl alcohol (PVA) aqueous solution of 0.8wt% and a concentration of 7 grams of crosslinked polyacrylic acid sodium (PAANa) aqueous solution of 1wt%, with the described alloy powder block and three kinds as bonding Pour the CMC, PVA, PAANa aqueous solution of the agent into the mixer and stir for 2 hours, let it stand for 2 hours, and then transfer it to the hopper of the battery plate pulling machine. The nickel-plated punching steel strip is used as the current collector, and the battery plate The pulping machine performs mechanical pulping, rolling, and drying to obtain the negative plate of the battery;

4), the design method of the negative plate of the battery in the MH-Ni simulation battery once again undergoes hyperentropy change reaction:

(1), the battery negative plate that step (3) is obtained is cut, removes burr, is used for assembling 100 ampere hours square analog batteries after its area specific capacity is measured electrochemically;

(2), the positive plate of the 100 ampere-hour square analog battery selects commercially available sintered nickel anodes, and fixes the quantity of sintered nickel anode plates according to the given area specific capacity of commercially available sintered nickel anodes and makes the quantity just satisfy 100 amperes hour;

(3) The negative plate of the battery is designed according to the total capacity of 170 ampere hours, and then the area of the negative plate of the battery should be cut according to the measured electrochemical area specific capacity value to meet the ratio of the number of negative plates to the sintered nickel anode plate The number of plates is 1 more;

(4) Choose polypropylene non-woven fabric battery separator; repeat the stacking order of a sintered nickel anode plate, a layer of polypropylene non-woven battery separator and then a negative electrode plate, all positive 1. After the negative plates are stacked, respectively weld the tabs of the positive plate and the tabs of the negative plate together, and at the same time weld an electrode lead-out wire on the welded positive and negative tabs to form a square battery core;

(5) Put the battery core in the stainless steel battery case; take the sum of the design capacity of the positive and negative electrodes as the base number, that is, 270 ampere-hours as the base number, and obtain the weight value according to the product of the base number and the 1.88 ampere-hours/gram coefficient Inject the KOH aqueous solution with a concentration of 31wt% into the stainless steel battery case with the battery core and seal the battery case;

(6) Charge the simulated battery with a current of 10 amps for 13.5 hours, and then put it in an oven at a constant temperature of 50°C±1°C for 96 hours. The non-stoichiometric ratio of AB _4.7 in the battery is The super entropy change reaction before the hydrogen alloy battery is formed is all completed.

5) Electrochemical characterization method of hydrogen storage alloy with super-entropy change characteristics as battery negative electrode alloy material:

After lithiation, the hydrogen storage alloy powder is ground into a 300-mesh alloy powder, and the alloy powder is used as the negative electrode active material; it is mixed with carbonyl Ni powder at a mass ratio of 1:6, and isostatically pressed into a Φ13mm sheet as the battery negative electrode. Sintered NiOOH/Ni(OH)2 is used as the positive electrode, and the capacity of the positive electrode is 5 times larger than that of the negative electrode; the positive and negative electrodes are separated by a nylon diaphragm, soaked in 7.5M KOH solution to form a negative-limited simulated battery, in which the electrolyte is added by weight It is 25 times the weight of the added hydrogen storage alloy powder; the battery performance is tested with a DC-5 battery tester, and the computer connected to it collects and processes data for the host computer. The ultra-low temperature refrigerator and constant temperature water bath are used for low temperature and high temperature tests respectively. The method for measuring the discharge performance of the high-temperature simulated battery is as follows: Based on the weight of the hydrogen storage alloy powder added to the simulated battery, charge the simulated battery for 5 hours at a room temperature of 60mA/g, put it in a refrigerator or a constant temperature water bath, and charge the simulated battery at a given high, Low temperature setting; freezing or warming in low or high temperature environment for 8 hours, followed by discharge operation. The battery is essentially a "negative limit MH-Ni simulation experimental battery for the determination of negative active materials."

6), 100 Ah square analog battery low temperature test method:

Use the ZM2030 battery charging and discharging instrument to charge the simulated battery with a current of 20A for 5.5 hours at room temperature, then put it in the refrigerator, and set it according to the given low temperature; freeze it in a low temperature environment for 8 hours, and then charge it with a current of 20A The current discharges the simulated battery. the

Beneficial effects: 1), significantly improved the low-temperature discharge capacity of the hydrogen storage alloy powder: the AB _4.7 non-stoichiometric ratio hydrogen storage alloy obtained by the super-entropy change method of the present invention, compared with the usual industrial AB ₅ type hydrogen storage alloy, At minus -36°C or -30°C, the low-temperature discharge capacity is increased to more than three times; this is specifically disclosed in Figure 1. It can be seen from Figure 1 that under the synergistic action of lithium, aluminum and tin, the maximum discharge specific capacity at -36°C and -30°C respectively reaches 162mAh/g and 221mAh/g; while the usual industrial AB ₅ type The hydrogen storage alloy is less than 30mAh/g and 70mAh/g at this temperature. At present, most MH-Ni batteries discharge little or almost no electricity at a low temperature of -35°C or -30°C. One of the main reasons is the limitation of the hydrogen storage alloy powder as the negative electrode active material. The hydrogen storage alloy powder of the present invention The improvement of low-temperature discharge capacity has broken through the core technical barriers of MH-Ni battery low-temperature discharge.

2), significantly improved the low-temperature discharge voltage of the hydrogen storage alloy powder: the AB _4.7 non-stoichiometric ratio hydrogen storage alloy obtained by the ultra-entropy change method of the present invention, compared with the usual industrial AB ₅ type hydrogen storage alloy, has a temperature of - At 36°C, the low-temperature discharge voltage increases by an average of about 280mV; as shown in Figure 2, it is visually revealed, and it is specifically revealed in the Vt curves of Figure 4 and Figure 5,

It can be seen from Figure 2 that under the synergistic effect of the two hyper-entropy-changing elements, aluminum and tin, the median value of the discharge voltage relative to the sintered nickel anode at minus -36°C reaches about 1250 millivolts (mV). Under the synergistic action of the three hyper-entropy-changing elements, lithium, aluminum and tin, the average value of the median discharge voltage at -36°C reaches about 1280 millivolts; while the median discharge voltage of the usual industrial AB ₅ hydrogen storage alloys at this temperature is Fluctuates around 1000 millivolts.

At present, the power of most MH-Ni batteries and battery packs is not up to the standard at a low temperature of -35°C. One of the main reasons is that the industrial AB ₅ hydrogen storage alloy powder used as the negative electrode active material has a plateau voltage of 1200mV or slightly higher at room temperature. And when the temperature drops to -35°C below zero, the platform voltage of the discharge voltage drops to 1000mV; when the temperature drops to -40°C below zero, the platform voltage of the discharge voltage drops to the range of 950mV-980mV. It is well known in the industry that the output power of a battery or battery pack is the product of the output voltage and the output current; it can be seen that the AB _4.7 non-stoichiometric ratio hydrogen storage alloy low-temperature discharge voltage obtained by the super-entropy change method of the present invention has solved the problem of MH- The technical problem that the low-temperature discharge power of Ni battery or battery pack is not up to standard.

3), the regular results of the AB _4.7 non-stoichiometric ratio hydrogen storage alloy charge retention ability obtained by the super entropy change method of the present invention provide important parameters for the design of low self-discharge batteries:

The charge retention ability of hydrogen storage alloy powder, referred to as the "charge" performance of hydrogen storage alloy powder, is one of the main factors affecting the self-discharge performance of batteries. In the AB _4.7 non-stoichiometric hydrogen storage alloy obtained by the super-entropy change method of the present invention, during the synergistic action of the three super-entropy-changing elements lithium, aluminum and tin, when the third super-entropy-changing element—lithium is added Falling in the range of 1wt%-4wt%, the charging performance of the hydrogen storage alloy is significantly increased. This has intuitive and concrete disclosure in accompanying drawing 3 of the present invention. This rule provides important inspiration for balancing the relationship between "LiOH concentration in the electrolyte - positive electrode active material configuration change - negative electrode surface pore formation", and also provides a new technical path for obtaining low self-discharge batteries.

Description of drawings

Figure 1 shows the discharge of the hydrogen storage alloy powder of the present invention with "the synergistic effect of two hyper-entropy-changing elements of aluminum and tin" and "the synergistic effect of three hyper-entropy-changing elements of lithium, aluminum and tin" at a low temperature of -22°C--36°C The representative change chart of specific capacity. In Figure 1: Curve 1 is the low-temperature discharge curve of the simulated battery negatively limited by the MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 hydrogen storage alloy under the synergistic effect of two hyperentropy-changing elements, aluminum and tin; Curves 2, 3 and 4 are lithium, aluminum Low-temperature discharge control curves of MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 -Li _(X) hydrogen storage alloys synergistically acting with three hyperentropy-changing elements of tin in a negatively limited simulated battery; the lithiation equivalents of curves 2, 3 and 4 Respectively corresponding to: "100 grams of hydrogen storage alloy powder to add 2 grams, 1 gram and 0.5 ratio of metal lithium strip".

Fig. 2 is the "synergy of two hyper-entropy-changing elements of aluminum and tin--MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 " and "the synergy of three hyper-entropy-changing elements of lithium, aluminum and tin--MmNi _4.3 Al _0.3 A representative diagram of the change of the median value of the discharge voltage of Fe _0.05 Sn _0.05 -Li _(X) ” hydrogen storage alloy powder at a low temperature of -36°C as the lithiation equivalent increases. It can be seen from Figure 2 that the addition of metal lithium can significantly increase the median discharge voltage of MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 .

Fig. 3 is the "synergy of two hyper-entropy-changing elements of aluminum and tin--MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 " and "the synergy of three hyper-entropy-changing elements of lithium, aluminum and tin--MmNi _4.3 Al _0.3 A representative diagram of the chargeability of Fe _0.05 Sn _0.05 -Li _(X) ” hydrogen storage alloy powder at room temperature as the lithiation equivalent increases. It can be seen from Figure 3 that the addition of metal lithium can significantly increase the charge retention capacity of MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 . Among them, the lithiation equivalent of "100 grams of hydrogen storage alloy powder added to the ratio of 3 grams of metal lithium ribbon" corresponds to the MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 -Li _(X) " hydrogen storage alloy powder with the highest relative improvement in charging performance.

Fig. 4 is the simulated negative confinement of the hydrogen storage alloy powder of "the synergistic effect of three hyper-entropy elements of lithium, aluminum and tin - MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 -Li _(X) " at a low temperature of -36°C The Vt curve of discharge in the battery (Vt curve refers to: discharge voltage (V) - discharge time (t) change curve).

Curve 1, curve 2 _, curve 3 and curve 4 in Fig. 4 correspond to 0.5wt%, _1wt %, _5wt % and _3wt % of lithiation equivalent respectively; 0.5 gram, 1 gram, 5 gram and 3 gram metal lithium strip ratio" equivalent amount.

Fig. 5 is the "synergy of two hyper-entropy-changing elements of aluminum and tin--MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 " and "the synergy of three hyper-entropy-changing elements of lithium, aluminum and tin--MmNi _4.3 Al _0.3 Vt curves of Fe _0.05 Sn _0.05 -Li _(X) ” hydrogen storage alloy powder discharged in a simulated negative-limited battery at a low temperature of -36°C. Curve 1 in Figure 5 is the Vt curve of MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 ; Curve 2 and Curve 3 correspond to the Vt curves of 2wt% and 4wt% lithiated equivalents, respectively.

Fig. 6 is the "synergy of two hyper-entropy-changing elements of aluminum and tin--MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 " and "the synergy of three hyper-entropy-changing elements of lithium, aluminum and tin--MmNi _4.3 Al _0.3 Activation curve of Fe _0.05 Sn _0.05 -Li _(X) ” hydrogen storage alloy powder in a simulated negative confinement battery at room temperature.

Among them, curve 1 is the activation curve of MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 aluminum and tin two super-entropy-changing elements synergistically; curve 2 and curve 3 correspond to the activation curves of lithiation equivalent 5wt% and 3wt%, respectively. The step-by-step charging activation system is: the charging capacity of the first and second weeks of charging is 150mAh/g; the charging capacity of the third and fourth weeks is 200mAh/g; the charging capacity of the fifth to eighth weeks is 250mAh/g g; The charging capacity from the 9th to the 11th week of charging is 280mAh/g.

From the comparison of the three curves in Figure 6, it can be seen that the activation speed of the synergistic effect of the two hyper-entropy-changing elements of aluminum and tin is slightly higher than that of the synergistic effect of the three hyper-entropy-changing elements of aluminum and tin in the first and second weeks of charging. Moreover, the rest of the cycle showed similar activation rates. the

Fig. 7 is the "synergy of two hyper-entropy-changing elements of aluminum and tin--MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 " and "the synergy of three hyper-entropy-changing elements of lithium, aluminum and tin--MmNi _4.3 Al _0.3 The change curve of the maximum discharge specific capacity of Fe _0.05 Sn _0.05 -Li _(X) "hydrogen storage alloy powder at +18℃ room temperature and in the simulated negative limit battery. The curve shows that: at room temperature +18°C, the maximum discharge specific capacity of the alloy powder with the synergistic effect of two hyper-entropy-changing elements and three hyper-entropy-changing elements is above 260mAh/g as a whole, which meets the requirement of 260mAh/g for industrially available alloy powder.

Fig. 8 is the "synergy of two hyper-entropy-changing elements of aluminum and tin--MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 " and "synergy of three hyper-entropy-changing elements of lithium, aluminum and tin--MmNi _4.3 Al _0.3 Comparison curve of XRD change of Fe _0.05 Sn _0.05 -Li _(X) ” hydrogen storage alloy powder. Curve 1 is the XRD curve of MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 aluminum and tin two hyper-entropy elements synergistically acting on the hydrogen storage alloy powder; while curves 2, 3, 4, 5 and 6 correspond to lithiation equivalents of 0.5wt%, 1wt%, 2wt%, 3wt%, 4wt% and 5wt% lithium, aluminum and tin XRD curves of three hyper-entropy-changing elements synergistically acting on the hydrogen storage alloy powder; the overall characteristics of the curve change are: aluminum and tin With the addition of lithium, the synergistic effect of hyper-entropy-changing elements transforms into the synergistic action of three hyper-entropy-changing elements, lithium, aluminum and tin, especially as the addition of lithium increases, the first, second and third strong peaks are 2 times theta angle The change of the angle is not obvious, but the weak peak at 76 degrees has relatively obvious changes in peak width and peak height.

Figure 9 is a graph of a representative lithiation temperature profile of the present invention. What curve 1 among the figure provides is the actual lithiation temperature system adopted in the embodiment of the present invention 1; And what curve 2 in the figure provides is the actual lithiation temperature system adopted in the embodiment of the present invention 2; Introduce The purpose of this figure is to facilitate the intuitive understanding of the lithiation temperature regime of the present invention by examiners and colleagues. the

Detailed ways

Example 1:

Step 1: Prepare the matrix hydrogen storage alloy MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 , the preparation method of which is:

(1) Material selection: Select the metal charge according to the elements contained in the chemical formula MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 : Mm is the ingot of mixed rare earth metal, Ni is the plate of metal nickel, Al is the metal aluminum block, and Fe is the metal iron Bar, Sn is metal tin plate; the purity of all metal charge is 99.95wt%; and the composition and ratio of mixed rare earth metal composed of single rare earth are: La is 61wt%, Ce is 20wt%, Nd is 15wt% %, Pr is 4wt%.

(2) Pretreatment and batching of metal charge:

Cut the metal nickel plate into 5cm wide strips with a shearing machine; remove the oxide skin with the two kinds of charge of mixed rare earth metal ingots and iron rods, and carry out the batching according to the chemical formula of MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 , put the prepared metal charge into the induction melting furnace crucible at the same time;

(3) Induction melting and furnace crushing:

The induction melting furnace is evacuated until the vacuum degree reaches 10 ^-2 order of magnitude, then filled with argon as a protective atmosphere, and the electric power is increased until all the metal materials are melted to start timing. After 20 minutes of smelting, the temperature is maintained at 1450°C±50°C, and then cast and released from the furnace , to obtain MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 matrix hydrogen storage alloy ingot; the ingot was crushed into powder by jet milling method, and passed through a 300-mesh sieve.

During the preparation process of the matrix hydrogen storage alloy, the ultra-entropy change elements metal Al and metal Sn are added by induction melting. the

Step 2: Lithium metal is used as an ultra-entropy change reagent, and the matrix hydrogen storage alloy MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 is "lithiated" by the following method:

(1) Lithiation formula and operation: take 300 mesh MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 matrix hydrogen storage alloy powder, add 0.5 g or 1 g of metal lithium ribbon to 100 g of the powder, and put the metal lithium ribbon into the crucible Sprinkle the base hydrogen storage alloy on the bottom, cover the crucible with a lid, put it in a resistance furnace, vacuumize it with a mechanical pump until the degree of vacuum reaches 10 ^-2 order of magnitude, fill it with argon as a protective atmosphere, and start heating for lithiation.

(2) Lithiation temperature and operation: take 1.5 hours to raise the temperature to 542°C and use this as the starting point of the time to keep warm for 20 hours, then use 3 hours to raise the temperature to 903°C, and keep it at 903°C for 0.5 hours , and then cooled to room temperature to obtain lithiated MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 hydrogen storage alloy powder aggregates. The super-entropy-changing metal Li is added by a heterogeneous reaction. The lithiation temperature regime is depicted in curve 1 of accompanying drawing 9 in the form of a curve

Step 3: The hydrogen storage alloy with super-entropy change characteristics is used as the battery negative electrode alloy material Electrochemical characterization method:

After lithiation, the hydrogen storage alloy powder is ground into 300-mesh alloy powder, and the alloy powder is used as the negative electrode active material. Mix it with carbonyl Ni powder at a mass ratio of 1:6, and isostatically press it into a Φ13mm sheet as the negative electrode of the battery, and use sintered NiOOH/Ni(OH)2 as the positive electrode. The capacity of the positive electrode is 5 times greater than that of the negative electrode; between the positive and negative electrodes Separated by a nylon diaphragm, soaked in 7.5M KOH solution to form a negative-limited simulated battery, in which the weight of the electrolyte added is 25 times the weight of the added hydrogen storage alloy powder; the battery performance is tested with a DC-5 battery tester, and the connected The computer collects and processes data for the upper computer, and the ultra-low temperature refrigerator is used for low-temperature testing. The method for measuring the discharge performance of the low-temperature simulated battery is as follows: Based on the weight of the hydrogen storage alloy powder added to the simulated battery, charge the simulated battery for 5 hours at a room temperature of 60mA/g , put it in the refrigerator, and set it according to the given low temperature; freeze it in a low temperature environment for 8 hours, and then perform the discharge operation. The battery is essentially a "negative limit MH-Ni simulation experimental battery for the determination of negative active materials."

Step 4: Preparation method of hydrogen storage alloy powder for MH-Ni battery negative plate after lithiation:

The obtained lithiated MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 hydrogen storage alloy powder aggregates were smashed into pieces, and 10 grams of CMC aqueous solution with a concentration of 2wt% and a concentration of 0.8wt% were added to 100 grams of hydrogen storage alloy powder. 8 grams of PVA aqueous solution and concentration are the ratio of 7 grams of PAANa aqueous solution of 1wt%, pour this alloy powder block and three kinds of CMC, PVA, PAANa aqueous solution as binding agent into mixer and stir for 2 hours, stir the slurry of 2 hours The material was left to stand for another 2 hours, and then the static slurry was transferred to the hopper of the battery plate drawing machine, and the nickel-plated punched steel strip was used as the current collector, and the battery plate drawing machine was used for mechanical drawing , rolled, and dried to obtain a battery negative plate.

Step 5: The negative plate of the MH-Ni battery made of hydrogen storage alloy powder after lithiation will undergo a super-entropy change reaction in the MH-Ni square simulated battery Design method:

(1), the continuous battery negative plate obtained on the battery plate pulping machine is used for assembling a 100 ampere-hour square analog battery after cutting, deburring and electrochemically measuring its area specific capacity. the

(2), the positive plate of the 100 ampere-hour square analog battery selects commercially available sintered nickel anodes, and fixes the quantity of sintered nickel anode plates according to the given area specific capacity of commercially available sintered nickel anodes and makes the quantity just satisfy 100 amperes hour. the

(3) According to the design requirements of the total capacity of 170 ampere-hours, the area and size of the negative plate should be cut according to the measured electrochemical area specific capacity value and the sintered nickel anode should meet the number ratio of the negative plate plate The number of plate blocks is 1 more. the

(4) For the diaphragm, choose polypropylene non-woven cloth type battery diaphragm; repeat the stacking sequence of a sintered nickel anode plate, a layer of battery diaphragm, and then a negative electrode plate, all positive and negative plates are stacked After the completion, the tabs of the positive plate and the tabs of the negative plate are respectively welded together, and at the same time, an electrode lead-out wire is welded on each of the welded positive and negative tabs to form a square battery core. the

(5) Put the battery core into a stainless steel battery case; take the sum of the design capacity of the positive and negative electrodes as the base, that is, 270 Ah as the base, and obtain the weight value according to the product of the base and the coefficient of 1.88 Ah/g. A stainless steel battery case with a battery core is injected with a KOH aqueous solution having a concentration of 31 wt%, and then the battery case is closed. the

(6) Charge the simulated battery with a current of 10 amps for 13.5 hours, then put it in an oven and control the temperature of the oven at 50°C±1°C for 96 hours, and the AB _4.7 in the battery is non-stoichiometric The super entropy change reaction before forming the battery of the hydrogen storage alloy is all completed.

(7) Low temperature test method of 100Ah square analog battery: use ZM2030 battery charging and discharging instrument, charge the analog battery with a current of 20A at room temperature for 5.5 hours, put it in the refrigerator, and set it according to the given low temperature; Freeze in a low temperature environment for 8 hours, and then discharge the simulated battery with a current of 20A. the

After following steps 1 to 3 of this example, the discharge electrochemical gravimetric capacity measurement results of HEC alloy powder at room temperature 15°C and discharge voltage cut off to 1.0V are listed in Table 1; at low temperature 35°C 1. The discharge electrochemical gravimetric capacity measurement results when the discharge voltage is cut off to 0.9V are listed in Table 2. the

Table 1 Electrochemical gravimetric specific capacity of hyperentropy alloy powder discharged at room temperature

Table 2 Electrochemical gravimetric specific capacity of ultra-entropy-changing alloy powder at low temperature discharge

After following steps 4 to 5 of this example, use ultra-entropy alloy powder as the negative electrode active material to design and manufacture a square analog battery with a rated capacity of 100Ah. The actual discharge capacity measurement results at low temperature are listed in Table 3; the discharge capacity measurement results at a low temperature of -35°C and the discharge voltage cut-off to 0.9V are listed in Table 4. the

Table 3 Room temperature discharge capacity of super-entropy-changing alloy powder used in prismatic simulated battery

Table 4 Low-temperature discharge capacity of super-entropy-changing alloy powder used in prismatic simulated battery

Example 2:

The difference from Example 1 lies in the ratio of metal lithium bands in "Step 2——Metal lithium is an ultra-entropy change agent, "lithiated" matrix hydrogen storage alloy MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 ," in Example 1 and lithiation temperature, its specific difference with embodiment 1 is summarized as follows:

(1) Lithium formula and operation: take 300 mesh MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 matrix hydrogen storage alloy powder, add 2 grams or 3 grams or 5 grams of metal lithium strips to 100 grams of the powder, and also add metal lithium strips Put it on the bottom of the crucible, sprinkle the base hydrogen storage alloy on it, cover the upper cover of the crucible, put it in a resistance furnace, evacuate it with a mechanical pump until the vacuum degree reaches the order of 10 ^-2 , fill it with argon as a protective atmosphere, and start heating lithiation.

(2) Lithiation temperature and operation: take 1.2 hours to raise the temperature to 260°C and use this as the starting point of the time to keep warm for 18 hours, then use 3 hours to raise the temperature to 813°C, and keep it at 813°C for 1 hour , then cooled to room temperature and released from the furnace; the lithiated MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 hydrogen storage alloy powder aggregate was obtained; the super-entropy-changing element metal Li was added by a heterogeneous reaction. The lithiation temperature system is depicted in the form of a curve in the attached Curve 2 of Figure 9. All the other steps and conditions are the same as in Example 1.

The discharge electrochemical gravimetric capacity measurement results of the hyperentropy alloy powder at room temperature 15°C and discharge voltage up to 1.0V are listed in Table 5; at low temperature -35°C and discharge voltage up to 0.9V, the discharge electrochemical gravimetric ratio The results of capacity determination are listed in Table 6. the

Table 5 Electrochemical gravimetric specific capacity of hyperentropy alloy powder discharged at room temperature

Table 6 Electrochemical gravimetric specific capacity of ultra-entropy alloy powder low-temperature discharge

Using ultra-entropy alloy powder as the negative electrode active material, a square simulated battery with a rated capacity of 100Ah was designed and manufactured. The actual discharge capacity measurement results at a room temperature of 18°C and a discharge voltage cut-off of 1.0V are listed in Table 7; Table 8 lists the discharge capacity measurement results at 35°C and discharge voltage up to 0.9V. the

Table 7 The room temperature discharge capacity of super-entropy-changing alloy powder used in prismatic simulated batteries

Table 8 Low-temperature discharge capacity of super-entropy-changing alloy powder used in prismatic simulated battery

Claims (1)

1. The super entropy change method of AB _4.7 non-stoichiometric hydrogen storage alloy, which is characterized in that the steps are as follows: 1), the preparation method of base hydrogen storage alloy MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 is: according to MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 chemical formula for material selection and batching, where Mm is mixed rare earth metal ingot, Ni is metal nickel plate, Al is metal aluminum block, Fe is metal iron rod and Sn is metal tin plate, the purity of all metals 99.95wt%; the composition and proportioning of mixed rare earth metals are: La is 61wt%, Ce is 20wt%, Nd is 15wt%, and Pr is 4wt%; The mixed rare earth metal ingots and iron rods placed in the crucible of the induction melting furnace are used to remove the oxide scale; the induction melting furnace is vacuumed to a vacuum of 10 ^-2 Pa and then filled with argon as a protective atmosphere to increase the electric power Start timing until all the metal charge is melted, smelt for 20 minutes, keep the smelting temperature at 1450°C±50°C, then cast and take out the furnace to obtain the MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 matrix hydrogen storage alloy; during the preparation process of the matrix hydrogen storage alloy, The ultra-entropy-changing elements metal Al and metal Sn are added by induction melting; 2), metal lithium is the ultra-entropy-changing reagent, and the method of "lithiation" MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 matrix hydrogen storage alloy is: (1) The obtained MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 matrix hydrogen storage alloy ingot is crushed into powder by jet milling method, and passed through a 300-mesh sieve; (2) according to the weight ratio of hydrogen storage alloy powder and metal lithium strip, it is 100 grams: 0.5 Put the metal lithium strip on the bottom of the crucible, sprinkle the base hydrogen storage alloy on it, cover the upper cover of the crucible, put it in a resistance furnace, evacuate it with a mechanical pump until the vacuum degree reaches the order of 10 ^-2 Pa, and then fill it with argon Gas is used as a protective atmosphere; the electric furnace starts to heat up, and the temperature system for heating up and holding is determined as follows: take 1.5 hours to raise the temperature to 542°C and use this as the starting point of the time to count, keep the heat for 20 hours, and then use 3 hours to raise the temperature to 903°C ℃, and kept at a temperature of 903°C for 0.5 hours, then cooled to room temperature and released from the furnace to obtain lithiated MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 hydrogen storage alloy powder agglomerates; or, the hydrogen storage alloy powder described in (3) The weight ratio to the metal lithium strip is 100 grams: 1 gram; the rest are the same as (1); (4) according to the weight of the hydrogen storage alloy powder of 100 grams to 2 grams of the metal lithium strip, the metal lithium strip is placed on the bottom of the crucible, and the metal lithium strip is placed on the bottom of the crucible. Sprinkle the base hydrogen storage alloy, cover the top of the crucible, put it in a resistance furnace, evacuate it with a mechanical pump until the vacuum degree reaches the order of 10 ^-2 Pa, and then fill it with argon as a protective atmosphere; the electric furnace starts to heat up, heat up and keep warm The temperature regime is determined as : Take 1.2 hours to heat up to 260°C and use this as the starting point of the time to hold the heat for 18 hours, then use 3 hours to raise the temperature to 813°C, and keep the temperature at 813°C for 1 hour, then cool to room temperature and take out the oven; Lithiated MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 hydrogen storage alloy powder aggregates; super-entropy change element metal Li is added by heterogeneous reaction; (5) The weight ratio of the hydrogen storage alloy powder to the metal lithium strip is 100 Gram: 3 grams or 100 grams: 5 grams; the rest are the same as (4); 3), the preparation method of MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 hydrogen storage alloy powder aggregates after lithiation for MH-Ni battery negative plate : the obtained lithiated MmNi _4.3 Al _0.3 Fe _0.05 Sn _0.05 hydrogen-storage alloy powder aggregates are smashed into powder blocks, and according to 100 grams of hydrogen-storage alloy powder blocks, adding a concentration of 2wt% carboxymethylcellulose (abbreviated as CMC) aqueous solution 10 grams, a concentration of 8 grams of polyvinyl alcohol (being called for short PVA) aqueous solution of 0.8wt% and a concentration of 7 grams of crosslinked polyacrylic acid sodium (being called for short PAANa) aqueous solution of 1wt% are proportioned, the alloy powder block and three A kind of CMC, PVA, PAANa aqueous solution as binder is poured into the mixer and stirred for 2 hours, and then left to stand for 2 hours, then transferred to the hopper of the battery plate pulling machine, with the nickel-plated punching steel strip as the current collector, Mechanical pulping, rolling, and drying are carried out by the battery plate pulling machine to obtain the negative plate of the battery; 4), the design method for the negative plate of the battery to undergo hyperentropy change reaction again in the MH-Ni simulated battery: (1 ), the negative plate of the battery obtained in step (3) is cut, deburred, and used for assembling a 100-ampere-hour square analog battery after electrochemically measuring its area specific capacity; (2), the selection of the positive plate of the 100-ampere-hour square analog battery Commercially available sintered nickel anodes, and fix the number of sintered nickel anode plates according to the given area specific capacity of commercially available sintered nickel anodes so that the number just meets 100 ampere hours; (3), the battery negative plate is 170 amperes according to the total capacity design, and then convert the area of the negative plate of the battery according to the measured electrochemical area specific capacity value to meet the requirement that the number of negative plate plates is one more than the number of sintered nickel anode plate plates; (4), select Polypropylene non-woven fabric battery separator; repeat the stacking order of a sintered nickel anode plate, a layer of polypropylene non-woven fabric battery separator, and then a negative electrode plate. All positive and negative plates are stacked After the completion, the tabs of the positive plate and the tabs of the negative plate are respectively welded together, and at the same time, an electrode lead-out wire is respectively welded on the welded positive and negative tabs to form a square battery core; (5), the Put the battery core in the stainless steel battery case; take the sum of the design capacity of the positive and negative electrodes as the base number, that is, 270 Ah as the base number, and obtain the weight value according to the product of the base number and the 1.88 Ah/g coefficient. The injection concentration in the stainless steel battery case is 31wt% (6) Charge the simulated battery with a current of 10 amps for 13.5 hours, and then put it in an oven at a constant temperature of 50°C±1°C for 96 hours. The super entropy change reaction of the AB _4.7 non-stoichiometric hydrogen storage alloy battery before forming is all completed.

Images