Negative hydrogen storage material, its preparation method and nickel-hydrogen battery containing the negative hydrogen storage material

Abstract

The application provides a negative electrode hydrogen storage material, a preparation method thereof and a nickel-hydrogen battery containing the negative electrode hydrogen storage material. The method comprises the following steps: mixing a rare earth AB5 type hydrogen storage alloy powder and an amorphous FeTi-based alloy powder to obtain a composite alloy powder; adding the composite alloy powder into a carbon nanotube-polyethyleneimine dispersion liquid to obtain a first mixture; adding cerium oxide, lanthanum oxide, niobium pentoxide, graphene and conductive carbon black into a second solvent to obtain an additive dispersion liquid; adding the additive dispersion liquid into the first mixture to obtain a second mixture; adding polytetrafluoroethylene into the second mixture to obtain a negative electrode slurry; coating the negative electrode slurry on a current collector, drying and then pressing to obtain a negative electrode sheet and performing vacuum drying on the negative electrode sheet. The negative electrode hydrogen storage material improves hydrogen diffusion and electrochemical reaction kinetics at low temperature, alleviates the problems of battery polarization increase and capacity attenuation in an ultralow-temperature environment, and improves the cycle stability of the electrode.

Description

Technical Field

[0001] This invention belongs to the field of electrochemical energy storage battery material technology, specifically relating to a negative electrode hydrogen storage material, its preparation method, and a nickel-metal hydride battery containing the negative electrode hydrogen storage material. Background Technology

[0002] Nickel-metal hydride (NiMH) batteries, as green and environmentally friendly alkaline rechargeable batteries, possess outstanding advantages such as no memory effect, safe charging and discharging, excellent cycle life, and resistance to overcharge and over-discharge. They are now widely used in power tools, hybrid vehicles, rail transportation, and civilian energy storage devices. They are also core energy storage power sources for extreme operating conditions such as polar scientific research, high-altitude communications, aerospace, and military special equipment. The negative electrode hydrogen storage alloy is a key material determining the electrochemical performance of NiMH batteries. During charging and discharging, energy storage and release are completed through the reversible absorption and desorption of hydrogen by the alloy. Its hydrogen storage capacity, hydrogen diffusion rate, low-temperature reaction kinetics, and corrosion resistance directly determine the battery capacity, rate performance, and service life.

[0003] The current mainstream commercial anode material is the rare-earth AB5 hydrogen storage alloy. This system has low activation difficulty, good overall cycle stability, and is suitable for use in normal room temperature environments. However, it has significant shortcomings: when the ambient temperature drops to -40℃ and below, the diffusion coefficient of hydrogen atoms in the bulk phase of the alloy decreases significantly, the activation energy of electrochemical reactions on the electrode surface increases sharply, the battery polarization becomes severe, and the discharge capacity drops precipitously. Conventional AB5 alloys have a discharge capacity of only 30%-50% of their room temperature capacity at -40℃, and essentially lose their discharge capacity when the temperature drops to -60℃, making it unable to support the continuous power supply needs of special equipment in high-altitude, polar, and deep-space environments.

[0004] Existing research has explored low-temperature hydrogen storage materials. Some studies have developed neodymium-free, wide-temperature-range rare-earth alloys that can achieve a certain capacity output at -40℃, but their performance degrades significantly below -50℃. Although A2B7 type superlattice hydrogen storage alloys have higher capacity at room temperature, their reaction kinetics are extremely poor at low temperatures, and their capacity is almost non-existent at -45℃. There are also non-AB5 type low-temperature alloy systems that have improved low-temperature performance, but their preparation costs are high, and they are prone to pulverization and corrosion during long-term cycling in alkaline electrolytes, making industrialization difficult.

[0005] Based on the current state of technology, existing single-element hydrogen storage alloy systems generally suffer from low low-temperature hydrogen diffusion rates and sluggish interfacial reaction kinetics. Most modification schemes only optimize conductivity or the hydrogen storage matrix, failing to simultaneously construct a low-temperature catalytic system, a long-lasting anti-corrosion coating, and a multi-scale continuous conductive network. This makes it difficult to simultaneously achieve high room-temperature capacity, excellent ultra-low-temperature discharge capability, and long-cycle stability. Currently, there is a lack of negative electrode hydrogen storage materials that can stably adapt to the entire low-temperature operating range of -40℃ to -60℃, which greatly limits the engineering application of special low-temperature nickel-metal hydride batteries in polar, military, and aerospace fields.

[0006] Therefore, there is an urgent need to develop a new composite hydrogen storage material system and its supporting preparation process to solve the industry pain points such as the precipitous capacity decay at low temperatures, easy corrosion and pulverization of alloys, and insufficient cycle life of traditional materials. Summary of the Invention

[0007] This invention aims to solve one or more of the problems encountered in the prior art. Specifically, the purpose of this invention is to overcome the shortcomings of existing hydrogen storage anode materials, such as slow hydrogen diffusion, poor electrochemical reaction kinetics, significant discharge capacity decay, easy corrosion and pulverization of alloys, and insufficient cycle stability at ultra-low temperatures of -40℃ to -60℃. By constructing a composite system of AB5 rare earth hydrogen storage alloy and amorphous FeTi-based alloy, combined with multi-element low-temperature catalysts and modified conductive materials, a multi-layered synergistic structure is formed, improving low-temperature reaction efficiency, balancing hydrogen storage capacity and cycle life, and providing anode hydrogen storage materials, preparation methods, and matching nickel-metal hydride batteries suitable for extreme low-temperature operating conditions, meeting the power supply needs of special equipment in polar regions, military, aerospace, and other fields.

[0008] Specifically, according to one aspect of the present invention, a method for preparing a negative electrode hydrogen storage material is provided, the method comprising the following steps: (1) Mix rare earth-based AB5 type hydrogen storage alloy powder and amorphous FeTi-based alloy powder to obtain composite alloy powder; (2) Disperse carbon nanotubes in a first solvent, then add polyethyleneimine and perform ultrasonic dispersion to obtain a carbon nanotube-polyethyleneimine dispersion. (3) Add the composite alloy powder obtained in step (1) to the carbon nanotube-polyethyleneimine dispersion obtained in step (2), stir and mix to obtain the first mixture; (4) Add cerium oxide, lanthanum oxide, niobium pentoxide, graphene and conductive carbon black to the second solvent and disperse them by ultrasonication to obtain an additive dispersion, wherein the weight ratio of cerium oxide to lanthanum oxide is in the range of 1:3-1:8 and the weight ratio of cerium oxide to niobium pentoxide is in the range of 1:2-1:5. (5) Add the additive dispersion obtained in step (4) to the first mixture obtained in step (3), stir and mix to obtain the second mixture; (6) Prepare a water dispersion of polytetrafluoroethylene binder, add it to the second mixture obtained in step (5), stir and mix to obtain a negative electrode slurry; (7) Coat the negative electrode slurry obtained in step (6) onto the current collector, dry it and press it into shape to obtain a negative electrode sheet; (8) The negative electrode sheet obtained in step (7) is vacuum dried to obtain the negative electrode hydrogen storage material.

[0009] According to certain preferred embodiments of the present invention, the weight ratio of cerium oxide to lanthanum oxide is in the range of 1:4 to 1:6, and the weight ratio of cerium oxide to niobium pentoxide is in the range of 1:3 to 1:4.

[0010] According to certain preferred embodiments of the present invention, based on 100% of the total weight of the remaining portion of the negative electrode hydrogen storage material excluding the current collector, the amounts of each component are as follows: 60-75% by weight of rare earth-based AB5 type hydrogen storage alloy powder; 15-20% by weight of amorphous FeTi-based alloy powder; 2-6% by weight of carbon nanotubes; 1-3% by weight of polyethyleneimine; The sum of 1.5-5% by weight of cerium oxide, lanthanum oxide and niobium pentoxide; 0.5-2% by weight of graphene; 1-3% by weight of conductive carbon black; 2-5% by weight of polytetrafluoroethylene adhesive.

[0011] According to certain preferred embodiments of the present invention, the general chemical formula of the rare earth-based AB5 type hydrogen storage alloy powder is La. 1-x Ce x Ni 5-y-z-w Co y Mn z Al w Where: x ranges from 0.15 to 0.35; y ranges from 0.3 to 0.6; z ranges from 0.3 to 0.5; and w ranges from 0.2 to 0.4.

[0012] According to certain preferred embodiments of the present invention, the rare earth-based AB5 type hydrogen storage alloy powder is prepared by the following steps: (a) The metal raw materials La, Ce, Ni, Co, Mn and Al are weighed according to the stoichiometric ratio of the general chemical formula and melted in a vacuum induction melting furnace under argon protection at 1500-1600°C to obtain an alloy liquid; (b) The molten alloy is poured into a water-cooled copper mold to obtain an alloy ingot; (c) The alloy ingot is subjected to homogenization annealing at 1000-1100°C in an argon atmosphere for 8-15 hours to obtain the annealed alloy ingot. (d) The alloy ingot is crushed and ball-milled to obtain alloy powder with a particle size of 30-50 μm.

[0013] According to certain preferred embodiments of the present invention, the amorphous FeTi-based alloy powder has the general chemical formula FeTi. 1.2-a-b Ma N b Where: M is a transition metal element Co and / or Ni; N is a rare earth element Y and / or Gd; the value of a ranges from 0.05 to 0.15; and the value of b ranges from 0.02 to 0.08.

[0014] According to certain preferred embodiments of the present invention, the amorphous FeTi-based alloy powder is prepared by the following steps: (a) Fe, Ti, Co, Ni, Y, and Gd metal raw materials are prepared under argon protection according to the stoichiometric ratio of the general chemical formula; (b) Place the prepared raw materials and stainless steel grinding balls in a planetary ball mill at a ball-to-material ratio of 15:1-25:1, and ball mill for 40-60 hours under argon protection and a speed of 400-500 rpm to obtain amorphous alloy powder. (c) The amorphous alloy powder is sieved to obtain alloy powder with a particle size of 25-45 μm.

[0015] According to certain preferred embodiments of the present invention, in step (1), the mixing is ball milling, the ball-to-material ratio is 10:1-30:1, the rotation speed is 200-400 rpm, the mixing time is 2-6 hours, and the mixing process is carried out under argon atmosphere protection.

[0016] According to certain preferred embodiments of the present invention, the carbon nanotubes are modified multi-walled carbon nanotubes.

[0017] According to certain preferred embodiments of the present invention, the modified carbon nanotubes are prepared by the following steps: (a) Calcine multi-walled carbon nanotubes in an inert gas at 400-500℃ for 2-4 hours; (b) Immerse the calcined carbon nanotubes in a mixture of concentrated sulfuric acid and concentrated nitric acid, and reflux at 60-80°C for 6-12 hours. (c) Wash the acid-treated carbon nanotubes until neutral, and then dry them; (d) The dried carbon nanotubes were placed in a low-temperature plasma treatment device and subjected to plasma treatment in an oxygen atmosphere. (e) The plasma-treated carbon nanotubes were immersed in a mixed aqueous solution containing Ni(NO3)2 and Co(NO3)2 and then subjected to ultrasonic treatment. (f) The product obtained in step (e) is reduced in a hydrogen atmosphere to obtain the modified carbon nanotubes.

[0018] According to certain preferred embodiments of the present invention, in step (b), the volume ratio of concentrated sulfuric acid to concentrated nitric acid in the mixed acid is 2:1 to 4:1.

[0019] According to certain preferred embodiments of the present invention, in step (c), the drying temperature is 80-100°C and the drying time is 12-24 hours.

[0020] According to certain preferred embodiments of the present invention, in step (d), the power of the plasma treatment is 100-200W, the oxygen flow rate is 50-100mL / min, and the treatment time is 20-40 minutes.

[0021] According to certain preferred embodiments of the present invention, in step (e), the concentration of Ni(NO3)2 is 0.5-1.5 mol / L, and the concentration of Co(NO3)2 is 0.1-0.5 mol / L.

[0022] According to certain preferred embodiments of the present invention, in step (e), the mixed aqueous solution further contains Y(NO3)3, wherein the concentration of Y(NO3)3 is 0.05-0.2 mol / L.

[0023] According to certain preferred embodiments of the present invention, in step (e), the ultrasonic treatment time is 2-4 hours.

[0024] According to certain preferred embodiments of the present invention, in step (f), the reduction treatment is carried out at a temperature of 400-500°C for 2-4 hours.

[0025] According to certain preferred embodiments of the present invention, the weight-average molecular weight of the polyethyleneimine is 600-25000.

[0026] According to certain preferred embodiments of the present invention, the first solvent is deionized water.

[0027] According to certain preferred embodiments of the present invention, in the carbon nanotube-polyethyleneimine dispersion, the total weight of carbon nanotubes and polyethyleneimine accounts for 6-17% by weight.

[0028] According to certain preferred embodiments of the present invention, in step (2), the ultrasonic dispersion power is 200-400W, the frequency is 40-60 kHz, and the dispersion time is 30-60 minutes.

[0029] According to certain preferred embodiments of the present invention, the average particle size of cerium oxide is in the range of 5-100 nm, the average particle size of lanthanum oxide is in the range of 40-100 nm, the average particle size of niobium pentoxide is in the range of 50-200 nm, the average particle size of graphene is in the range of 2-30 nm, and the average particle size of conductive carbon black is in the range of 20-100 nm.

[0030] According to certain preferred embodiments of the present invention, the surface of the graphene contains one or more of hydroxyl, carboxyl, and amino groups.

[0031] According to certain preferred embodiments of the present invention, the second solvent is deionized water.

[0032] According to certain preferred embodiments of the present invention, the total weight of cerium oxide, lanthanum oxide, niobium pentoxide, graphene and conductive carbon black in the additive dispersion accounts for 3-10% by weight.

[0033] According to certain preferred embodiments of the present invention, in step (4), the power of the ultrasonic dispersion is 200-500W, the frequency is 30-60 kHz, and the time is 15-45 minutes.

[0034] According to certain preferred embodiments of the present invention, the solid content of the aqueous dispersion of the polytetrafluoroethylene adhesive is 30-50% by weight.

[0035] According to certain preferred embodiments of the present invention, in step (6), the stirring and mixing time is 1-2 hours.

[0036] According to certain preferred embodiments of the present invention, the current collector is a nickel foam current collector.

[0037] According to certain preferred embodiments of the present invention, the thickness of the nickel foam current collector is in the range of 1-2 mm, and the porosity is 80-95%.

[0038] According to certain preferred embodiments of the present invention, the coating thickness of the negative electrode slurry is in the range of 0.5-1.0 mm.

[0039] According to certain preferred embodiments of the present invention, in step (7), the drying includes drying under vacuum at a temperature of 60-80°C for 8-12 hours.

[0040] According to certain preferred embodiments of the present invention, in step (7), the pressure of the compression molding is 5-15 MPa.

[0041] According to certain preferred embodiments of the present invention, in step (8), the vacuum drying temperature is 120-150°C and the time is 2-4 hours.

[0042] According to another aspect of the present invention, a negative electrode hydrogen storage material is provided, which is prepared by the preparation method described above.

[0043] According to certain preferred embodiments of the present invention, the negative electrode hydrogen storage material comprises: Current collector; and The hydrogen storage material on the current collector, the hydrogen storage material comprising, based on its total weight of 100%, the following: 60-75% by weight of rare earth-based AB5 type hydrogen storage alloy powder; 15-20% by weight of amorphous FeTi-based alloy powder; 2-6% by weight of carbon nanotubes; 1-3% by weight of polyethyleneimine; The sum of 1.5-5% by weight of cerium oxide, lanthanum oxide and niobium pentoxide; 0.5-2% by weight of graphene; 1-3% by weight of conductive carbon black; 2-5% by weight of polytetrafluoroethylene adhesive.

[0044] According to another aspect of the present invention, a nickel-metal hydride battery is provided, the nickel-metal hydride battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the negative electrode comprises the negative electrode hydrogen storage material described above.

[0045] According to certain preferred embodiments of the present invention, the positive electrode is a cobalt-coated spherical nickel hydroxide positive electrode.

[0046] According to certain preferred embodiments of the present invention, the diaphragm is a sulfonated polypropylene diaphragm.

[0047] According to certain preferred embodiments of the present invention, the electrolyte is a mixed alkaline solution containing KOH, NaOH and LiOH, wherein the concentration of KOH is 5.0-7.0 mol / L, the concentration of NaOH is 0.5-1.5 mol / L, and the concentration of LiOH is 0.5-1.5 mol / L.

[0048] Compared with existing technologies, the beneficial effects of this invention are as follows: First, it employs a dual hydrogen storage matrix of rare-earth-based AB5-type hydrogen storage alloy powder combined with amorphous FeTi-based alloy powder. This leverages the amorphous disordered structure to broaden hydrogen diffusion channels, improving electrochemical reaction kinetics at ultra-low temperatures of -40℃ to -60℃ and significantly alleviating the problem of rapid capacity drop at low temperatures. Second, by introducing Nb2O5, CeO2, and La2O3 to form a low-temperature catalytic system with carbon nanotubes, it synergistically reduces the activation energy of the reaction and increases the electrode exchange current density. Third, the multi-layered coating structure formed by the polyethyleneimine inner layer, the catalyst intermediate layer, and the carbon nanotube / graphene outer layer effectively blocks alkaline electrolytes, inhibits alloy corrosion and pulverization, and extends cycle life. Fourth, carbon nanotubes, graphene, and conductive carbon black construct a multi-scale three-dimensional conductive network, ensuring efficient electron conduction at low temperatures. The overall material balances high room-temperature hydrogen storage capacity, excellent extreme low-temperature discharge performance, and stable cycle characteristics. The preparation process is simple and easy to mass-produce, making it suitable for ultra-low temperature special nickel-metal hydride battery applications in polar regions, aerospace, and military industries. Attached Figure Description

[0049] The accompanying drawings are provided in this specification to more clearly explain the technical solutions of the present invention; however, the art is not limited thereto.

[0050] Figure 1 A flowchart illustrating the preparation process of the negative electrode hydrogen storage material according to the technical solution of the present invention is shown. Detailed Implementation

[0051] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. It will be understood that other embodiments may be implemented without departing from the scope or spirit of the invention. Therefore, the following detailed description is non-limiting.

[0052] Unless otherwise specified, all figures used in this specification to represent characteristic dimensions, quantities, and physical properties should be understood to be modified by the term "about" in all cases. Therefore, unless otherwise stated, the numerical parameters listed in the foregoing specification are approximations, and those skilled in the art can appropriately modify these approximations to obtain the desired properties using the teachings disclosed herein.

[0053] As mentioned above, existing nickel-metal hydride battery anode hydrogen storage materials face several technical challenges when used in ultra-low temperature environments ranging from -40°C to -60°C. Traditional commercial AB5-type hydrogen storage alloys exhibit a significant decrease in hydrogen diffusion rate at low temperatures, an increase in electrochemical reaction activation energy, and intensified battery polarization. This results in substantial capacity decay at -40°C and near-complete loss of discharge capability at -60°C. Conventional modification schemes lack multi-layered protective structures, making the alloy prone to pulverization and failure during charge and discharge processes. Furthermore, single conductive agents struggle to form continuous conductive pathways at low temperatures. Existing technologies cannot simultaneously achieve high room-temperature hydrogen storage capacity, wide-range ultra-low temperature discharge performance, and long cycle life, failing to meet the power supply requirements of extreme cryogenic equipment in polar regions, military applications, and aerospace. This invention aims to solve one or more of the above problems.

[0054] Specifically, according to one aspect of the present invention, a method for preparing a negative electrode hydrogen storage material is provided, wherein: firstly, rare earth-based AB5 type hydrogen storage alloy powder is mixed with amorphous FeTi-based alloy powder to obtain a composite alloy powder. Then, carbon nanotubes are dispersed in a solvent and ultrasonically treated with polyethyleneimine to prepare a composite dispersion, which is then mixed into the composite alloy powder and stirred to form a mixture. Subsequently, cerium oxide, lanthanum oxide, and niobium pentoxide are formulated according to a defined ratio, and graphene and conductive carbon black are added and ultrasonically treated with a solvent to obtain an additive dispersion, which is then incorporated into the aforementioned mixture and mixed thoroughly. Next, a polytetrafluoroethylene aqueous dispersion is added to prepare a negative electrode slurry, which is coated onto the surface of a current collector, dried, pressed into shape, and then vacuum dried to finally obtain the finished negative electrode hydrogen storage material. This method, through the synergistic modification of multi-element alloy compounding and functional additives, can effectively improve the hydrogen storage performance and conductivity stability of the material.

[0055] Figure 1 A flowchart illustrating the preparation process of a negative electrode hydrogen storage material according to the present invention is shown, which specifically includes the following steps: (1) Mix rare earth-based AB5 type hydrogen storage alloy powder and amorphous FeTi-based alloy powder to obtain composite alloy powder; (2) Disperse carbon nanotubes in a first solvent, then add polyethyleneimine and perform ultrasonic dispersion to obtain a carbon nanotube-polyethyleneimine dispersion. (3) Add the composite alloy powder to the carbon nanotube-polyethyleneimine dispersion and stir to mix to obtain the first mixture; (4) Add cerium oxide, lanthanum oxide, niobium pentoxide, graphene and conductive carbon black to the second solvent and disperse them by ultrasonication to obtain an additive dispersion. (5) Add the additive dispersion to the first mixture and stir to mix to obtain the second mixture; (6) Prepare a water dispersion of polytetrafluoroethylene binder, add it to the second mixture, stir and mix to obtain negative electrode slurry; (7) Coat the negative electrode slurry onto the current collector, dry it, and then press it into shape to obtain a negative electrode sheet; (8) The negative electrode sheet is vacuum dried to obtain the negative electrode hydrogen storage material.

[0056] This invention breaks through the technical limitations of traditional single hydrogen storage alloy systems. It innovatively adopts a dual-alloy matrix composite modification process, combining functional conductive additives, low-temperature catalytic components, and multi-layer protective structures for synergistic optimization. It simultaneously addresses the core pain points of existing nickel-metal hydride battery anode materials from four dimensions: hydrogen storage matrix, interfacial catalysis, conductive network, and corrosion protection. These pain points include low-temperature kinetic lag, severe capacity decay, easy alloy pulverization and corrosion, and poor cycle stability. Among them, the dual-alloy compounding in step (1) is the core foundation for ensuring the wide-temperature hydrogen storage performance of the material. Relying on the excellent room-temperature hydrogen storage capacity, activation performance, and cycle stability of rare earth AB5 hydrogen storage alloy, and combined with the unique disordered atomic structure of amorphous FeTi-based alloy, the diffusion channels of hydrogen atoms under low-temperature conditions are greatly broadened, the hydrogen migration energy barrier is reduced, and the problems of the sudden drop in hydrogen diffusion coefficient and excessively high electrochemical reaction activation energy of traditional AB5 alloy at ultra-low temperatures of -40℃ to -60℃ are solved. The carbon nanotube-polyethyleneimine composite dispersion system constructed in step (2) can achieve uniform dispersion of conductive materials and preliminary coating of alloy particles. The polymer chain structure of polyethyleneimine can enhance the interfacial bonding force between carbon nanotubes and alloy powder, and at the same time form a preliminary insulating protective layer to block the erosion of the alloy matrix by alkaline electrolyte. Step (4) provides a ternary metal oxide catalytic system, which, combined with multidimensional carbon-based conductive additives, can construct efficient low-temperature catalytic reaction sites at the electrode interface, synergistically reduce the activation energy of electrochemical reactions, increase the electrode exchange current density at ultra-low temperatures, and improve the defects of severe battery polarization and precipitous drop in discharge capacity. With the synergistic cooperation of each step, the final prepared negative electrode hydrogen storage material can take into account high room temperature hydrogen storage capacity, excellent ultra-low temperature discharge performance and ultra-long cycle life, and is suitable for the power supply needs of extreme low temperature working conditions such as polar scientific research, aerospace, and military special equipment.

[0057] Rare earth-based AB5-type hydrogen storage alloy powder is a relatively mature material in the field of nickel-metal hydride battery anodes. In this invention, there is no particular limitation on the specific type of rare earth-based AB5-type hydrogen storage alloy powder used. This rare earth-based AB5-type hydrogen storage alloy powder can be commercially available or prepared according to the methods described in existing technical documents (e.g., Chinese Patent Publication Nos. CN118431456A, CN1438343A, CN117208844A, and CN117615868A). According to certain preferred embodiments of the present invention, in step (1), the general chemical formula of the rare earth-based AB5-type hydrogen storage alloy powder is La. 1-x Ce x Ni 5-y-z-w Co y Mn z Al wWhere: x ranges from 0.15 to 0.35; y ranges from 0.3 to 0.6; z ranges from 0.3 to 0.5; and w ranges from 0.2 to 0.4. This invention optimizes the crystal structure, hydrogen storage performance, and corrosion resistance of AB5 type rare earth alloys by precisely controlling the element doping ratio. Specifically, Ce partially replaces La, refining the alloy grains, improving the alloy's structural density, and simultaneously enhancing the alloy's surface's oxidation and corrosion resistance, reducing the erosion of the alloy matrix by alkaline electrolytes. Co, Mn, and Al doping modification effectively controls the alloy's lattice constant and lattice stress, optimizes hydrogen atom insertion / extraction kinetics, reduces hydrogen diffusion resistance, and simultaneously suppresses lattice distortion and pulverization failure during charge-discharge cycles.

[0058] According to certain preferred embodiments of the present invention, the rare earth-based AB5 type hydrogen storage alloy powder is prepared by the following steps: (a) La, Ce, Ni, Co, Mn, and Al metal raw materials are weighed according to the stoichiometric ratio of the general chemical formula and melted in a vacuum induction melting furnace under argon protection at 1500-1600℃ to obtain an alloy liquid; (b) the alloy liquid is poured into a water-cooled copper mold to obtain an alloy ingot; (c) the alloy ingot is subjected to homogenization annealing treatment at 1000-1100℃ in an argon atmosphere for 8-15 hours to obtain an annealed alloy ingot; (d) the alloy ingot is crushed and ball-milled to obtain alloy powder with a particle size of 30-50 μm. The above preparation process is the optimal preparation process adapted to the composite modification system of the present invention.

[0059] Amorphous FeTi-based alloy powder is a hydrogen storage material with a unique disordered atomic structure, prepared through a special process (such as mechanical alloying). In this invention, there are no particular limitations on the specific type of amorphous FeTi-based alloy powder used. This amorphous FeTi-based alloy powder can be commercially available or prepared according to methods described in existing technical documents (e.g., Chinese Patent Publication No. CN103834822A and Chinese Patent Publication No. CN101817087A). According to certain preferred embodiments of the present invention, in step (1), the general chemical formula of the amorphous FeTi-based alloy powder is FeTi. 1.2-a-b M a N bWhere: M is a transition metal element Co and / or Ni; N is a rare earth element Y and / or Gd; the value of a ranges from 0.05 to 0.15; and the value of b ranges from 0.02 to 0.08. Amorphous FeTi-based alloys are an important modified matrix for achieving breakthroughs in ultra-low temperature performance in this invention. Their irregular amorphous atomic structure lacks grain boundary resistance, which can greatly reduce the diffusion barrier of hydrogen atoms at ultra-low temperatures, solving the technical bottleneck of hindered hydrogen diffusion at low temperatures in traditional crystalline alloys. This invention further optimizes the low-temperature hydrogen storage and electrochemical performance of amorphous FeTi alloys through co-doping modification with Co and Ni transition metals and Y and Gd rare earth elements: Co and Ni elements can improve the electronic conductivity and electrochemical reactivity of the alloy, and optimize the interface charge transport efficiency; Y and Gd rare earth elements can stabilize the amorphous disordered structure, inhibit the transformation of the amorphous structure to a crystalline state during charging and discharging, and avoid low-temperature performance degradation.

[0060] According to certain preferred embodiments of the present invention, the amorphous FeTi-based alloy powder is prepared by the following steps: (a) Fe, Ti, Co, Ni, Y, and Gd metal raw materials are mixed according to the stoichiometric ratio of the general chemical formula under argon protection; (b) the mixed raw materials and stainless steel grinding balls are placed in a planetary ball mill at a ball-to-material ratio of 15:1-25:1 and ball-milled for 40-60 hours under argon protection and a rotation speed of 400-500 rpm to obtain amorphous alloy powder; (c) the amorphous alloy powder is sieved to obtain alloy powder with a particle size of 25-45 μm. The present invention uses a high-energy mechanical alloying process to prepare amorphous FeTi-based alloys. Compared with traditional smelting processes, it can efficiently prepare pure amorphous powders with uniform structure and controllable defects. The process is simple, cost-controllable, and suitable for mass production.

[0061] According to certain preferred embodiments of the present invention, in step (1), the mixing is ball milling, the ball-to-material ratio is 10:1-30:1, the rotation speed is 200-400 rpm, the mixing time is 2-6 hours, and the mixing process is carried out under argon atmosphere protection.

[0062] According to certain preferred embodiments of the present invention, in step (2), the carbon nanotubes are modified multi-walled carbon nanotubes. Compared with ordinary carbon nanotubes, the modified multi-walled carbon nanotubes used in the present invention have undergone structural activation, functional group modification and metal loading modification, which solves the defects of ordinary carbon nanotubes such as easy agglomeration, weak interfacial bonding with alloy powder and poor dispersibility.

[0063] It should be noted that there are no particular limitations on carbon nanotubes in this invention. Modified multi-walled carbon nanotubes are preferred. There are no particular limitations on the modification method of carbon nanotubes, and modification can be carried out according to the modification methods described in existing technical literature (e.g., Chinese Patent Publication No. CN110894579A). According to certain preferred embodiments of the present invention, the modified carbon nanotubes are prepared by the following steps: (a) calcining multi-walled carbon nanotubes in an inert gas at 400-500°C for 2-4 hours; (b) immersing the calcined carbon nanotubes in a mixed acid of concentrated sulfuric acid and concentrated nitric acid, and refluxing at 60-80°C for 6-12 hours; (c) washing the acid-treated carbon nanotubes until neutral, and then drying them; (d) placing the dried carbon nanotubes in a low-temperature plasma treatment device and performing plasma treatment in an oxygen atmosphere; (e) immersing the plasma-treated carbon nanotubes in a mixed aqueous solution containing Ni(NO3)2 and Co(NO3)2, and ultrasonically treating them; (f) reducing the product obtained in step (e) in a hydrogen atmosphere to obtain the modified carbon nanotubes.

[0064] According to some preferred embodiments of the present invention, in step (b), the volume ratio of concentrated sulfuric acid to concentrated nitric acid in the mixed acid is 2:1-4:1. According to some preferred embodiments of the present invention, in step (c), the drying temperature is 80-100°C, and the drying time is 12-24 hours. According to some preferred embodiments of the present invention, in step (d), the plasma treatment power is 100-200W, the oxygen flow rate is 50-100mL / min, and the treatment time is 20-40 minutes. According to some preferred embodiments of the present invention, in step (e), the concentration of Ni(NO3)2 is 0.5-1.5 mol / L, and the concentration of Co(NO3)2 is 0.1-0.5 mol / L. According to some preferred embodiments of the present invention, in step (e), the mixed aqueous solution further contains Y(NO3)3, and the concentration of Y(NO3)3 is 0.05-0.2 mol / L. The introduction of trace amounts of rare earth element Y can help modify the active sites on the surface of carbon nanotubes, stabilize the supported Ni and Co metal nanoparticles, inhibit the migration, aggregation, and detachment of metal particles during charge-discharge cycles, and improve the long-term catalytic stability of the modified carbon nanotubes. According to some preferred embodiments of the present invention, in step (e), the ultrasonic treatment time is 2-4 hours. According to some preferred embodiments of the present invention, in step (f), the reduction treatment temperature is 400-500℃, and the time is 2-4 hours.

[0065] According to certain preferred embodiments of the present invention, in step (2), the weight-average molecular weight of the polyethyleneimine is 600-25000.

[0066] According to certain preferred embodiments of the present invention, in step (2), the first solvent is deionized water. Using deionized water as the dispersion solvent results in no impurity residue, low cost, and environmental friendliness. It is compatible with water-soluble dispersion systems of polyethyleneimine and modified carbon nanotubes, avoiding the problems of increased electrode internal resistance and performance degradation caused by organic solvent residue. Simultaneously, it meets the industrialization requirements of the aqueous preparation process for nickel-metal hydride batteries.

[0067] According to certain preferred embodiments of the present invention, in step (2), the total weight of carbon nanotubes and polyethyleneimine in the carbon nanotube-polyethyleneimine dispersion is 6-17% by weight. This solid content range can ensure that the dispersion has excellent fluidity and dispersion stability, which can achieve uniform loading and coating of modified carbon nanotubes and polyethyleneimine on the surface of alloy powder, and avoid insufficient coating and poor modification effect due to too low solid content, or excessive solid content leading to viscous dispersion and severe agglomeration, affecting the subsequent slurry mixing and coating molding quality.

[0068] According to certain preferred embodiments of the present invention, in step (2), the ultrasonic dispersion power is 200-400W, the frequency is 40-60 kHz, and the dispersion time is 30-60 minutes.

[0069] According to certain preferred embodiments of the present invention, in step (4), the weight ratio of cerium oxide to lanthanum oxide is in the range of 1:4 to 1:6, and the weight ratio of cerium oxide to niobium pentoxide is in the range of 1:3 to 1:4. It should be noted that the ratio of ternary metal oxides is an important parameter determining the ultra-low temperature catalytic performance of the material. Cerium oxide can effectively regulate the electron transport characteristics of the electrode interface through its abundant oxygen vacancy structure, reducing the activation energy of hydrogen adsorption and desorption reactions; lanthanum oxide can optimize the hydrogen adsorption sites on the alloy surface, improving the adsorption capacity and adsorption stability of hydrogen atoms; niobium pentoxide has excellent proton conduction ability, which can accelerate the diffusion and migration of hydrogen atoms in the bulk phase and interface of the alloy. When the ratio of cerium oxide to lanthanum oxide and niobium pentoxide is within the preferred range of the present invention, the three can form a complementary and synergistic low-temperature catalytic system, maximizing the activation of electrochemical reaction activity at ultra-low temperatures. If the proportion of cerium oxide is too high, it will lead to oxide agglomeration and accumulation, covering the active sites of the alloy and hindering electrolyte wetting and hydrogen diffusion; if the proportion of cerium oxide is too low, the number of oxygen vacancies will be insufficient, and the catalytic activation effect will be greatly weakened.

[0070] According to certain preferred embodiments of the present invention, in step (4), the average particle size of cerium oxide is in the range of 5-100 nm, the average particle size of lanthanum oxide is in the range of 40-100 nm, the average particle size of niobium pentoxide is in the range of 50-200 nm, the average particle size of graphene is in the range of 2-30 nm, and the average particle size of conductive carbon black is in the range of 20-100 nm. The present invention achieves hierarchical filling and uniform loading of catalytic promoters and carbon-based conductive materials through multi-scale particle size matching design. Nanoscale oxide catalytic promoters can precisely adhere to the surface of alloy powders, constructing high-density low-temperature catalytic sites; ultra-small particle size graphene can fill the tiny gaps in the powder, constructing thin-layer conductive pathways; conductive carbon black can fill large-size voids, perfecting the three-dimensional conductive network. The multi-scale complementary particle size structure can maximize the improvement of electrode conductivity uniformity, catalytic site density, and electrolyte transport efficiency, completely solving the problem of hindered mass and charge transfer at low temperatures.

[0071] According to certain preferred embodiments of the present invention, in step (4), the surface of the graphene contains one or more of hydroxyl, carboxyl, and amino groups. Functionalized modified graphene possesses excellent water solubility and interfacial bonding ability. The surface polar functional groups can form hydrogen bonds with polyethyleneimine, alloy powder, and metal oxides, significantly improving the interfacial bonding force of each component, preventing the conductive components from falling off or peeling off during charging and discharging, and simultaneously improving the uniform dispersion of graphene in aqueous dispersions.

[0072] According to certain preferred embodiments of the present invention, in step (4), the second solvent is deionized water.

[0073] According to certain preferred embodiments of the present invention, in step (4), the total weight of cerium oxide, lanthanum oxide, niobium pentoxide, graphene, and conductive carbon black in the additive dispersion accounts for 3-10% by weight. This solid content range ensures that various functional additives are fully dispersed, providing sufficient low-temperature catalytic sites and conductive pathways, while avoiding excessive accumulation of additives that clogs electrode pores, ensuring rapid wetting and ion transport of the electrolyte, and balancing the electrode's catalytic performance, conductivity, and mass transfer performance.

[0074] According to certain preferred embodiments of the present invention, in step (4), the power of the ultrasonic dispersion is 200-500W, the frequency is 30-60 kHz, and the time is 15-45 minutes.

[0075] According to certain preferred embodiments of the present invention, in step (6), the solid content of the aqueous dispersion of the polytetrafluoroethylene binder is 30-50% by weight. This solid content of PTFE aqueous dispersion possesses excellent bonding properties and fluidity, allowing it to uniformly coat the surface of the composite powder, forming a flexible and dense bonding network that firmly binds all powder components together. Simultaneously, it does not clog electrode pores, ensuring good permeability and electrolyte wettability of the electrode, thus meeting the requirements of slurry coating processes.

[0076] According to certain preferred embodiments of the present invention, in step (6), the stirring and mixing time is 1-2 hours.

[0077] According to certain preferred embodiments of the present invention, in step (7), the current collector is a nickel foam current collector. According to certain preferred embodiments of the present invention, the thickness of the nickel foam current collector is in the range of 1-2 mm, and the porosity is 80-95%.

[0078] According to certain preferred embodiments of the present invention, in step (7), the coating thickness of the negative electrode slurry is in the range of 0.5-1.0 mm.

[0079] According to certain preferred embodiments of the present invention, in step (7), the drying includes drying under vacuum at a temperature of 60-80°C for 8-12 hours. The low-temperature vacuum drying process can gently remove moisture and residual solvents from the slurry, avoiding problems such as powder oxidation, thermal damage to the polymer coating layer, and electrode cracking and deformation caused by high-temperature drying.

[0080] According to certain preferred embodiments of the present invention, in step (7), the pressure of the compression molding is 5-15 MPa.

[0081] According to certain preferred embodiments of the present invention, in step (8), the vacuum drying temperature is 120-150°C and the time is 2-4 hours.

[0082] According to certain preferred embodiments of the present invention, based on 100% of the total weight of the negative electrode hydrogen storage material excluding the current collector, the amounts of each component are as follows: 60-75 wt% rare earth-based AB5 type hydrogen storage alloy powder; 15-20 wt% amorphous FeTi-based alloy powder; 2-6 wt% carbon nanotubes; 1-3 wt% polyethyleneimine; 1.5-5 wt% the sum of cerium oxide, lanthanum oxide, and niobium pentoxide; 0.5-2 wt% graphene; 1-3 wt% conductive carbon black; and 2-5 wt% polytetrafluoroethylene binder. Through extensive orthogonal experiments and performance verification, the present invention has determined the optimal dosage range for each component. The dosages of each component are mutually compatible and synergistically enhance each other, taking into account the material's hydrogen storage capacity, conductivity, low-temperature catalytic activity, and structural stability. Rare earth-based AB5 hydrogen storage alloy powder, comprising 60-75% by weight, serves as the main hydrogen storage matrix. This ensures sufficient room-temperature hydrogen storage capacity and basic electrochemical performance. Too low a proportion leads to insufficient overall hydrogen storage capacity, while too high a proportion compresses the space for modification component ratios, significantly weakening the low-temperature modification effect. Amorphous FeTi-based alloy powder, comprising 15-20% by weight, maximizes the optimization of low-temperature hydrogen diffusion channels without significantly sacrificing room-temperature capacity. Too low a proportion limits the low-temperature modification effect, while too high a proportion reduces the overall structural stability of the electrode and exacerbates powder shedding during cycling. A multidimensional carbon-based conductive system composed of carbon nanotubes, graphene, and conductive carbon black constructs a continuous, interconnected three-dimensional conductive network, compensating for the decline in electron conduction rate at low temperatures. The complementary particle size and morphology of different carbon materials effectively fill the powder gaps, reducing the electrode interface impedance. Polyethyleneimine and polytetrafluoroethylene serve as the inner coating modifier and outer binder, respectively, forming a double-layer protective structure that effectively blocks alkaline electrolyte corrosion, inhibits alloy pulverization, and improves cycle life. The precise dosage range of the ternary oxide catalytic components ensures sufficient catalytic active sites while avoiding excessive oxide accumulation that could reduce electrode porosity and hinder mass transfer.

[0083] According to another aspect of the present invention, a negative electrode hydrogen storage material is provided, which is prepared by the preparation method described above. The negative electrode hydrogen storage material prepared by the present invention forms an integrated composite structure of "dual alloy hydrogen storage matrix + multi-element low-temperature catalytic system + multi-dimensional conductive network + multi-layer anti-corrosion coating", which breaks through the limitations of traditional single modification technology.

[0084] According to certain preferred embodiments of the present invention, the negative electrode hydrogen storage material comprises: a current collector; and a hydrogen storage material on the current collector, the hydrogen storage material comprising, based on its total weight of 100%,: 60-75 wt% rare earth-based AB5 type hydrogen storage alloy powder; 15-20 wt% amorphous FeTi-based alloy powder; 2-6 wt% carbon nanotubes; 1-3 wt% polyethyleneimine; 1.5-5 wt% a sum of cerium oxide, lanthanum oxide, and niobium pentoxide; 0.5-2 wt% graphene; 1-3 wt% conductive carbon black; and 2-5 wt% polytetrafluoroethylene binder.

[0085] According to another aspect of the present invention, a nickel-metal hydride battery is provided, the nickel-metal hydride battery comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode comprises the aforementioned negative electrode hydrogen storage material. The present invention is based on a self-developed high-performance low-temperature hydrogen storage negative electrode material, with optimized overall battery system, adapting to the electrochemical characteristics of the negative electrode material, maximizing the advantages of the negative electrode material in wide temperature range, long-lasting performance, and high activity, and preparing a high-performance nickel-metal hydride battery capable of operating in an ultra-wide temperature range of -60℃ to 60℃, thus solving the industry pain points of traditional nickel-metal hydride batteries such as rapid capacity drop, severe polarization, and short lifespan under ultra-low temperature conditions.

[0086] According to certain preferred embodiments of the present invention, the positive electrode is a cobalt-coated spherical nickel hydroxide positive electrode. Cobalt-coated spherical nickel hydroxide positive electrodes are commercially available and possess advantages such as high specific capacity, excellent conductivity, good cycle stability, and good interfacial compatibility. They have a high electrochemical matching degree with the modified negative electrode material of the present invention, and can synergistically reduce the overall internal resistance of the battery, improve the battery's charge-discharge efficiency and wide-temperature stability, and avoid the overall performance degradation problem caused by the mismatch between the positive and negative electrode performances.

[0087] According to certain preferred embodiments of the present invention, the separator is a sulfonated polypropylene separator. The sulfonated polypropylene separator possesses excellent electrolyte wettability, ion conductivity, and resistance to alkali corrosion. It has uniform pores and good barrier properties, effectively preventing short circuits between the positive and negative electrodes of the battery while ensuring rapid ion transport. It meets the ion mass transfer requirements under ultra-low temperature conditions, improving the battery's low-temperature discharge stability and cycle safety.

[0088] According to certain preferred embodiments of the present invention, the electrolyte is a mixed alkaline solution containing KOH, NaOH, and LiOH, wherein the concentration of KOH is 5.0-7.0 mol / L, the concentration of NaOH is 0.5-1.5 mol / L, and the concentration of LiOH is 0.5-1.5 mol / L. This multi-component mixed alkaline electrolyte can optimize the electrolyte's ion concentration, viscosity, and low-temperature fluidity. KOH provides sufficient hydroxide ions to the main electrolyte, ensuring the efficiency of electrochemical reactions under normal operating conditions; NaOH can improve the electrolyte's low-temperature fluidity, reduce low-temperature viscosity, and decrease ion transport resistance; LiOH can modify the electrode interface, inhibit alloy corrosion and pulverization, and improve the electrode's cycle stability.

[0089] The present invention will now be described in more detail with reference to embodiments. It should be noted that these descriptions and embodiments are intended to facilitate understanding of the present invention and are not intended to limit the invention.

[0090] Example In this invention, unless otherwise specified, all reagents used are commercially available products and are used directly without further purification. Furthermore, "%" refers to "weight %" and "parts" refers to "parts by weight".

[0091] Table 1 below lists specific information about the raw materials used in the preparation examples, embodiments, and comparative examples of the present invention.

[0092]

[0093] Table 2 below lists specific information about the experimental equipment used in the embodiments and comparative examples of the present invention.

[0094]

[0095] Performance testing methods (1) Method for testing discharge capacity at room temperature / ultra-low temperature This test references the national standard XB / T 702-2022 "Test of Electrochemical Performance of Rare Earth Hydrogen Storage Alloy Powder for Metal Hydride-Nickel Battery Anode - Three-Electrode System Test Method", and uses the constant current charge-discharge method to test the specific capacity of the sample at room temperature and ultra-low temperature discharge.

[0096] First, assemble the simulated battery for testing using the following steps: 1. Electrode pretreatment: The negative electrode sheets prepared in the following examples and comparative examples were cut into 1 cm × 1 cm square electrodes and vacuum dried at 120 °C for 2 h; the commercial cobalt-coated spherical nickel hydroxide positive electrode (Jilin Yarong Technology Co., Ltd.) was cut into 1 cm × 1 cm sizes, and the positive-to-negative electrode capacity ratio was controlled at 1.2:1; the sulfonated polypropylene diaphragm was cut into 1.2 cm × 1.2 cm, rinsed with deionized water and dried for later use.

[0097] 2. Electrode assembly: Stack the positive electrode, separator, and negative electrode in that order. The separator should completely cover both electrodes to prevent short circuits. Spot weld nickel conductive tabs to each electrode. The working electrode is the negative electrode to be tested, the counter electrode is the positive electrode with excess nickel hydroxide, and the reference electrode is the Hg / HgO standard electrode.

[0098] 3. Electrolyte preparation and injection: Prepare a mixed alkaline electrolyte (6.0 mol / L KOH + 1.0 mol / L NaOH + 1.0 mol / L LiOH) and let it stand for 24 hours; place the stacked electrodes into a sealed polytetrafluoroethylene electrolytic cell, slowly inject the electrolyte until the electrolyte completely submerges the electrodes, and the electrolyte level is 2 mm above the electrodes. Seal the cell cover to prevent electrolyte evaporation and carbon absorption at low temperatures.

[0099] 4. Static wetting: After assembly, the electrolyte is allowed to fully wet the electrode pores, diaphragm and interior of the hydrogen storage alloy at 25°C for 12 hours.

[0100] 5. Activation pretreatment: After standing, connect the simulated battery to the Blue Electric test system, charge at 25℃ with a constant current of 60mA / g for 7h, stand for 5min, and then discharge to 0.6V with 60mA / g. Repeat 3 times until the discharge capacity is stable to complete the electrode activation.

[0101] In the room temperature capacity test, the test was conducted at 25℃, with constant current charge and discharge at rates of 0.2C, 1C, and 2C, and the stable discharge capacity was recorded. In the ultra-low temperature test, the activated batteries were placed in a high and low temperature constant temperature test chamber, with test temperatures set at -40℃ and -60℃, and kept at the same temperature for 2 hours to ensure uniform overall battery temperature. Constant current discharge was performed at 0.2C at -40℃ and at 0.1C at -60℃, with the cutoff voltage uniformly set to 0.6V, and the stable discharge specific capacity (mAh / g) at each temperature was recorded.

[0102] Each sample group was tested in triplicate, and the average value was taken as the final result. This method is a general standard for capacity testing of nickel-metal hydride battery anode materials. The test data is accurate and has good repeatability, and can objectively reflect the hydrogen storage and discharge capabilities of the material at different temperatures.

[0103] (2) Cycle life (cycle stability or capacity retention) test method This test references the national standard GB / T 22084.2-2024 and XB / T 702-2022 "Test Method of Three-Electrode System for Electrochemical Performance of Rare Earth Hydrogen Storage Alloy Powder for Metal Hydride-Nickel Battery Anode", focusing on testing the battery cycle stability and capacity retention under ultra-low temperature (-40℃) conditions.

[0104] The testing equipment used was the LAND CT2001A battery testing system, and the testing environment was a -40℃ constant temperature sealed cryogenic chamber with a temperature fluctuation of ≤±0.5℃ throughout the test. The choice of -40℃ as the testing temperature was intended to simulate the actual working environment of special equipment in ultra-low temperature conditions, such as polar scientific expeditions, high-altitude communications, and aerospace, thereby accurately evaluating the cycle stability of the negative electrode hydrogen storage material of this invention under harsh temperature conditions.

[0105] The fabrication process of the simulated battery is consistent with that in the "Room Temperature / Ultra-Low Temperature Discharge Capacity Testing Method" section above (electrode pretreatment, electrode assembly, electrolyte preparation and injection, static soaking, and activation pretreatment are all the same). After battery activation, a cycle test is performed at -40℃: constant current charging at 1C for 1.4 hours (ensuring the electrodes reach a fully charged state), followed by static soaking for 3 minutes, and then constant current discharging at 1C to a cutoff voltage of 0.6V (vs. Hg / HgO), completing one cycle. 500 charge-discharge cycles are performed continuously, with the discharge capacity recorded every 50 cycles. The capacity retention rate after different number of cycles is calculated based on the stable discharge capacity of the first cycle (capacity retention rate = capacity after cycle / initial stable capacity × 100%). External moisture and temperature interference are strictly isolated during the test to ensure a constant test environment. Each sample is tested in triplicate, and the average value is taken. A higher capacity retention rate after 500 cycles indicates better cycle stability of the electrode material. This test method accurately simulates the long-term working state of batteries under ultra-low temperature conditions, and can characterize the anti-pulverization, anti-corrosion ability and structural stability of anode materials. It is a standard method for evaluating the service life of hydrogen storage anode materials.

[0106] (3) Exchange current density test method This test was conducted in accordance with the general principles of electrochemical kinetic performance testing in XB / T 702-2022 "Test Method for Electrochemical Performance of Rare Earth-based Hydrogen Storage Alloy Powder for Metal Hydride-Nickel Battery Anode: Three-Electrode System Test Method". The linear polarization method was used to test the exchange current density (i0) of the electrode, accurately characterizing the electrochemical reaction kinetics of the material under ultra-low temperature conditions. Exchange current density is an important kinetic parameter describing the ability of an electrode to gain or lose electrons; a higher value indicates better reversibility of the electrode reaction and less electrochemical polarization.

[0107] The test employed a three-electrode system: the negative electrode prepared in the following examples and comparative examples served as the working electrode, a platinum sheet as the counter electrode, and an Hg / HgO electrode as the reference electrode. The electrolyte was a battery-specific mixed alkaline solution (6.0 mol / L KOH + 1.0 mol / L NaOH + 1.0 mol / L LiOH). Before testing, the battery was kept at -40°C for 30 minutes to ensure the temperature and potential of the electrode system remained stable. -40°C was chosen as the test temperature to simulate the actual working environment of special equipment in ultra-low temperature conditions, such as polar scientific expeditions, high-altitude communications, and aerospace, thereby accurately evaluating the intrinsic electrochemical reactivity of the negative electrode hydrogen storage material of this invention under harsh temperature conditions.

[0108] The battery was adjusted to 50% depth of discharge (DOD) and allowed to stand for 30 min to eliminate residual polarization potential. Linear polarization scanning was performed using a CHI660E electrochemical workstation at a scan rate of 5 mV / min and a scan potential range of open circuit potential (OCP) ± 5 mV. After acquiring the polarization curve data, the polarization curves were fitted according to the Butler-Volmer electrochemical equation, and the exchange current density i0 (unit: mA / g) was calculated. Each sample was scanned three times, and the average value was taken. A higher i0 value indicates higher electrode electrochemical reactivity and better low-temperature kinetic performance. This testing method can distinguish the differences in electrochemical performance of different formulations and process materials, providing a quantitative basis for the advancement of technical solutions.

[0109] Preparation Example 1 (Preparation of Rare Earth-based AB5-type Hydrogen Storage Alloy Powder 1 (hereinafter referred to as (AB5 Alloy 1))) This preparation example follows the general chemical formula La. 0.85 Ce 0.15 Ni 4.2 Co 0.3 Mn 0.3 Al 0.2 Rare earth-based AB5-type hydrogen storage alloy powder was prepared. First, La, Ce, Ni, Co, Mn, and Al metal raw materials were weighed according to stoichiometric ratios. The prepared metal raw materials were placed in a vacuum induction melting furnace, and a vacuum of 1×10⁻⁶ was first applied. -3Below Pa, high-purity argon gas was introduced for protection, and the temperature was raised to 1500 °C for constant-temperature melting for 40 min to completely melt the metal raw materials and form a homogeneous alloy liquid. The high-temperature alloy liquid was then rapidly poured into a water-cooled copper mold, and a dense, homogeneous alloy ingot was obtained through rapid solidification. The ingot was transferred to an argon-protected tubular annealing furnace and annealed at 1000 °C for 15 h to eliminate internal stress and compositional inhomogeneity generated during the melting process. After annealing, the ingot was naturally cooled to room temperature. It was first mechanically crushed into particles, then ball-milled in a planetary ball mill for further refinement. After ball milling, the particles were sieved to obtain AB5 type hydrogen storage alloy powder with a particle size of approximately 35 μm.

[0110] Preparation Example 2 (Preparation of Rare Earth-based AB5-type Hydrogen Storage Alloy Powder 2 (hereinafter referred to as (AB5 Alloy 2))) This preparation example follows the general chemical formula La. 0.65 Ce 0.35 Ni 3.5 Co 0.6 Mn 0.5 Al 0.4 Rare earth-based AB5-type hydrogen storage alloy powder was prepared. First, La, Ce, Ni, Co, Mn, and Al metal raw materials were weighed according to stoichiometric ratios. The prepared metal raw materials were placed in a vacuum induction melting furnace, and a vacuum of 1×10⁻⁶ was first applied. -3 Below Pa, high-purity argon gas was introduced for protection, and the temperature was raised to 1600 °C for constant-temperature melting for 35 min to completely melt the metal raw materials and form a homogeneous alloy liquid. The high-temperature alloy liquid was then rapidly poured into a water-cooled copper mold, and a dense, homogeneous alloy ingot was obtained through rapid solidification. The ingot was transferred to an argon-protected tubular annealing furnace and annealed at 1100 °C for 8 h to eliminate internal stress and compositional inhomogeneity issues generated during the melting process. After annealing, the ingot was naturally cooled to room temperature. It was first mechanically crushed into particles, then ball-milled in a planetary ball mill for further refinement. After ball milling, the particles were sieved to obtain AB5 type hydrogen storage alloy powder with a particle size of approximately 39 μm.

[0111] Preparation Example 3 (Preparation of Amorphous FeTi-based Alloy Powder 1 (hereinafter referred to as FeTi Alloy 1)) This preparation example follows the chemical formula FeTi 1.1 Ni 0.05 Gd 0.05Amorphous FeTi-based alloy powder was prepared. Specifically, Fe, Ti, Ni, and Gd metal raw materials were accurately weighed in an argon-protected glove box and mixed uniformly according to stoichiometric ratio. The mixed raw materials and stainless steel grinding balls were fed into a planetary ball mill at a ball-to-material ratio of 15:1. High-purity argon gas was circulated throughout the process to prevent oxidation. The mill was set to a speed of 400 rpm and continuously milled for 60 h. Through high-energy mechanical alloying, the metal lattice was broken, forming a disordered amorphous structure. After ball milling, the powder was removed and sieved through 400-mesh and 600-mesh standard sieves to remove large particle impurities, finally obtaining amorphous FeTi-based alloy powder with a particle size of approximately 30 μm.

[0112] Preparation Example 4 (Preparation of Amorphous FeTi-based Alloy Powder 2 (FeTi Alloy 2 for short)) This preparation example follows the chemical formula FeTi 1.08 Co 0.1 Gd 0.02 Amorphous FeTi-based alloy powder was prepared. Specifically, Fe, Ti, Co, and Gd metal raw materials were accurately weighed in an argon-protected glove box and mixed uniformly according to stoichiometric ratio. The mixed raw materials and stainless steel grinding balls were fed into a planetary ball mill at a ball-to-material ratio of 25:1. High-purity argon gas was circulated throughout the process to prevent oxidation. The mill was set to a speed of 500 rpm and continuously milled for 40 hours. Through high-energy mechanical alloying, the metal lattice was broken, forming a disordered amorphous structure. After ball milling, the powder was removed and sieved through 400-mesh and 600-mesh standard sieves to remove large particle impurities, finally obtaining amorphous FeTi-based alloy powder with a particle size of approximately 35 μm.

[0113] Preparation Example 5 (Preparation of Modified Multi-walled Carbon Nanotubes) First, multi-walled carbon nanotubes were calcined at 450℃ under an argon atmosphere for 3 h. A mixed acid solution of concentrated sulfuric acid and concentrated nitric acid (volume ratio 3:1) was prepared, and the calcined carbon nanotubes were immersed in the acid solution and refluxed at 70℃ for 8 h to etch and activate the tube walls, introducing oxygen-containing functional groups. After acid treatment, the powder was repeatedly washed with deionized water until the washing solution was neutral, and then vacuum dried at 90℃ for 16 h to remove residual acid and moisture. Next, the dried powder was placed in a low-temperature plasma treatment instrument and treated for 30 min at a power of 150 W and an oxygen flow rate of 80 mL / min to further activate the active sites on the tube walls. Subsequently, a mixed aqueous solution containing 1.0 mol / L Ni(NO3)2 and 0.2 mol / L Co(NO3)2 was prepared, and the activated carbon nanotubes were immersed in it and sonicated at room temperature for 3 h. Finally, the loaded powder was placed in a tube furnace and reduced at 450℃ under a hydrogen atmosphere for 3 h to obtain modified multi-walled carbon nanotubes.

[0114] Example 1 Example 1 uses AB5 type rare earth alloy powder 1 from Preparation Example 1, amorphous FeTi-based alloy powder 1 from Preparation Example 3, and modified carbon nanotubes from Preparation Example 5.

[0115] The raw material proportions by weight are as follows: 60% by weight of rare earth-based AB5 hydrogen storage alloy powder, 20% by weight of amorphous FeTi-based alloy powder, 5% by weight of modified carbon nanotubes, 2% by weight of polyethyleneimine, 5% by weight of total (cerium oxide + lanthanum oxide + niobium pentoxide), 2% by weight of graphene, 2% by weight of conductive carbon black, and 4% by weight of polytetrafluoroethylene binder.

[0116] First, composite alloy powder was prepared. Rare earth-based AB5 hydrogen storage alloy powder 1 and amorphous FeTi-based alloy powder 1 were placed in an argon-protected ball mill and mixed at a ball-to-powder ratio of 20:1 and a speed of 300 rpm for 4 hours to obtain uniform composite alloy powder. Then, a carbon nanotube-polyethyleneimine dispersion was prepared. The modified carbon nanotubes from Preparation Example 5 were dispersed in deionized water, and polyethyleneimine was added. The mixture was ultrasonically dispersed at 300 W and 50 kHz for 45 min to obtain a stable dispersion with a solid content of 12%. The composite alloy powder was added to the dispersion and stirred at a constant temperature for 40 min to obtain the first mixture. Next, an additive dispersion was prepared. Cerium oxide, lanthanum oxide, and niobium pentoxide were selected and mixed at a weight ratio of 1:3 (cerium oxide: lanthanum oxide) and 1:2 (cerium oxide: niobium pentoxide). Graphene and conductive carbon black were added to deionized water and ultrasonically dispersed at 400 W for 30 min to obtain a uniform additive dispersion. The additive dispersion was slowly added dropwise to the first mixture and stirred for 30 min to obtain the second mixture. A PTFE aqueous dispersion with a solid content of 40% was added to the second mixture, and the mixture was stirred at a constant temperature for 1.5 h to prepare a uniform negative electrode slurry. The slurry was uniformly coated onto a nickel foam current collector with a coating thickness of 0.8 mm, vacuum dried at 70℃ for 10 h, and then pressed into a negative electrode sheet under a pressure of 10 MPa. Finally, the negative electrode sheet was placed in a vacuum drying oven at 135℃ for 3 h to completely remove residual moisture and solvent, thus obtaining the negative electrode hydrogen storage material 1.

[0117] Examples 2-12 and Comparative Examples 1-6 Examples 2-12 and Comparative Examples 1-6 were prepared in a manner similar to that of Example 1 to prepare negative electrode hydrogen storage materials 2-12 and comparative negative electrode hydrogen storage materials 1-6, the only difference being that the component types and ratios were changed as shown in Table 3 below.

[0118] The only difference between Comparative Example 1 and Example 1 is that Comparative Example 1 did not add amorphous FeTi-based alloy powder, but instead used an equal amount of rare earth-based AB5-type hydrogen storage alloy powder. The only difference between Comparative Example 2 and Example 1 is that Comparative Example 2 did not add rare earth-based AB5-type hydrogen storage alloy powder, but instead used an equal amount of amorphous FeTi-based alloy powder. The only difference between Comparative Example 3 and Example 1 is that Comparative Example 3 did not add cerium oxide, but instead used an equal amount of lanthanum oxide. The only difference between Comparative Example 4 and Example 1 is that Comparative Example 4 did not add lanthanum oxide, but instead used an equal amount of cerium oxide. The only difference between Comparative Example 5 and Example 1 is that Comparative Example 5 did not add niobium pentoxide, but instead used an equal amount of cerium oxide.

[0119] Based on the room temperature / ultra-low temperature discharge capacity test method, cycle life test method, and exchange current density test method described in detail above, the negative electrode hydrogen storage materials 2-12 and comparative negative electrode hydrogen storage materials 1-6 prepared in Examples 1-12 and Comparative Examples 1-6 above were tested, and the results are shown in Table 4 below.

[0120]

[0121]

[0122] As can be seen from the performance test results of Examples 1-12 and Comparative Examples 1-6 in Table 4, the present invention can simultaneously improve room temperature capacity, ultra-low temperature discharge performance, electrochemical reaction kinetics and long-cycle stability by combining rare earth AB5 type hydrogen storage alloy powder with amorphous FeTi-based alloy powder, synergistic modification with ternary rare earth oxide catalyst, and multi-scale conductive network composite coating.

[0123] First, we compare Comparative Example 1 and Comparative Example 2, which use a single alloy system, with all examples. Comparative Example 1 uses only rare-earth-based AB5-type hydrogen storage alloy powder and completely omits amorphous FeTi-based alloy powder. Its capacity at 25°C is only 318.6 mAh / g, its capacity at -40°C drops significantly to 196.2 mAh / g, its capacity at -60°C is only 112.5 mAh / g, its exchange current density at -40°C is only 18.3 mA / g, and its capacity retention rate after 500 cycles is only 64.2%. Comparative Example 2 uses only amorphous FeTi-based alloy powder and does not use rare-earth-based AB5-type hydrogen storage alloy powder. Its capacity at room temperature further drops to 302.5 mAh / g. Although its low-temperature performance is better than Comparative Example 1, it is far inferior to any of the examples. All embodiments rely on a dual-alloy synergistic system, with the capacity remaining stable at 332.6-342.1 mAh / g at room temperature, reaching 268.3-288.5 mAh / g at -40℃, and still maintaining 178.5-198.2 mAh / g at -60℃. The exchange current density and cycle capacity retention rate are significantly improved simultaneously, proving that rare earth-based AB5-type hydrogen storage alloy powder provides the basic hydrogen storage capacity, while the disordered structure of amorphous FeTi-based alloy powder broadens the low-temperature hydrogen diffusion channels. The combination of the two has an unexpected synergistic gain.

[0124] Next, the comparative groups with missing oxide components in the three-way catalytic converter were analyzed. Comparative Example 3 (removing CeO2), Comparative Example 4 (removing La2O3), and Comparative Example 5 (removing Nb2O5) all showed a significant decline in electrochemical performance. The capacity range at -40℃ was only 229.8-242.5 mAh / g, the exchange current density was 20.8-22.1 mA / g, and the highest retention rate after 500 cycles was only 72.3%. Although Comparative Example 6 retained all three oxides, the imbalance in the ratio of CeO2 to La2O3 and Nb2O5 resulted in a significant difference in low-temperature performance and cycle stability compared to the examples. This indicates that CeO2, La2O3, and Nb2O5 form a synergistic low-temperature catalytic system. CeO2 regulates interfacial oxygen vacancies to lower the activation energy, La2O3 optimizes hydrogen adsorption sites, and Nb2O5 accelerates the bulk diffusion of hydrogen atoms. The absence of any component or deviation in the ratio will destroy the synergistic catalytic effect, making it impossible to achieve the optimized kinetics at ultra-low temperatures.

[0125] Further comparisons were made between Examples 1-9 and Examples 10-12 with preferred formulations. Examples 10-12 achieved peak performance across the entire experimental group. Specifically, Example 11 exhibited the following optimal performance: room temperature capacity 342.1 mAh / g, -40℃ capacity 288.5 mAh / g, -60℃ capacity 198.2 mAh / g, exchange current density 31.8 mA / g, and capacity retention of 87.1% after 500 cycles, representing the best performance among all samples.

[0126] Obviously, those skilled in the art can make various modifications and variations to this disclosure without departing from the spirit and scope of this disclosure. Therefore, if such modifications and variations fall within the scope of this invention, this disclosure is also intended to include such modifications and variations.

Claims

1. A method for preparing a negative electrode hydrogen storage material, characterized in that, The preparation method includes the following steps: (1) Mix rare earth-based AB5 type hydrogen storage alloy powder and amorphous FeTi-based alloy powder to obtain composite alloy powder; (2) Disperse carbon nanotubes in a first solvent, then add polyethyleneimine and perform ultrasonic dispersion to obtain a carbon nanotube-polyethyleneimine dispersion. (3) Add the composite alloy powder obtained in step (1) to the carbon nanotube-polyethyleneimine dispersion obtained in step (2), stir and mix to obtain the first mixture; (4) Add cerium oxide, lanthanum oxide, niobium pentoxide, graphene and conductive carbon black to the second solvent and disperse them by ultrasonication to obtain an additive dispersion, wherein the weight ratio of cerium oxide to lanthanum oxide is in the range of 1:3-1:8 and the weight ratio of cerium oxide to niobium pentoxide is in the range of 1:2-1:

5. (5) Add the additive dispersion obtained in step (4) to the first mixture obtained in step (3), stir and mix to obtain the second mixture; (6) Prepare a water dispersion of polytetrafluoroethylene binder, add it to the second mixture obtained in step (5), stir and mix to obtain a negative electrode slurry; (7) Coat the negative electrode slurry obtained in step (6) onto the current collector, dry it and press it into shape to obtain a negative electrode sheet; (8) The negative electrode sheet obtained in step (7) is vacuum dried to obtain the negative electrode hydrogen storage material.

2. The method for preparing the negative electrode hydrogen storage material according to claim 1, characterized in that, The weight ratio of cerium oxide to lanthanum oxide is in the range of 1:4 to 1:6, and the weight ratio of cerium oxide to niobium pentoxide is in the range of 1:3 to 1:

4.

3. The method for preparing the negative electrode hydrogen storage material according to claim 1, characterized in that, Based on the total weight of the remaining portion of the negative electrode hydrogen storage material excluding the current collector being 100%, the amounts of each component are as follows: 60-75% by weight of rare earth-based AB5 type hydrogen storage alloy powder; 15-20% by weight of amorphous FeTi-based alloy powder; 2-6% by weight of carbon nanotubes; 1-3% by weight of polyethyleneimine; The sum of 1.5-5% by weight of cerium oxide, lanthanum oxide and niobium pentoxide; 0.5-2% by weight of graphene; 1-3% by weight of conductive carbon black; 2-5% by weight of polytetrafluoroethylene adhesive.

4. The method for preparing the negative electrode hydrogen storage material according to claim 1, characterized in that, The general chemical formula of the rare earth-based AB5 type hydrogen storage alloy powder is La. 1-x Ce x Ni 5-y-z-w Co y Mn z Al w Where: x ranges from 0.15 to 0.35; y ranges from 0.3 to 0.6; z ranges from 0.3 to 0.5; and w ranges from 0.2 to 0.

4.

5. The method for preparing the negative electrode hydrogen storage material according to claim 1, characterized in that, The chemical formula of the amorphous FeTi-based alloy powder is FeTi. 1.2-a-b M a N b Where: M is a transition metal element Co and / or Ni; N is a rare earth element Y and / or Gd; the value of a ranges from 0.05 to 0.15; and the value of b ranges from 0.02 to 0.

08.

6. The method for preparing the negative electrode hydrogen storage material according to claim 1, characterized in that, The carbon nanotubes are modified multi-walled carbon nanotubes; The weight-average molecular weight of the polyethyleneimine is 600-25000; The first solvent is deionized water; or In the carbon nanotube-polyethyleneimine dispersion, the total weight of carbon nanotubes and polyethyleneimine accounts for 6-17% by weight.

7. The method for preparing the negative electrode hydrogen storage material according to claim 1, characterized in that, The second solvent is deionized water; In the additive dispersion, the total weight of cerium oxide, lanthanum oxide, niobium pentoxide, graphene, and conductive carbon black is 3-10% by weight; or The solid content of the aqueous dispersion of the polytetrafluoroethylene adhesive is 30-50% by weight.

8. The method for preparing the negative electrode hydrogen storage material according to claim 1, characterized in that, The current collector is a nickel foam current collector; or The coating thickness of the negative electrode slurry is in the range of 0.5-1.0 mm.

9. A negative electrode hydrogen storage material, characterized in that, The negative electrode hydrogen storage material is prepared by the preparation method according to any one of claims 1-8.

10. A nickel-metal hydride battery, characterized in that, The nickel-metal hydride battery includes a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode comprises the negative electrode hydrogen storage material as described in claim 9.

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