Nickel-hydrogen battery and preparation method thereof

Abstract

The present invention relates to a nickel-hydrogen battery, comprising a positive electrode, a negative electrode, a diaphragm and an electrolyte, wherein the positive electrode comprises a positive electrode active material, a positive electrode additive and a positive electrode conductive agent, wherein the positive electrode active material is a spherical nickel hydroxide coated with β-CoOOH, the positive electrode additive contains tungsten, zinc, yttrium and ytterbium, and the positive electrode conductive agent comprises graphene; the negative electrode comprises a negative electrode active material, a negative electrode additive and a negative electrode conductive agent, wherein the negative electrode active material is an A2B7 type hydrogen storage alloy, and the B position of the A2B7 type crystal structure does not contain cobalt, manganese, nickel and aluminum, the negative electrode additive comprises yttrium oxide, and the negative electrode conductive agent comprises carbon nanotubes; the electrolyte of the nickel-hydrogen battery is an alkaline aqueous solution configured with an alkali metal hydroxide; and the diaphragm adopts a polypropylene diaphragm paper treated with grafting or fluorination or sulfonation. The present invention also relates to a preparation method of the above nickel-hydrogen battery.

Description

Technical Field

[0001] The present invention relates to the field of secondary batteries, and in particular to a nickel-hydrogen battery and a preparation method thereof. Background Art

[0002] The nickel-hydrogen battery using hydrogen storage alloy as the negative electrode active material not only has excellent power characteristics, but also has high durability (life characteristics and storage characteristics). However, the change of ambient temperature has a huge impact on the performance of nickel-hydrogen batteries. When the ambient temperature exceeds 30°C, the charging efficiency of existing nickel-hydrogen batteries will decrease as the temperature rises. When the ambient temperature exceeds 40°C, the charging and discharging efficiency, power retention and cycle life of nickel-hydrogen batteries will all decay rapidly. Therefore, it is expected to further improve the performance of nickel-hydrogen batteries in high temperature environments. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention provides a nickel-hydrogen battery, which still has relatively excellent charging efficiency, power retention and cycle life in a high temperature environment. The charging efficiency of the nickel-hydrogen battery at an ambient temperature of 50°C is not less than 90% of the nominal capacity (NC) of the nickel-hydrogen battery, the power retention of the nickel-hydrogen battery at an ambient temperature of 50°C is improved by no less than 30% compared with the power retention of the existing nickel-hydrogen battery with the same nominal capacity at an ambient temperature of 50°C, and the cycle life of the nickel-hydrogen battery at an ambient temperature of 50°C is improved by no less than 40% compared with the cycle life of the existing nickel-hydrogen battery with the same nominal capacity at an ambient temperature of 50°C.

[0004] The nickel-hydrogen battery provided by the present invention comprises a positive electrode, a negative electrode containing the hydrogen storage alloy, a separator and an electrolyte arranged therebetween, and the nickel-hydrogen battery simultaneously satisfies:

[0005] 1. The positive electrode active material of the positive electrode of the nickel-hydrogen battery uses spherical nickel hydroxide coated with β-CoOOH. The spherical nickel hydroxide is coated with β-CoOOH by chemical vapor deposition process, so the coating layer is more stable and dense, so that the nickel-hydrogen battery is not easily reduced or dissolved at high temperature in a high temperature environment;

[0006] 2. The positive electrode additive used in the positive electrode of the nickel-hydrogen battery contains tungsten (W), zinc (Zn), yttrium (Y) and ytterbium (Yb). The effect of the Zn element is that it can effectively reduce the expansion of the spherical nickel hydroxide during the floating charge of the nickel-hydrogen battery in a high temperature environment, thereby avoiding the damage of the coating layer of the spherical nickel hydroxide during the floating charge; the W element of the positive electrode additive can slowly dissolve into Na2WO4 in a strong alkaline environment, and the dissolved Na2WO4 surrounds the spherical nickel hydroxide, which can effectively improve the oxygen evolution potential of the positive electrode; Y and Yb can effectively improve the oxygen evolution potential of the positive electrode of the spherical nickel hydroxide during the floating charge in a high temperature environment, avoiding the consumption of water in the electrolyte and the oxidation of hydrogen storage alloys by the oxygen generated during the floating charge due to the oxygen evolution of the positive electrode; the W element, Y and Yb elements can produce a synergistic effect to significantly improve the oxygen evolution potential of the positive electrode, and the synergistic effect can increase the oxygen evolution potential of the positive electrode to avoid the increase in the internal pressure of the nickel-hydrogen battery caused by the inability of the oxygen generated during the floating charge to be quickly compounded by the negative electrode, thereby effectively avoiding the leakage of the electrolyte of the nickel-hydrogen battery;

[0007] 3. The diaphragm of the nickel-hydrogen battery adopts a polypropylene diaphragm paper that has been grafted, fluorinated or sulfonated. The fluorinated or grafted polypropylene diaphragm paper can be kept in a high temperature environment for a long time without becoming brittle, and the grafted or fluorinated polypropylene diaphragm paper will not reduce the hardness of the polypropylene fiber. Therefore, the pressure resistance of the diaphragm remains unchanged, and when the positive and negative electrodes of the nickel-hydrogen battery expand, the diaphragm will not undergo obvious compression deformation, thereby avoiding the increase in the internal resistance of the nickel-hydrogen battery caused by the reduction of the electrolyte in the diaphragm;

[0008] 4. The electrolyte of the nickel-hydrogen battery is an alkaline aqueous solution prepared by using alkali metal hydroxide, the alkali metal hydroxide includes potassium hydroxide, sodium hydroxide, lithium hydroxide, and the concentration of the alkali metal hydroxide is 5.5-9.0 mol / L;

[0009] 5. The negative electrode active material used in the negative electrode of the nickel-hydrogen battery comprises a hydrogen storage alloy, and the hydrogen storage alloy adopts an alloy with an A2B7 type crystal structure, and the B position of the A2B7 type crystal structure does not contain elements such as cobalt (Co), manganese (Mn), nickel (Ni) and aluminum (Al). The reason is that if the dissolution of Co, Mn, Ni and Al in the hydrogen storage alloy into the electrolyte increases significantly under high temperature environment, the high temperature life characteristics of the nickel-hydrogen battery will be reduced, and the Co, Mn, Ni and Al in the hydrogen storage alloy are easily dissolved into the electrolyte in a strong alkaline environment, resulting in an increase in the self-discharge of the nickel-hydrogen battery;

[0010] 6. The negative electrode additive used in the negative electrode of the nickel-hydrogen battery includes Y2O3. After Y2O3 is dissolved in a strong alkali, it will form a protective film on the negative electrode, effectively alleviating the corrosion of the hydrogen storage alloy in a strong alkali environment;

[0011] 7. The negative electrode conductive agent used in the negative electrode of the nickel-hydrogen battery includes carbon nanotubes. The conductive method of the carbon nanotubes is line-point conductivity, which is better than the point-to-point conductivity of carbon black, graphite, etc., and can effectively reduce the resistance of the nickel-hydrogen battery. At the same time, the hollow tube of the carbon nanotube can store and stabilize hydrogen molecules. When the nickel-hydrogen battery is charged, the hydrogen storage alloy will increase significantly with the increase of hydrogen absorption. The PCT platform, at this time, the absorbed hydrogen is unstable, and the unstable hydrogen can be absorbed by the carbon nanotubes, which is equivalent to increasing the capacity of the negative electrode and improving the cycle life of the nickel-hydrogen battery. During the charge and discharge cycle of the nickel-hydrogen battery, oxygen evolution will inevitably occur at the positive electrode of the nickel-hydrogen battery. The evolved oxygen can be effectively compounded by the hydrogen molecules in the carbon nanotubes, thereby reducing the internal pressure of the nickel-hydrogen battery and preventing the generated oxygen from oxidizing the hydrogen storage alloy. At the same time, it can avoid the leakage of the exhaust valve caused by excessive internal pressure of the nickel-hydrogen battery, thereby improving the cycle life of the nickel-hydrogen battery;

[0012] 8. The positive electrode conductive agent used in the positive electrode of the nickel-hydrogen battery includes two-dimensional nanostructured graphene to form a three-dimensional conductive network on the surface of the positive electrode, thereby improving the charging acceptance capacity of the positive electrode active material under high temperature environment to improve the oxygen evolution overpotential of the nickel-hydrogen battery, and improve the charging and discharging efficiency of the nickel-hydrogen battery under large current, thereby reducing the thermal effect caused by oxygen generation and recombination in the system, reducing the internal resistance of the nickel-hydrogen battery, reducing electrochemical polarization, concentration polarization and ohmic polarization, reducing the generation of corresponding heat, and greatly improving the high temperature performance of the nickel-hydrogen battery.

[0013] Among them, W in the positive electrode additive comes from W oxide or a salt containing W element, Zn in the positive electrode additive comes from Zn oxide or a salt containing Zn element, Y in the positive electrode additive comes from Y oxide or a salt containing Y element, and Yb in the positive electrode additive comes from Yb oxide or a salt containing Yb element.

[0014] In one embodiment, W in the positive electrode additive is derived from WO3, Zn in the positive electrode additive is derived from ZnO, Y in the positive electrode additive is derived from Y2O3, and Yb in the positive electrode additive is derived from Yb2O3.

[0015] Compared with the prior art, the nickel-hydrogen battery provided by the present invention has at least the following beneficial effects:

[0016] 1. The positive electrode uses positive electrode additives containing W, Zn, Y, and Yb to effectively increase the oxygen evolution potential of the positive electrode under high temperature conditions and reduce the expansion of the spherical nickel hydroxide of the positive electrode;

[0017] 2. The diaphragm is grafted or fluorinated, which will not reduce the hardness of the diaphragm paper and ensure its pressure resistance. When the positive and negative electrodes expand, the diaphragm paper will not be significantly compressed, which will reduce the electrolyte in the diaphragm paper and increase the internal resistance of the battery.

[0018] 3. The negative electrode uses A2B7 type hydrogen storage alloy to improve the battery's power retention in high temperature environments;

[0019] 4. The negative electrode additives used in the negative electrode include Y2O3, which can effectively form a protective film to alleviate the corrosion of the hydrogen storage alloy in a strong alkaline environment;

[0020] 5. The negative electrode conductive agent used in the negative electrode includes carbon nanotubes, which can effectively reduce the internal resistance of the battery and increase the capacity of the negative electrode. The oxygen generated by the positive electrode during the composite cycle process can increase the battery cycle life.

[0021] On the other hand, the present invention also provides a method for preparing the above-mentioned nickel-hydrogen battery, comprising the following steps:

[0022] Step 1, preparation of positive electrode: take binder and pure water, glue at a speed of 150-300r / min for 2-6h, then add positive electrode active material, positive electrode additive and positive electrode conductive agent, stir at a speed of 100-300r / min for 3-5h to obtain positive electrode slurry. Apply the prepared positive electrode slurry on the positive electrode skeleton with a coating thickness of 1.0-2.0mm. After coating, place it in an oven at 80-150℃ for 0.5-1h to dry the positive electrode slurry to obtain a positive electrode substrate, and finally cut it into strips, cut it into pieces, and spot weld the pole ears to obtain the positive electrode;

[0023] Step 2, preparation of negative electrode: negative electrode active material, negative electrode additive, binder, negative electrode conductive agent and appropriate amount of water are mixed to obtain a mixture slurry. The mixture slurry is coated on both sides of a core material made of iron punching metal that has been nickel-plated, with a coating thickness of 0.5-1.0mm. The mixture slurry is dried, and rolled together with the core material by a roller at room temperature with a pressure of 1500-3000MPa, and the obtained plate is cut to obtain a negative electrode;

[0024] Step 3, preparation of nickel-hydrogen battery: take the positive electrode obtained in step 1 and the negative electrode obtained in step 2, wind them into a battery core with a diaphragm, install them into a nickel-plated steel shell, weld the cap, inject the electrolyte, and seal to obtain a nickel-hydrogen battery.

[0025] The positive electrode conductive agent contains graphene slurry, and the negative electrode conductive agent contains carbon nanotubes. The preparation method of the graphene slurry is as follows: take 1-5 parts of adhesive and 20-40 parts of pure water, and mix them at a speed of 150-300r / min for 2-6h; add 40-60 parts of graphene and 1-4 parts of graphene dispersion, stir at a speed of 100-300r / min for 20-60min, put into a ball mill and use a ball mill to disperse by ball milling until the viscosity is 3000-4000cP, and then add 1-6 parts of pure water to adjust the viscosity to 1000-2100cP to obtain graphene slurry.

[0026] Wherein, the adhesive is one or a mixture of several substances selected from sodium carboxymethyl cellulose, hydroxypropyl methyl cellulose, styrene-butadiene rubber or polytetrafluoroethylene.

[0027] Wherein, the positive electrode skeleton is one of foamed nickel and nickel-plated perforated steel strip.

[0028] The positive electrode conductive agent also contains one or a mixture of several substances selected from the group consisting of activated carbon, carbon black, acetylene carbon black, super carbon black Super-P, graphite, polyaniline or polyacetylene. The negative electrode conductive agent also contains one or a mixture of several substances selected from the group consisting of activated carbon, carbon black, acetylene carbon black, super carbon black Super-P, graphite, polyaniline or polyacetylene.

[0029] Wherein, the diaphragm is a polypropylene diaphragm paper that is grafted or fluorinated or sulfonated; and the electrolyte is a ternary electrolyte of sodium hydroxide, potassium hydroxide and lithium hydroxide.

[0030] In one embodiment, the AA-type 2500mAh nickel-hydrogen battery prepared by the preparation method provided by the present invention can effectively improve the charging oxygen evolution potential of the nickel-hydrogen battery in a high temperature environment, and improve the charging efficiency of the nickel-hydrogen battery in a high temperature environment, for example, the charging efficiency at 50°C is not less than 90% of the nominal capacity (NC). Compared with the existing AA-type 2500mAh nickel-hydrogen battery, the AA-type 2500mAh nickel-hydrogen battery prepared by the preparation method provided by the present invention can improve the power retention in a high temperature environment by about 30%, and the cycle life of the AA-type 2500mAh nickel-hydrogen battery prepared by the method in a high temperature environment can be improved by 40%.

[0031] In the preparation method provided by the present invention, the positive electrode conductive agent contains graphene slurry, which can significantly enhance the adhesion between the positive electrode active material and the positive electrode skeleton, and the negative electrode conductive agent contains carbon nanotubes, which can significantly enhance the adhesion between the negative electrode active material and the core material. The positive electrode conductive agent contains graphene slurry and the negative electrode conductive agent contains carbon nanotubes, which can significantly reduce the interface resistance, improve the rate performance of the nickel-hydrogen battery, reduce and stabilize the internal resistance of the nickel-hydrogen battery to improve the rate cycle life.

[0032] The following describes the invention in conjunction with specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The accompanying drawings further illustrate the present invention, but the embodiments in the accompanying drawings do not constitute any limitation to the present invention.

[0034] Figure 1 This is a comparison chart of the power retention of NiMH batteries placed at an ambient temperature of 60°C for 35 days;

[0035] Figure 2This is the charging curve of a NiMH battery placed at an ambient temperature of 50°C;

[0036] Figure 3 This is the capacity curve of NiMH battery in 1C / 1C cycle test at room temperature. DETAILED DESCRIPTION

[0037] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0038] The graphene described in the present invention is a carbon material with hexagonal mesh bonding and has many excellent electrical properties. Carbon atoms have four valence electrons, so each carbon atom contributes an unbonded π electron, and these π electrons can form orbits in a direction perpendicular to the plane. The π electrons can move freely in the crystal, giving graphene good conductivity, far exceeding the tolerance of copper to high current density. By adding a small amount of graphene as a conductive agent to the positive and negative electrodes of nickel-hydrogen batteries, not only can the original energy density of nickel-hydrogen batteries be maintained, but the output power density of nickel-hydrogen batteries can also be greatly improved.

[0039] Example 1

[0040] This embodiment provides an AA-size cylindrical nickel-hydrogen battery, and the preparation of the nickel-hydrogen battery includes the following steps:

[0041] Step 1, preparation of positive electrode: take 1-5 parts of adhesive and 30-50 parts of pure water, glue at a speed of 150-300r / min for 2-6h, then add 35-65 parts of positive electrode active material, 1-3 parts of positive electrode additive and 2-5 parts of positive electrode conductive agent, stir at a speed of 100-300r / min for 3-5h to obtain positive electrode slurry. Apply the prepared positive electrode slurry on the positive electrode skeleton with a coating thickness of 1.0-2.0mm. After coating, place it in an oven at 80-150℃ for 0.5-1h to dry the positive electrode slurry to obtain a positive electrode substrate, and finally cut it into strips, cut it into pieces, and spot weld the pole ears to obtain the positive electrode;

[0042] Step 2, preparation of negative electrode: 100-105 parts of negative electrode active material, 2-4 parts of negative electrode additive, 1-3 parts of binder, 1-3 parts of negative electrode conductive agent and appropriate amount of water are mixed to obtain a mixture slurry. The mixture slurry is coated on both sides of a core material made of iron punching metal that has been nickel-plated, with a coating thickness of 0.5-1.0mm. The mixture slurry is dried, and rolled together with the core material by a roller at room temperature with a pressure of 1500-3000MPa, and the obtained plate is cut to obtain a negative electrode;

[0043] Step 3, preparation of nickel-hydrogen battery: take the positive electrode obtained in step 1 and the negative electrode obtained in step 2, wind them into a battery core with a diaphragm, install them into a nickel-plated steel shell, weld the cap, inject the electrolyte, and seal to obtain a nickel-hydrogen battery.

[0044] Among them, the binder includes sodium carboxymethyl cellulose, sodium polyacrylate, and SRB emulsion; the positive electrode active material is spherical nickel hydroxide coated with β-CoOOH; the positive electrode additives include WO3, ZnO, Y2O3 and Yb2O3; the positive electrode conductor includes graphene slurry and graphite; the negative electrode active material is an A2B7 type hydrogen storage alloy containing La, Pr, Nd, Ni, Al, Mg, Sm, Y and Zr; the negative electrode additive includes Y2O3; the negative electrode conductor includes carbon nanotubes and super carbon black Super-P; the diaphragm is sulfonated polypropylene diaphragm paper; and the electrolyte is a ternary electrolyte of sodium hydroxide, potassium hydroxide and lithium hydroxide (the total concentration of sodium hydroxide, potassium hydroxide and lithium hydroxide is 5.5-9.0 mol / L).

[0045] After testing, the AA-type cylindrical nickel-hydrogen battery provided in this embodiment is charged at 1C for 70 minutes at 40°C, and the discharge capacity is 95-97% of the capacity at room temperature. After cycling 350 times at 40°C, the capacity retention rate is 80-85%; the nickel-hydrogen battery is charged at 1C for 70 minutes at 70°C, and the discharge capacity is 82-86% of the capacity at room temperature. After cycling 100 times at 70°C, the capacity retention rate is 80-84%.

[0046] Example 2

[0047] This embodiment provides a AA-size nickel-metal hydride battery with a nominal capacity of 2500 mAh.

[0048] The positive electrode of the nickel-hydrogen battery includes a positive electrode active material and a positive electrode additive. The positive electrode active material uses spherical nickel hydroxide coated with β-CoOOH. The positive electrode additive includes WO3, ZnO, Y2O3 and Yb2O3. Taking the total mass of the positive electrode active material and the positive electrode additive as 100%, the mass fraction of WO3 is 0.1-2%, the mass fraction of ZnO is 0.1-2%, the mass fraction of Y2O3 is 0.1-2%, and the mass fraction of Yb2O3 is 0.1-2%.

[0049] The negative electrode of the nickel-hydrogen battery includes a negative electrode active material, a negative electrode additive and a negative electrode conductive agent. The negative electrode active material is an A2B7 type hydrogen storage alloy containing La, Pr, Nd, Ni, Al, Mg, Sm, Y and Zr. The negative electrode additive includes Y2O3. The negative electrode conductive agent includes nano-carbon tubes. Based on the total mass of the negative electrode active material, the negative electrode additive and the negative electrode conductive agent as 100%, the mass fraction of Yb2O3 is 0.1-2%, and the mass fraction of the nano-carbon tubes is 0.1-2%.

[0050] The preparation of the nickel-hydrogen battery provided in this embodiment includes the following steps:

[0051] Step 1, preparation of positive electrode: take 2 parts of adhesive and 40 parts of pure water, glue at a speed of 200r / min for 2-6h, then add positive electrode active material, positive electrode additive and positive electrode conductive agent at a mass ratio of 97:1:2, stir at a speed of 200r / min for 4h to obtain positive electrode slurry. Apply the prepared positive electrode slurry on the positive electrode skeleton with a coating thickness of 1.5mm. After coating, place it in an oven at 120℃ for 0.8h to dry the positive electrode slurry to obtain a positive electrode substrate, and finally cut it into strips, cut it into pieces, and spot weld the pole ears to obtain the positive electrode;

[0052] Step 2, preparation of negative electrode: Mix the negative electrode active material, negative electrode additive, binder and negative electrode conductive agent in a mass ratio of 97:1:1:1, and then mix with an appropriate amount of water to obtain a mixture slurry. Apply the mixture slurry on both sides of the core material made of iron punching metal that has been nickel-plated, with a coating thickness of 0.8mm. Dry the mixture slurry, and roll it together with the core material at room temperature with a pressure of 2000MPa, cut the obtained plate to obtain the negative electrode;

[0053] Step 3, preparation of nickel-hydrogen battery: take the positive electrode obtained in step 1 and the negative electrode obtained in step 2, wind them into a battery core with a diaphragm, install them into a nickel-plated steel shell, weld the cap, inject the electrolyte, and seal to obtain a nickel-hydrogen battery.

[0054] The binder includes xanthan gum, sodium polyacrylate, sodium carboxymethyl cellulose, hydroxypropyl methyl cellulose and polytetrafluoroethylene. The diaphragm is fluorinated polypropylene diaphragm paper. The electrolyte is a ternary electrolyte of sodium hydroxide, potassium hydroxide and lithium hydroxide, and the concentration of sodium hydroxide is 6 mol / L, the concentration of potassium hydroxide is 1.5 mol / L, and the concentration of lithium hydroxide is 0.5 mol / L.

[0055] Comparative Example 1

[0056] The existing AA-sized nickel-metal hydride battery has a nominal capacity of 2500 mAh.

[0057] The nickel-hydrogen batteries provided in Example 1 and Comparative Example 1 were left at room temperature for 24 hours and then activated. Then, the nickel-hydrogen batteries provided in Example 1 and Comparative Example 1 were tested as follows:

[0058] 1. Place a fully charged NiMH battery at 60°C for 35 days. See the results for the NiMH battery power retention. Figure 1 It can be seen that the power retention of the nickel-hydrogen battery provided in Example 1 is improved by about 30% compared with the power retention of the nickel-hydrogen battery provided in Comparative Example 1, and the improvement effect is more obvious with the increase of time or the increase of temperature.

[0059] 2. Place the NiMH battery at 50°C for 3 hours, then charge it at 0.1C for 16 hours. See the charging curve. Figure 2 From the charging curve, it can be seen that the charging voltage of the nickel-hydrogen battery provided in Example 1 at an ambient temperature of 50° C. increases significantly and an obvious inflection point appears, indicating that the charging efficiency of the nickel-hydrogen battery provided in Example 1 is significantly improved.

[0060] 3. Perform 1C / 1C cycle test on NiMH battery at room temperature. Figure 3 The number of cycles of the nickel-hydrogen battery provided in Example 1 is increased by about 40% relative to the number of cycles of the nickel-hydrogen battery provided in Comparative Example 1, which is a significant improvement.

[0061] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0062] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A nickel-hydrogen battery, comprising a positive electrode, a negative electrode, a separator and an electrolyte, characterized in that: The positive electrode comprises a positive electrode active material, a positive electrode additive and a positive electrode conductive agent, wherein the positive electrode active material is spherical nickel hydroxide coated with β-CoOOH, the positive electrode additive contains tungsten, zinc, yttrium and ytterbium, and the positive electrode conductive agent comprises graphene; The negative electrode includes a negative electrode active material, a negative electrode additive and a negative electrode conductive agent, wherein the negative electrode active material is an A2B7 type hydrogen storage alloy containing La, Pr, Nd, Ni, Al, Mg, Sm, Y and Zr, and the B position of the A2B7 type crystal structure does not contain cobalt, manganese, nickel and aluminum, the negative electrode additive includes yttrium oxide, and the negative electrode conductive agent includes carbon nanotubes; The electrolyte of the nickel-hydrogen battery is an alkaline aqueous solution prepared by using alkali metal hydroxide; The diaphragm is made of grafted or fluorinated or sulfonated polypropylene diaphragm paper; The tungsten in the positive electrode additive is derived from tungsten oxide, and the mass fraction of the tungsten oxide is 0.1-2% based on the total mass of the positive electrode active material and the positive electrode additive as 100%; The zinc in the positive electrode additive is derived from zinc oxide, and the mass fraction of the zinc oxide is 0.1-2% based on the total mass of the positive electrode active material and the positive electrode additive as 100%; The yttrium in the positive electrode additive is derived from yttrium oxide, and the mass fraction of the yttrium oxide is 0.1-2% based on the total mass of the positive electrode active material and the positive electrode additive as 100%; The ytterbium in the positive electrode additive is derived from ytterbium oxide, and the mass fraction of the ytterbium oxide is 0.1-2% based on the total mass of the positive electrode active material and the positive electrode additive as 100%; Taking the total mass of the negative electrode active material, the negative electrode additive and the negative electrode conductive agent as 100%, the mass fraction of the yttrium oxide is 0.1-2%, and the mass fraction of the carbon nanotubes is 0.1-2%.

2. The nickel-metal hydride battery according to claim 1, characterized in that: The alkali metal hydroxide includes potassium hydroxide, sodium hydroxide and lithium hydroxide, and the concentration of the alkali metal hydroxide is 5.5-9.0 mol / L.

3. The nickel-metal hydride battery according to claim 1, characterized in that: The spherical nickel hydroxide is coated with β-CoOOH by using a chemical vapor deposition process.

4. A method for preparing a nickel-hydrogen battery according to any one of claims 1 to 3, characterized in that: The steps include: Step 1, take a binder and pure water, glue at a speed of 150-300r / min for 2-6h, then add the positive electrode active material, the positive electrode additive and the positive electrode conductive agent, stir at a speed of 100-300r / min for 3-5h to obtain a positive electrode slurry, apply the prepared positive electrode slurry on the positive electrode skeleton, the coating thickness is 1.0-2.0mm, after the coating is completed, place it in an oven at 80-150°C for 0.5-1h to dry the positive electrode slurry to obtain a positive electrode substrate, and finally cut into strips, cut into pieces, and spot weld the pole ears to obtain a positive electrode; Step 2: Mix the negative electrode active material, the negative electrode additive, the binder, the negative electrode conductive agent and water to obtain a mixture slurry, apply the mixture slurry on both sides of a core material made of iron punching metal that has been nickel-plated, and the coating thickness is 0.5-1.0 mm. Dry the mixture slurry, and roll it together with the core material at room temperature with a pressure of 1500-3000 MPa, and cut the obtained plate to obtain a negative electrode; Step three, the positive electrode and the negative electrode are wound into a battery core with the separator, and the core is loaded into a nickel-plated steel shell, a cap is welded on, the electrolyte is injected, and the shell is sealed to obtain a nickel-hydrogen battery.

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