A cobalt-free nickel hydroxide positive electrode material, a preparation method thereof, a positive electrode sheet and a nickel-hydrogen battery

Abstract

The existing Co material is an indispensable component of the current nickel-hydrogen battery, and has problems of high cost and uneven resource distribution. The application provides a cobalt-free nickel hydroxide positive electrode material, a preparation method thereof, a positive electrode sheet and a nickel-hydrogen battery. The cobalt-free nickel hydroxide positive electrode material comprises an active substance and a conductive agent, the active substance is a compound shown in a chemical formula 1, and the porosity of the conductive agent is greater than 50%; Ni （1‑x1‑y1） Zn x1 X y1 (OH)2, the chemical formula 1; wherein 0≤x1≤0.1, 0≤y1≤0.05, X is a metal element in a water-soluble metal salt, and X does not include Ni and Zn elements. The cobalt-free nickel hydroxide positive electrode material provided by the application does not contain cobalt elements, significantly improves the battery gram capacity and cycle life, solves the problems of low safety, high cost and uneven resource distribution caused by cobalt resources, can get rid of the dependence of the nickel-hydrogen battery positive electrode material on cobalt, and improves the influence and market opportunities of cobalt-free products.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of nickel-hydrogen batteries, and particularly relates to a cobalt-free nickel hydroxide positive electrode material, a preparation method thereof, a positive electrode sheet and a nickel-hydrogen battery. BACKGROUND

[0002] Ni-MH batteries have the advantages of high specific energy, long cycle life, no memory effect, good overcharge and discharge capacity, high safety, good environmental compatibility, and wide working temperature range (-40-80 DEG C), and are widely used in various portable electronic products, electric tools, electric vehicles, modern military electronic equipment and aerospace fields. Cobalt is an indispensable component in the currently commercial nickel-hydrogen battery, which exists in the positive and negative electrodes of the battery. For the positive electrode, the conductivity of pure Ni(OH)2 is low (about 10 -17 S cm -1 ), and the conductivity and charging efficiency are often improved by surface coating and core solid solution of cobalt; in addition, 0.1%~10% of cobalt monoxide needs to be additionally added in the subsequent positive electrode sheet preparation process to further improve the conductivity. SUMMARY

[0003] In view of the problems of high cost and uneven resource distribution of the existing Co material as an indispensable component of the current nickel-hydrogen battery, the present application provides a cobalt-free nickel hydroxide positive electrode material, a preparation method thereof, a positive electrode sheet and a nickel-hydrogen battery.

[0004] In one aspect, the present application provides a cobalt-free nickel hydroxide positive electrode material, which comprises an active substance and a conductive agent, the active substance is a compound shown in chemical formula 1; the porosity of the conductive agent is >50%.

[0005] Ni （1-x1-y1） Zn x1 X y1 (OH)2, chemical formula 1;

[0006] Wherein, 0≤x1≤0.1, 0≤y1≤0.05, X is a metal element in a water-soluble metal salt, and X does not include Ni and Zn elements.

[0007] Preferably, X is selected from one or more of Ca, Y, Mg, Ti and Yb.

[0008] Preferably, the conductive agent is selected from expanded graphite, the particle size of the expanded graphite is 5-100 μm, the porosity is 80-95%, and the specific surface area is 50-150 m 2 / g;

[0009] The particle size of the active substance is 5-50 μm.

[0010] Preferably, the ratio of the D50 particle size D1 of the active substance to the D50 particle size D2 of the expanded graphite is a, a = D1 / D2;

[0011] The particle size of the expanded graphite includes one or more of the following particle size ranges: 5-20 μm, 20-40 μm, 40-60 μm, 60-80 μm, and 80-100 μm. The D50 particle size of the ith particle size range is denoted as di, and the mass ratio of the ith particle size range in the expanded graphite is denoted as fi, i ≥ 2.

[0012] D2= fi di , 0.15 ≤ a ≤ 2.

[0013] Preferably, the ratio of the mass of the active substance to the mass of the expanded graphite is b.

[0014] When the particle size of the expanded graphite is selected from one or both of the following ranges: 5-20 μm and 20-40 μm, b satisfies formula 1, Formula 1

[0015] When the particle size of the expanded graphite is selected from at least one of the following ranges: 40-60 um, 60-80 um, and 80-100 um, or the particle size of the expanded graphite is selected from at least one of the following ranges: 5-20 μm, 20-40 μm, and at least one of the following ranges: 40-60 um, 60-80 um, and 80-100 um, b satisfies formula 2, Formula 2; the electrode porosity is 20-40%;

[0016] 15 ≤ b ≤ 23.4.

[0017] In a second aspect, the present application provides a preparation method of the above-mentioned cobalt-free nickel hydroxide positive electrode material, which comprises the following steps:

[0018] Preparation of the active substance:

[0019] Obtaining solution A containing X, Ni, and Zn elements, wherein X is a metal element in a water-soluble metal salt, and X does not include Ni and Zn elements;

[0020] Obtaining solution B, which is an alkali solution;

[0021] Mixing and reacting the solution A and the solution B, and then purifying to obtain the active substance of the compound represented by formula 1;

[0022] Obtaining a conductive agent, and mixing the active substance with the conductive agent to obtain the cobalt-free nickel hydroxide positive electrode material.

[0023] Preferably, the obtaining of the solution A comprises the following steps:

[0024] mixing the water-soluble metal salt containing X, the water-soluble metal salt containing Ni, the water-soluble metal salt containing Zn in a molar ratio of y1:(1-x1-y1):x1 and water to obtain solution A, the molar concentration of the solution A being 1-5 mol / L;

[0025] The obtaining of the solution B comprises the following steps:

[0026] The caustic alkali and the complexing agent are mixed to obtain the solution B, the concentration of the caustic alkali being 0.5-3 mol / L, and the concentration of the complexing agent being 0.2-1 mol / L.

[0027] Preferably, the solution A and the solution B are mixed to react, and after the reaction is completed, the active substance of the compound shown in Chemical Formula 1 is purified by the following steps,

[0028] The solution A and the solution B are stirred and mixed, the pH value is adjusted to 8-11, the reaction is carried out at 50-80℃, the reaction time is 8-12 h, and after the reaction is completed, the standing is carried out for 8-24 h.

[0029] After the standing is completed, the solid substance is obtained by filtering and washing, the solid substance is dried at 60-100℃ for 8-24 h to obtain a solid powder, the solid powder is calcined at 200-500℃ for 3-5 h, and after the calcination is completed, the active substance of the compound shown in Chemical Formula 1 is obtained by crushing.

[0030] In a third aspect, the application provides a positive electrode sheet, comprising a positive electrode material, the positive electrode material being the cobalt-free nickel hydroxide positive electrode material described above or being prepared by the preparation method of the cobalt-free nickel hydroxide positive electrode material described above.

[0031] In a fourth aspect, the application provides a nickel-hydrogen battery, comprising a negative electrode sheet and the positive electrode sheet described above.

[0032] The cobalt-free nickel hydroxide positive electrode material provided by the application has the following effects: 1) the active substance is a compound shown in Chemical Formula 1, does not contain cobalt elements, and the active substance and the conductive agent can enable the electrode to form a complete and interconnected conductive network while maintaining good electrolyte infiltration, thereby realizing efficient utilization of the positive electrode active substance and significantly improving the battery capacity and cycle life; 2) the active substance and the conductive agent both do not contain cobalt elements, and when used in a nickel-hydrogen battery, the problems of low safety, high cost, uneven resource distribution and the like caused by cobalt resources can be solved, the dependence of the nickel-hydrogen battery positive electrode material on cobalt can be eliminated, and the influence of the cobalt-free product and market opportunities can be improved. DETAILED DESCRIPTION

[0033] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present application and not to limit the present application.

[0034] In order to illustrate the technical solutions of the present application, the following will be described by specific embodiments.

[0035] In an embodiment of the present application, the present application provides a cobalt-free nickel hydroxide positive electrode material, comprising an active substance and a conductive agent, wherein the active substance is a compound shown in chemical formula 1; and the porosity of the conductive agent is greater than 50%.

[0036] Ni （1-x1-y1） Zn x1 X y1 (OH)2, chemical formula 1.

[0037] In the formula, 0≤x1≤0.1, 0≤y1≤0.05, X is a metal element in a water-soluble metal salt, and X does not include Ni and Zn elements.

[0038] Specifically, the water-soluble metal salt refers to a soluble salt that can be dissolved in water at room temperature, and the soluble salt contains a metal element.

[0039] The porosity of the conductive agent is greater than 50%, the conductive agent has a porous structure, can be used to store electrolyte, increase the contact area of the electrolyte and the active substance, and improve the wettability of the electrode to the electrolyte; the conductive agent has high conductivity, and forms point-point contact or point-plane contact with the active substance, so that the obtained electrode is conducive to forming a complete and interconnected conductive network, thereby reducing the impedance of the electrode.

[0040] The cobalt-free nickel hydroxide positive electrode material provided by the present application has the following effects: 1) the active substance is a compound shown in chemical formula 1, does not contain cobalt element, and the active substance and the conductive agent can make the electrode form a complete and interconnected conductive network while maintaining good electrolyte wettability, thereby realizing efficient utilization of the positive electrode active substance and significantly improving the battery capacity and cycle life; 2) the active substance and the conductive agent both do not contain cobalt element, and can solve the problems of low safety, high cost and uneven resource distribution caused by cobalt resources in the nickel-hydrogen battery, so as to get rid of the dependence of the nickel-hydrogen battery positive electrode material on cobalt, and improve the influence and market opportunities of cobalt-free products.

[0041] In some embodiments, X is selected from one or more of Ca, Y, Mg, Ti, Yb.

[0042] Specifically, X is selected from one or more of Ca, Y, Mg, Ti, Yb, which can optimize the electrochemical performance of the positive electrode material, improve the structural stability of the positive electrode material, and improve the cycle performance of the nickel-hydrogen battery.

[0043] In some embodiments, the conductive agent is selected from expanded graphite having a particle size of 5-100 μm, a porosity of 80-95%, and a specific surface area of 50-150 m 2 / g; and the active material has a particle size of 5-50 μm.

[0044] In particular, the conductive agent is selected from expanded graphite having a particle size of 5-100 μm and a specific surface area of 50-150 m 2 / g, and the expanded graphite has a layered structure and can be wrapped around the surface of the active material or inserted between the spherical active material to form a continuous face-point contact conductive network, so that a good conductive network is formed between the active material particles and the expanded graphite, and the obtained electrode can form a complete conductive network structure; meanwhile, the expanded graphite has good toughness and can buffer the expansion of the active material; the expanded graphite has a porosity of 80-95% and a porous structure, which can increase the contact area of the electrolyte and the active material and improve the wettability of the electrode to the electrolyte.

[0045] The particle size of the expanded graphite is 5-100 μm, which is the overall particle size range of the expanded graphite.

[0046] In some embodiments, the pore size of the expanded graphite is 200-1300 nm.

[0047] The expanded graphite can be divided into several specifications according to the particle size, such as 5-20 μm, 20-40 μm, 40-60 μm, 60-80 μm, and 80-100 μm. When the particle size of the expanded graphite is 5-20 μm, the D50 particle size of the expanded graphite is 12.5 μm, the porosity of the expanded graphite is 95%, and the pore size of the expanded graphite is 200-400 nm; when the particle size of the expanded graphite is 20-40 μm, the D50 particle size of the expanded graphite is 30 μm, the porosity of the expanded graphite is 91%, and the pore size distribution of the expanded graphite is 400-600 nm; when the particle size of the expanded graphite is 40-60 μm, the porosity of the expanded graphite is 88%, the pore size distribution of the expanded graphite is 600-800 nm, and the D50 particle size of the expanded graphite is 50 μm; when the particle size of the expanded graphite is 60-80 μm, the D50 particle size of the expanded graphite is 70 μm, the porosity of the expanded graphite is 85%, and the pore size distribution of the expanded graphite is 800-1100 nm; and when the particle size of the expanded graphite is 80-100 μm, the D50 particle size of the expanded graphite is 90 μm, the porosity of the expanded graphite is 80%, and the pore size distribution of the expanded graphite is 1000-1300 nm.

[0048] In some embodiments, the ratio of the D50 particle size of the active material D1 to the D50 particle size of the expanded graphite D2 is a, a = D1 / D2, the particle size of the expanded graphite includes one or more of the following particle size ranges: 5-20 μm, 20-40 μm, 40-60 μm, 60-80 μm, 80-100 μm, the D50 particle size of the i-th particle size range is denoted as di, and the mass ratio of the i-th particle size range in the expanded graphite is denoted as fi, i ≥ 1.

[0049] D2= , 0.15 ≤ a ≤ 2.

[0050] Specifically, the ratio a of the D50 particle size of the active material to the D50 particle size of the expanded graphite is in the range of 0.15-2, which is beneficial to the synergistic effect between the expanded graphite and the active material, and is beneficial to the expanded graphite being wrapped on the surface of the active material or being interspersed between the spherical active material, forming a continuous face-point contact conductive network, so that a better conductive network is formed between the active material particles and the expanded graphite, and the obtained electrode can constitute a complete conductive network structure; at the same time, the expanded graphite can store electrolyte, so that the electrode has a good effect of infiltrating electrolyte.

[0051] If a is less than 0.15, the particle size of the expanded graphite is too large, and a continuous and interconnected conductive network structure cannot be formed between the active material and the expanded graphite, the obtained electrode cannot constitute a complete conductive network structure, the conductivity of the electrode is reduced, the active material cannot fully participate in the reaction, ion diffusion is blocked, and polarization is increased; if a is greater than 2, the particle size ratio is too large to block the pores of the electrode, affect the penetration of electrolyte, and reduce the cycle life of the battery.

[0052] The particle size of the expanded graphite includes one or more of the following particle size ranges: 5-20 μm, 20-40 μm, 40-60 μm, 60-80 μm, 80-100 μm, the D50 particle size of the i-th particle size range is denoted as di, and the mass ratio of the i-th particle size range in the expanded graphite is denoted as fi, i ≥ 2.

[0053] Specifically, when i = 2, it means that the expanded graphite contains two particle size ranges, such as two of the following particle size ranges: 5-20 μm, 20-40 μm, 40-60 μm, 60-80 μm, or 80-100 μm, i = 1 is one of the two particle size ranges, which is recorded as expanded graphite 1, and i = 2 is the other one of the two particle size ranges, which is recorded as expanded graphite 2. i = 1, f1 is the mass of expanded graphite 1 / (mass of expanded graphite 1 + mass of expanded graphite 2), and d1 is the D50 particle size in expanded graphite 1. i = 2, f2 is the mass of expanded graphite 2 / (mass of expanded graphite 1 + mass of expanded graphite 2), and d2 is the D50 particle size in expanded graphite 2.

[0054] When i=3, it means that the expanded graphite contains three particle size ranges, such as three particle size ranges of 5-20 μm, 20-40 μm, 40-60 μm, 60-80 μm or 80-100 μm, the three particle size ranges are defined as expanded graphite 1, expanded graphite 2 and expanded graphite 3, f1 is the mass of expanded graphite 1 / (mass of expanded graphite 1+mass of expanded graphite 2+mass of expanded graphite 3), d1 is the D50 particle size in expanded graphite 1. f2 is the mass of expanded graphite 2 / (mass of expanded graphite 1+mass of expanded graphite 2+mass of expanded graphite 3), d2 is the D50 particle size in expanded graphite 2. f3 is the mass of expanded graphite 3 / (mass of expanded graphite 1+mass of expanded graphite 2+mass of expanded graphite 3), d3 is the D50 particle size in expanded graphite 3. Similarly, i=4, i=5 are calculated in the same way, which will not be repeated here.

[0055] D2= When there is only one particle size range in the expanded graphite, i=1, D2 is the corresponding D50 particle size,

[0056] The ratio of the D50 particle size D1 of the active substance to the D50 particle size D2 of the expanded graphite is a, a=D1 / D2; when there is only one particle size range in the expanded graphite, D2 is the D50 particle size value corresponding to this particle size range. When the expanded graphite contains two or more particle size ranges, D2 is calculated as D2= , to obtain the corresponding D2 value. For example, when the expanded graphite contains two particle size ranges, D2= ((f1*d1 -1.3 + (f2*d2 -1.3 ) （-1 / 1.3） , f1 is the mass of expanded graphite 1 / (mass of expanded graphite 1+mass of expanded graphite 2), d1 is the D50 particle size in expanded graphite 1. i=2, f2 is the mass of expanded graphite 2 / (mass of expanded graphite 1+mass of expanded graphite 2), d2 is the D50 particle size in expanded graphite 2.

[0057] In some embodiments, the ratio of the mass of the active substance to the mass of the expanded graphite is b;

[0058] When the particle size of the expanded graphite is selected from one or two of 5-20 μm and 20-40 μm, b satisfies formula 1, Formula 1;

[0059] When the particle size of the expanded graphite is selected from at least one of 40-60 um, 60-80 um, 80-100 um or the particle size of the expanded graphite is selected from at least one of 5-20 um, 20-40 um and 40-60 um, 60-80 um, 80-100 um, b satisfies formula 2, Formula 2; the electrode porosity is 20-40%;

[0060] 15≤b≤23.4.

[0061] Specifically, when calculating the value of b, the calculation method of b is different due to the different particle size ranges of the expanded graphite. When the particle size of the expanded graphite is in the range of 5-20 um, or the particle size of the expanded graphite is in the range of 20-40 um, or the expanded graphite with particle size in the range of 5-20 um and particle size in the range of 20-40 um is mixed, when calculating b, the formula is used, where a is the ratio of the D50 particle size D1 of the active material to the D50 particle size D2 of the expanded graphite.

[0062] In addition to the case where the particle size of the expanded graphite is in the range of 5-20 um, or the particle size of the expanded graphite is in the range of 20-40 um, or the expanded graphite with particle size in the range of 5-20 um and particle size in the range of 20-40 um is mixed, the value of b is calculated using the formula , where a is the ratio of the particle size D1 of the active material to the particle size D2 of the expanded graphite, and the electrode porosity is in the range of 20-40%.

[0063] For the electrode porosity, the test method is: , where p 电极 is the electrode density (g / cm³), i.e. the density of the positive electrode sheet, and p 材料 is the theoretical maximum density of the cobalt-free nickel hydroxide positive electrode material (g / cm³).

[0064] The electrode porosity here is the porosity of the positive electrode sheet. The electrode porosity is different due to different preparation methods of the positive electrode sheet. The application does not limit the preparation method of the positive electrode sheet, as long as the prepared positive electrode sheet has a porosity in the range of 20-40%.

[0065] Specifically, the ratio b of the mass of the active material to the mass of the expanded graphite satisfies the condition 15≤b≤23.4, which is beneficial to the formation of a continuous conductive network by the active material and the conductive agent, so that the electrode forms a complete and interconnected conductive network, thereby realizing efficient utilization of the positive electrode active material and significantly improving the battery capacity and cycle life. If b is too large, the content of the expanded graphite is small, and the active material forms a dead zone because it is not connected to the conductive network; if b is too small, the excess expanded graphite fills the electrode pores, hindering ion transport.

[0066] In some preferred embodiments, the cobalt-free nickel hydroxide positive electrode material satisfies a satisfies 0.15≤a≤2, b satisfies 15≤b≤23.4, the specific surface area of the expanded graphite is in the range of 50m 2 / g≤c≤150m 2 / g, which is beneficial to the formation of a continuous conductive network of the active material and the expanded graphite. The obtained electrode not only has good electrolyte wettability, but also has a complete and interconnected conductive network, thereby realizing the maximum utilization of the positive electrode active material, and the assembled battery exhibits high specific capacity and long cycle life.

[0067] In some preferred embodiments, the cobalt-free nickel hydroxide positive electrode material is composed of an active material and a conductive agent.

[0068] In a second aspect, the application provides a preparation method of the cobalt-free nickel hydroxide positive electrode material described above, which comprises the following steps:

[0069] Preparation:

[0070] A solution A containing X, Ni and Zn elements is obtained, wherein X is a metal element in a water-soluble metal salt, and X does not include Ni and Zn elements;

[0071] A solution B is obtained, which is an alkali solution;

[0072] The solution A and the solution B are mixed and reacted, and after the reaction is completed, the active material of the compound represented by Chemical Formula 1 is obtained by purification;

[0073] A conductive agent is obtained, and the active material is mixed with the conductive agent to obtain the cobalt-free nickel hydroxide positive electrode material.

[0074] The preparation method of the cobalt-free nickel hydroxide positive electrode material provided by the application, the preparation method of the active material of the compound represented by Chemical Formula 1 is simple, and the nickel hydroxide positive electrode material can be obtained by directly mixing the active material with a conductive agent. The preparation method is simple, the cost is low, the cobalt-free nickel hydroxide positive electrode material obtained is used in a battery, which can effectively improve the specific capacity and cycle life of the battery. At the same time, the positive electrode material does not contain cobalt elements, which can solve the problems of low safety, high cost and uneven distribution of cobalt resources in nickel-hydrogen batteries, and can break the dependence of nickel-hydrogen battery positive electrode materials on cobalt, thereby improving the influence of cobalt-free products and market opportunities.

[0075] In some embodiments, the obtaining of the solution A comprises the following steps:

[0076] The water-soluble metal salt containing X, the water-soluble metal salt containing Ni, and the water-soluble metal salt containing Zn are mixed with water in a molar ratio of y1:(1-x1-y1):x1 to obtain the solution A, and the molar concentration of the solution A is 1-5 mol / L;

[0077] The solution B is obtained by the following steps:

[0078] The caustic alkali has a concentration of 0.5-3 mol / L, and the complexing agent has a concentration of 0.2-1 mol / L.

[0079] Specifically, the water-soluble metal salt containing X, the water-soluble metal salt containing Ni, and the water-soluble metal salt containing Zn are mixed with water in a molar ratio of y1:(1-x1-y1):x1 according to the structure shown in Chemical Formula 1 to obtain the solution A. The solution A is simple to prepare. The molar concentration of the solution A is 1-5 mol / L, which means that the molar amount of X, Ni, and Zn contained in each liter of the solution A is 1-5 mol.

[0080] The solution B is a mixed solution containing caustic alkali and complexing agent. The concentration of the caustic alkali is 0.5-3 mol / L, which means that the concentration of the caustic alkali in the solution B is in the range of 0.5-3 mol / L. The concentration of the complexing agent is 0.2-1 mol / L, which means that the concentration of the complexing agent in the solution B is in the range of 0.2-1 mol / L. The caustic alkali includes one or both of NaOH and KOH. The complexing agent includes one or both of ammonia and ammonium salt. The concentration of the caustic alkali in the solution B can be in the following ranges: 0.5-1.0 mol / L, 1.0-1.5 mol / L, 1.5-2.0 mol / L, or 2.0-3.0 mol / L. The concentration of the complexing agent in the solution B can be in the following ranges: 0.2-0.4 mol / L, 0.4-0.6 mol / L, 0.6-0.8 mol / L, or 0.8-1.0 mol / L. The ammonium salt includes one or more of ammonium sulfate.

[0081] The solution A contains X, Ni, and Zn metal elements, and the solution B is an alkali solution. The solution A and the solution B are mixed, and in the alkaline environment, nickel ions, zinc ions, and the like react with hydroxyl ions to form co-precipitation.

[0082] In some embodiments, the water-soluble metal salt containing X is selected from one or more of a nitrate containing X, a chloride containing X, and a sulfate containing X, and X does not contain Ni and Zn.

[0083] The water-soluble metal salt containing Ni is selected from one or more of nickel nitrate, nickel chloride, and nickel sulfate.

[0084] The water-soluble metal salt containing Zn is selected from one or more of zinc nitrate, zinc chloride, and zinc sulfate.

[0085] The inorganic strong alkali includes sodium hydroxide, and the inorganic weak alkali includes ammonia.

[0086] Specifically, the water-soluble metal salt containing X is selected from one or more of a nitrate salt containing X, a chloride salt containing X, and a sulfate salt containing X, X not containing Ni and Zn.

[0087] X is a metal element in the water-soluble metal salt.

[0088] When X is selected from Ca, the nitrate salt containing X is calcium nitrate, the chloride salt containing X is calcium chloride, and the sulfate salt containing X is calcium sulfate. Similarly, when X is selected from Y, Mg, Ti, or Yb, respectively, the same reasoning applies.

[0089] The alkali metal hydroxide is selected from sodium hydroxide, potassium hydroxide, and the like.

[0090] In some embodiments, the solution A and the solution B are mixed and reacted, and after the reaction is completed, the active substance of the compound of Formula 1 is purified by the following steps,

[0091] The solution A and the solution B are stirred and mixed, and the pH value is adjusted to 8-11, and the reaction is carried out at 50-80°C, and the reaction time is 8-12h, and after the reaction is completed, it is placed for 8-24h.

[0092] After the standing is completed, the solid substance is obtained by filtering and washing, and the solid substance is dried at 60-100°C for 8-24h to obtain a solid powder, and the solid powder is calcined at 200-500°C for 3-5h, and after the calcination is completed, the active substance of the compound of Formula 1 is obtained by crushing.

[0093] Specifically, the solution A and the solution B are stirred and mixed, which can be slowly adding solution B to solution A while continuously stirring, or slowly adding solution A to solution B while continuously stirring.

[0094] The pH value is adjusted to 8-11 in order to form an alkaline environment, so that in the alkaline environment, nickel ions, zinc ions, etc. react with hydroxyl ions to form coprecipitation.

[0095] In the range of 50-80°C, it is beneficial for nickel ions, zinc ions, etc. to react with hydroxyl ions to form coprecipitation. The reaction temperature can be 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, etc. The reaction time can be 8-9h, 9-10h, 10-11h, or 11-12h.

[0096] After the standing is completed, the filter cake is obtained by filtering, and the filter cake is washed at least once with deionized water, and the washing liquid after washing is neutral, so as to remove possible impurity ions, and the solid substance is obtained after the washing is completed.

[0097] The solid substance is placed in a drying device for drying, the drying temperature is 60-100°C, the drying time is 8-24h, and the solid powder is obtained after the drying is completed.

[0098] The dried solid powder is placed in a calcination device for calcination, the calcination temperature is 200-500℃, and the calcination time is 3-5h. Within the calcination temperature and the calcination time, the crystal growth and the solid solution of the X element in the nickel hydroxide can be promoted. After the calcination is completed, the product is naturally cooled to room temperature (15-35℃), and then the product is crushed. After the crushing is completed, the product Ni （1-x1-y1） Zn x1 X y1 (OH) 2， wherein 0≤x1≤0.1, 0≤y1≤0.05, X is a metal element in a water-soluble metal salt, and X does not include Ni and Zn elements.

[0099] The crushing includes grinding or ball milling.

[0100] In some embodiments, obtaining the conductive agent includes the following steps:

[0101] The graphite, the oxidizing agent, the inorganic acid, and the intercalation agent are mixed, reacted at 40-60℃ for 60-120min, and then washed to obtain a product A. The product A is heated at 600-1000℃ for 5-30s, and then crushed to obtain the expanded graphite.

[0102] The oxidizing agent includes potassium permanganate, the inorganic acid includes concentrated sulfuric acid, and the intercalation agent includes ferric chloride.

[0103] The volume of the inorganic acid added per gram of the graphite is 3-5ml;

[0104] The mass ratio of the graphite to the oxidizing agent is 1:(0.05-0.2);

[0105] The mass ratio of the graphite to the intercalation agent is 1:(0.002-0.02);

[0106] The particle size of the graphite is 1-50μm.

[0107] Specifically, in the preparation of the conductive agent, the concentrated sulfuric acid serves as a carrier for intercalation, provides intercalation ions and a reaction environment, the potassium permanganate serves as an oxidizing agent, oxidizes and activates the graphite layer, promotes intercalation, the iron oxide enhances the oxidation effect and optimizes the intercalation structure, the graphite with intercalation is obtained after reacting at 40-60℃ for 60-120min, and then the graphite with intercalation is heated at 600-1000℃ for 5-30s. The interlayer compound is decomposed to generate gas, which pushes the graphite layer to expand rapidly, and the expanded graphite with pores is obtained.

[0108] The product A obtained after the reaction is washed, including the following steps: after the reaction is completed, sodium hydroxide solution is added for immersion washing, the immersion washing time is 30-60 min, after the immersion washing is completed, deionized water is used for washing until neutral, and then drying is performed to obtain the product A.

[0109] After the heating is completed, the expanded graphite is obtained by crushing, including the following steps: after the heating is completed, ball milling treatment is performed for 10-30 min at a rotating speed of 200-2000 rpm, to obtain the expanded graphite.

[0110] The preparation method of the conductive agent, the expanded graphite obtained by the preparation method has a particle size of 5-100 mu m, a porosity of 80-95%, and a specific surface area of 50-150 m 2 / g.

[0111] The volume of the inorganic acid added per gram of the graphite is in a range of 3-5 mL, facilitating the HSO4 - , SO4 2- In the reaction, the graphite layer can be embedded between the graphite layers, the intercalation ions and the reaction environment are provided.

[0112] The mass ratio of the graphite to the oxidizing agent is controlled in a range of 1:(0.05-0.2), which is beneficial to the oxidation of part of the carbon atoms on the surface edge of the graphite layer by the oxidizing agent, the moderate oxidation increases the active sites of the graphite layer, and promotes the intercalation reaction. Specifically, the mass ratio of the graphite to the oxidizing agent can be in a range of 1:(0.05-0.08), 1:(0.08-0.1), 1:(0.1-0.15) or 1:(0.15-0.2)

[0113] The mass ratio of the graphite to the intercalation agent is controlled in a range of 1:(0.002-0.02), which is synergistic with the oxidizing agent, enhances the oxidation effect, and promotes the intercalation reaction. Specifically, the mass ratio of the graphite to the intercalation agent can be in a range of 1:(0.002-0.008), 1:(0.008-0.01), 1:(0.01-0.015) or 1:(0.015-0.02)

[0114] In a third aspect, the application provides a positive electrode sheet, including a positive electrode material, the positive electrode material being the cobalt-free nickel hydroxide positive electrode material or being prepared by the preparation method of the cobalt-free nickel hydroxide positive electrode material.

[0115] The positive electrode sheet provided by the application contains the cobalt-free nickel hydroxide positive electrode material, the active material and the conductive agent can enable the electrode to form a complete and interconnected conductive network while maintaining good electrolyte infiltration, thereby realizing efficient utilization of the positive electrode active material and significantly improving the battery capacity and cycle life.

[0116] The positive electrode sheet further comprises an additive and a binder, the additive comprises one or more of TiO2, Y2O3, Yb2O3, Er2O3, Ca(OH)2, Tm2O3, and Lu2O3, and the binder comprises one or more of carboxymethyl cellulose, carboxyethyl cellulose, hydroxyethyl cellulose, hydroxypropyl methyl cellulose, sodium polyacrylate, polytetrafluoroethylene, butadiene rubber sodium alginate, and chitosan.

[0117] In a fourth aspect, the present application provides a nickel-hydrogen battery comprising a negative electrode sheet and the positive electrode sheet described above.

[0118] The nickel-hydrogen battery provided by the present application does not contain cobalt elements in the positive electrode material, which can solve the problems of low safety, high cost, uneven resource distribution and the like caused by cobalt resources in the nickel-hydrogen battery, and can break the dependence of the nickel-hydrogen battery positive electrode material on cobalt, improve the influence and market opportunities of cobalt-free products; meanwhile, the active material and conductive agent contained in the positive electrode material can enable the electrode to form a complete and interconnected conductive network while maintaining good electrolyte infiltration, thereby realizing efficient utilization of the positive electrode active material and significantly improving the nickel-hydrogen battery specific capacity and cycle life.

[0119] The preparation of the negative electrode sheet is the prior art, which will not be described here.

[0120] The present application is further described below through examples.

[0121] Example 1

[0122] 1) Preparation of the positive electrode material

[0123] S1: Preparation of the active material

[0124] S11: Obtain solution A: dissolve nickel nitrate, zinc nitrate, and magnesium nitrate in deionized water according to a molar ratio of (1-x1-y1):x1:y1 to prepare a 2.0 mol / L mixed solution A; wherein x1=0.05, y1=0.02, and 1-x1-y1=0.93.

[0125] S12: Obtain solution B: uniformly mix deionized water, sodium hydroxide, and ammonia water to obtain solution B, wherein the concentration of sodium hydroxide in solution B is 2 mol / L, and the concentration of ammonia water is 0.5 mol / L.

[0126] S13: Slowly add solution B to solution A while continuously stirring, adjust the pH value to 10, react for 10 h, the reaction temperature is 60℃, and after the reaction is completed, stand for 15 h; filter the generated precipitate and repeatedly wash with deionized water until the washing liquid is neutral to remove possible impurity ions.

[0127] The washed solid material is placed in an oven and dried at 80°C for 18 hours. The dried solid powder is placed in a muffle furnace and calcined at 300°C for 4 hours. After calcination, the product is naturally cooled to room temperature and then ground at 800 rpm for 30 min to obtain Ni(OH)2active material with a particle size of 5-30 μm. 0.93 Zn 0.05 Mg 0.02 (OH)2active material. The D50 particle size of the active material is 18 μm.

[0128] S2: Preparation of expanded graphite

[0129] 2.0 L of concentrated sulfuric acid is added with 500 g of natural graphite with a particle size of 1-50 μm while stirring, 75 g of potassium permanganate and 5 g of ferric chloride are added, and the reaction is carried out at 50°C for 80 min. After the reaction is completed, the expandable graphite is obtained by immersing in 0.3 mol / L NaOH for 60 min and washing with deionized water until neutral and then drying. The expandable graphite is rapidly heated at 800°C for 30 s to obtain expanded graphite. The obtained expanded graphite is subjected to ball milling at a rotation speed of 1500 rpm for 30 min to obtain expanded graphite with a particle size of 20-40 μm, a porosity of 91%, a specific surface area of 120 m² / g, a pore size of 400-600 nm, and a D50 particle size of 30 μm.

[0130] S3: Preparation of cobalt-free nickel hydroxide positive electrode material

[0131] The Ni(OH)2active material prepared in step S1 is mixed with the expanded graphite prepared in step S2 to obtain a cobalt-free nickel hydroxide positive electrode material. The D50 particle size of the Ni(OH)2active material is 18 μm. 0.93 Zn 0.05 Mg 0.02 (OH)2active material and the expanded graphite prepared in step S2. The D50 particle size of the Ni(OH)2active material is 18 μm. 0.93 Zn 0.05 Mg 0.02 The ratio a of the D50 particle size D1 of the Ni(OH)2to the D50 particle size D2 of the expanded graphite is D1 / D2=0.6.

[0132] Ni 0.93 Zn 0.05 Mg 0.02 (OH)2and the expanded graphite is b= =23.4;

[0133] 2) Preparation of positive electrode sheet

[0134] The cobalt-free nickel hydroxide positive electrode material obtained in step S3, 88 parts, a binder (carboxymethyl cellulose, carboxyethyl cellulose, hydroxyethyl cellulose), 2 parts, an additive (TiO2, Y2O3, Yb2O3), 2 parts, and deionized water, 3 parts, are sequentially added into a vacuum stirring machine, the stirring speed is controlled to be 250 r / min, and the stirring is performed for 150 min, so that the positive electrode active material is uniformly dispersed to form a positive electrode slurry. Then, the positive electrode slurry is subjected to slurry drawing, drying, sheet pressing, and cutting to form a positive electrode sheet.

[0135] 3) Preparation of the negative electrode sheet

[0136] The dispersing binder, 2 parts, a negative electrode conductive agent, 2 parts, the negative electrode active material, 92 parts, a negative electrode additive, 1 part, and deionized water, 3 parts, are sequentially added into a vacuum stirring machine, the stirring speed is controlled to be 250 r / min, and the stirring is performed for 120 min, so that the active material is uniformly dispersed. Then, 3 parts of polytetrafluoroethylene and 1.8 parts of butadiene-styrene rubber are added, the stirring speed is controlled to be 200 r / min, and the stirring is performed for 10 min. The solid content of the slurry is controlled to be 80%, the slurry is transferred to a slurry drawing hopper, the liquid level is controlled to be 16 cm, a nickel-plated steel belt with a thickness of 0.06 mm is used as a substrate, and the slurry is subjected to slurry drawing, sheet drying, roller pressing, and cutting to form a negative electrode sheet.

[0137] The dispersing binder is HPMC, the negative electrode conductive agent is 0.3% carbon black + 1.7% nickel powder, the negative electrode active material is an A2B7 alloy (the formula is La 0.17 Pr 0.051 Nd 0.124 Sm 0.40 Y 0.01 Mg 0.15 Ni 3.28 Al 0.16 Zr 0.004 ), and the negative electrode additive is Y2O3.

[0138] 4) Assembly of the battery

[0139] The above positive electrode sheet and negative electrode sheet, and a Japanese imported separator with a surface density of 54 g / m 2 , a thickness of 0.15 mm, a low sulfonation degree, and added superfine fibers, are wound into a steel shell, and an electrolyte composed of potassium hydroxide / sodium hydroxide / lithium hydroxide / pure water, OH - with a concentration of 5.6 mol / L, is injected, and the opening is sealed to form a 3A750 battery core.

[0140] Example 2

[0141] The procedure of this example is the same as that of Example 1, except that the ball milling step in the S2 step of this example is different, and the rest is the same as that of Example 1. Specifically, the obtained expanded graphite is divided into two parts, one part is subjected to ball milling at a speed of 2000 rpm for 40 min, and the obtained product is recorded as expanded graphite 2-1, which has a particle size of 5-20 μm, a porosity of 95%, a pore size of 200-400 nm, and a specific surface area of 150 m² / g. The D50 particle size of the expanded graphite 2-1 is 12.5 μm. The other part is subjected to ball milling at a speed of 1500 rpm for 30 min, and the obtained product is recorded as expanded graphite 2-2, which has a particle size of 20-40 μm, a porosity of 91%, a specific surface area of 120 m² / g, and a pore size of 400-600 nm. The D50 particle size of the expanded graphite 2-2 is 30 μm.

[0142] In the total expanded graphite, the expanded graphite 2-1 accounts for 50% by mass of the total expanded graphite, and the expanded graphite 2-2 accounts for 50% by mass of the total expanded graphite.

[0143] Example 3

[0144] The procedure of this example is the same as that of Example 1, except that the ball milling step in the S2 step of this example is different, and the rest is the same as that of Example 1. Specifically, the obtained expanded graphite is divided into two parts, one part is subjected to ball milling at a speed of 1000 rpm for 30 min, and the obtained product is recorded as expanded graphite 3-1, which has a particle size of 40-60 μm, a porosity of 88%, a pore size of 600-800 nm, and a specific surface area of 100 m² / g. The D50 particle size of the expanded graphite 3-1 is 50 μm. The other part is subjected to ball milling at a speed of 1500 rpm for 30 min, and the obtained product is recorded as expanded graphite 3-2, which has a particle size of 20-40 μm, a porosity of 91%, a specific surface area of 120 m² / g, and a pore size of 400-600 nm. The D50 particle size of the expanded graphite 3-2 is 30 μm.

[0145] In the total expanded graphite, the expanded graphite 3-1 accounts for 30% by mass of the total expanded graphite, and the expanded graphite 3-2 accounts for 70% by mass of the total expanded graphite.

[0146] Example 4

[0147] The sub-step of this example and example 1 is the same, the difference is that the ball milling step in S2 step of this example is different, the rest is the same as example 1; as follows. In this example, the obtained expanded graphite is divided into two parts, one part is subjected to 30 min of ball milling treatment at a speed of 1300 rpm, the obtained product is recorded as expanded graphite 4-1, the particle size is 20-40 μm, the porosity is 91%, the pore size is 400-600 nm, the specific surface area is 120 m² / g, the D50 particle size of expanded graphite 4-1 is 30 μm. The other part is subjected to 10 min of ball milling treatment at a speed of 1000 rpm, the obtained product is recorded as expanded graphite 4-2, the particle size is 60-80 μm, the porosity is 85%, the specific surface area is 80 m² / g, the pore size is 800-1100 nm, the D50 particle size of expanded graphite 4-2 is 70 μm.

[0148] In the total expanded graphite, the mass ratio of expanded graphite 4-1 to the total expanded graphite is 80%, and the mass ratio of expanded graphite 4-2 to the total expanded graphite is 20%.

[0149] Example 5

[0150] The sub-step of this example and example 1 is the same, the difference is that the ball milling step in S2 step of this example is different, the rest is the same as example 1; as follows. In this example, the obtained expanded graphite is subjected to 10 min of ball milling treatment at a speed of 150 rpm, the obtained product is recorded as expanded graphite, the particle size is 90-120 μm, the porosity is 76%, the specific surface area is 40 m² / g, the pore size is 1300-1600 nm, the D50 particle size of expanded graphite is 110 μm. Among them, the mass ratio of Ni 0.93 Zn 0.05 Mg 0.02 The mass ratio of (OH)2 to expanded graphite is 23.4.

[0151] Example 6

[0152] The sub-step of example 6 and example 1 is the same, the difference is that the values of x1 and y1 are different, see table 1 for details; the particle size of the active material obtained in S13 step is 5-25 μm, the D50 particle size is 16 μm. The rest is the same as example 1.

[0153] Example 7

[0154] The sub-step of example 7 and example 1 is the same, the difference is that the values of x1 and y1 are different, see table 1 for details; the particle size of the active material obtained in S13 step is 5-25 μm, the D50 particle size is 15 μm. The rest is the same as example 1.

[0155] Example 8

[0156] The most steps of this example and example 1 are the same, the difference is that: the S1 step of this example changes the rotation speed of grinding so that the D50 particle size of the active substance is 12 μm; the S2 step of this example adjusts the rotation speed and the ball milling time, so that the particle size of the expanded graphite is in the range of 5-100 microns, and the D50 particle size is 90 μm. The rest is the same as example 1.

[0157] Example 9

[0158] The most steps of this example and example 1 are the same, the difference is that: the S1 step of this example changes the rotation speed of grinding so that the D50 particle size of the active substance is 12 μm; the S2 step of this example adjusts the rotation speed and the ball milling time, so that the particle size of the expanded graphite is in the range of 5-100 microns, and the D50 particle size is 90 μm. The rest is the same as example 1.

[0159] Example 10

[0160] The most steps of this example and example 1 are the same, the difference is that: the S1 step of this example changes the rotation speed of grinding so that the D50 particle size of the active substance is 12 μm; the S2 step of this example adjusts the rotation speed and the ball milling time, so that the particle size of the expanded graphite is in the range of 5-100 microns, and the D50 particle size is 90 μm. The rest is the same as example 1.

[0161] Example 11

[0162] The most steps of this example and example 1 are the same, the difference is that: the S1 step of this example changes the rotation speed of grinding so that the D50 particle size of the active substance is 12 μm; the S2 step of this example adjusts the rotation speed and the ball milling time, so that the particle size of the expanded graphite is in the range of 5-100 microns, and the D50 particle size is 90 μm. The rest is the same as example 1.

[0163] Example 12

[0164] The most steps of this example and example 5 are the same, the difference is that: the S1 step of this example changes the rotation speed of grinding so that the D50 particle size of the active substance is 12 μm; the S2 step of this example adjusts the rotation speed and the ball milling time, so that the particle size of the expanded graphite is in the range of 5-100 microns, and the D50 particle size is 90 μm. The rest is the same as example 1.

[0165] Example 13

[0166] The present embodiment and most of the steps of Example 1 are the same, except that the conductive agent does not use expanded graphite, and the conductive agent is a commercially available natural graphite. The particle size of the natural graphite used is 20-40 μm, the porosity is 65%, the specific surface area is 6 m² / g, and the D50 particle size of the natural graphite is 28 μm. Among them, the mass ratio of Ni(OH)2to natural graphite is still 23.4. 0.93 Zn 0.05 Mg 0.02 The mass ratio of Ni(OH)2to natural graphite is still 23.4.

[0167] Comparative Example 1

[0168] The present comparative example and most of the steps of Example 1 are the same, except that the values of x1 and y1 are different, as shown in Table 1. The particle size of the active material obtained in step S13 of Comparative Example 1 is 5-30 μm, and the D50 particle size is 18 μm. The rest is the same as Example 1.

[0169] Comparative Example 2

[0170] The present comparative example and most of the steps of Example 1 are the same, except that the conductive agent of the present comparative example is carbon black, and the porosity of the conductive agent is 35%. The rest is the same as Example 1.

[0171] Comparative Example 3

[0172] The present comparative example and most of the steps of Example 1 are the same, except that the present comparative example has no conductive agent, and the rest is the same as Example 1.

[0173] The values of a and b calculated from the active material and expanded graphite obtained in each of the above examples and comparative examples are shown in Table 1. Among them, the porosity of the positive electrode sheet obtained in each of the examples and comparative examples is shown in Table 1.

[0174] Among them, the porosity test method of the positive electrode sheet is as follows: . Among them, ρ 电极 is the density of the positive electrode sheet (g / cm³), and ρmaterial is the theoretical maximum density of the cobalt-free nickel hydroxide positive electrode material prepared in step S3.

[0175] Among them, the area density of the positive electrode sheet is the mass of the positive electrode active material layer / volume of the positive electrode sheet.

[0176] The theoretical maximum density of the cobalt-free nickel hydroxide positive electrode material = total mass of the active material and the conductive agent / total volume of the active material and the conductive agent.

[0177] Table 1

[0178]

[0179] Note that the above Example 5 is directly artificially limited to a ratio of the mass of the active substance to the mass of the expanded graphite of 23.4.

[0180] Performance test

[0181] The nickel-hydrogen batteries prepared in each of the above examples and the comparative examples were subjected to the following performance test.

[0182] Gram capacity

[0183] Formation method: (1) charging at 150 mA for 100 min, and then discharging at 150 mA to 1.0 V; (2) charging at 75 mA for 200 min, and then discharging at 150 mA to 1.0 V; (3) charging at 150 mA for 300 min, and then discharging at 150 mA to 1.0 V.

[0184] After the formation, the nickel-hydrogen batteries of each example and the comparative example were subjected to three IEC capacity tests, and the battery gram capacity = the third IEC capacity / the amount of powder on the positive plate. The amount of powder on the positive plate refers to the total mass of the solid powder on the positive plate.

[0185] 25℃ cycle performance

[0186] The above obtained battery was charged at 750 mA for 72 min, rested for 30 min, and then discharged at 750 mA to 1 V; the above charging and discharging test was repeated until the battery capacity was attenuated to 60% of the first discharge capacity. The battery capacity after each cycle test was recorded.

[0187] The above electrical performance test results are shown in Table 2.

[0188] Table 2

[0189]

[0190] From the test results in Table 1 and Table 2, it can be seen that, in the comparison between Example 1 and Comparative Example 3, the cobalt-free nickel hydroxide positive electrode material contains only the compound of Formula 1 and does not contain a conductive agent, the battery gram capacity is low, and the cycle performance is poor; in the comparison between Example 1 and Comparative Example 2, the conductive agent used in Comparative Example 2 is carbon black, and the porosity is less than 50%, the battery gram capacity is low, and the cycle performance is poor; in the comparison between Example 1, 6, 7 and Comparative Example 1, x1 and y1 do not satisfy 0≤x1≤0.1 and 0≤y1≤0.05, although the battery gram capacity is improved, the cycle life of the battery is still poor, which shows that the compound of Formula 1 and the conductive agent with a porosity greater than 50% provided in the present application synergistically enable the electrode to form a complete and interconnected conductive network while maintaining good electrolyte infiltration, realize efficient utilization of the positive active material, and significantly improve the battery gram capacity and cycle life.

[0191] Comparing Example 1-4 and Example 8-9, the rotation speed and the ball milling time are changed, and although the particle size of the expanded graphite in Example 8 and 9 is in the range of 5-100 microns, the battery capacity and cycle life are low, which shows that a does not satisfy 0.15≤a≤2, and a continuous and interconnected conductive network structure cannot be formed between the active material and the expanded graphite, the electrode cannot form a complete conductive network structure, and the conductivity of the electrode is reduced; the active material cannot fully participate in the reaction, ion diffusion is hindered, polarization increases, and the cycle life of the battery is reduced. Comparing Example 1-4 and Example 10-11, the ball milling and rotation speed are changed, and the particle size of the expanded graphite obtained is in the range of 5-100 microns, but the value of b obtained according to the formula is not in the range of 15-23.4, and the battery capacity and cycle life are poor. It is speculated that if b is too small, the excess expanded graphite fills the electrode pores, hindering ion transport; if b is too large, the content of expanded graphite is small, and the active material forms a dead zone because it is not connected to the conductive network; also reducing the cycle life of the battery; it shows that using the formula or formula to calculate, the ratio of the mass of the active material to the mass of the expanded graphite b satisfies the condition of 15≤b≤23.4, which is beneficial to the formation of a continuous conductive network between the active material and the conductive agent, so that the electrode forms a complete and interconnected conductive network, thereby realizing the efficient utilization of the positive active material and significantly improving the battery capacity and cycle life. Comparing Example 1-4 and Example 12, 5 shows that whether the values of a and b are obtained according to the formula of a and b, or the value of b is defined, they cannot match the particle size of the expanded graphite actually added and the particle size of the active material, so that the two can be better mixed and uniform, which may affect the integrity of the conductive network, thereby reducing the cycle life of the battery, which shows that the particle size of the expanded graphite is in the range of 5-100 microns, and the particle size of the active material is in the range of 5-50 microns. By calculating the values of a and b through the relationship defined in the present application, a satisfies 0.15≤a≤2, and b satisfies 15≤b≤23.4, and the battery obtained has high energy density and good cycle performance.

[0192] Comparing Example 1 and Example 13, Example 13 uses natural graphite, although the porosity of natural graphite is greater than 50%, but the energy density of the battery is low, and the cycle life is low, which shows that the reasonable composition of the compound represented by Chemical Formula 1 and the expanded graphite conductive agent in the present application can form a complete and interconnected conductive network for the electrode under the condition of maintaining good electrolyte infiltration, thereby realizing the efficient utilization of the positive active material and significantly improving the battery capacity and cycle life.

[0193] The above examples are only used to illustrate the technical solutions of the present application, but not to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those skilled in the art that the technical solutions recorded in the foregoing embodiments can be modified, or some technical features can be replaced by equivalent features. The modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. A cobalt-free nickel hydroxide cathode material, characterized in that, It includes an active substance and a conductive agent, wherein the active substance is a compound shown in chemical formula 1; Ni （1-x1-y1） Zn x1 X y1 (OH)₂, chemical formula 1; Where 0≤x1≤0.1, 0≤y1≤0.05, and X is selected from one or more of Y, Mg, Ti, and Yb; The conductive agent is selected from expanded graphite, and the particle size range of the expanded graphite is 5~100μm; the particle size of the active material is 5~50μm. The ratio of the D50 particle size D1 of the active material to the D50 particle size D2 of the expanded graphite is a, where a = D1 / D2. The expanded graphite includes one or more particle size ranges among 5~20μm, 20~40μm, 40~60μm, 60~80μm, and 80~100μm. The D50 particle size of the i-th particle size range is denoted as di, and the mass ratio of the i-th particle size range in the expanded graphite is denoted as fi, where i≥2. D2= 0.15 ≤ a ≤ 2; The expanded graphite has a porosity of 80-95% and a specific surface area of ​​50-150 m². 2 / g.

2. The cobalt-free nickel hydroxide cathode material according to claim 1, characterized in that, The ratio of the mass of the active material to the mass of the expanded graphite is b; When the particle size of the expanded graphite is selected from one or both of 5~20μm and 20~40μm, b satisfies Equation 1. Formula 1; When the particle size of the expanded graphite is selected from at least one of 40~60μm, 60~80μm, and 80~100μm, or when the particle size of the expanded graphite is selected from at least one of 5~20μm and 20~40μm and at least one of 40~60μm, 60~80μm, and 80~100μm, b satisfies Equation 2. Formula 2; Electrode porosity is 20~40%; 15≤b≤23.4。 3. A method for preparing the cobalt-free nickel hydroxide cathode material according to any one of claims 1 to 2, characterized in that, Includes the following steps: Preparation of active substances: A solution A is obtained, which contains elements X, Ni, and Zn, where X is selected from one or more of Y, Mg, Ti, and Yb. A solution B is obtained, wherein solution B is an alkaline solution; The solutions A and B are mixed and reacted. After the reaction is completed, the active substance of the compound shown in chemical formula 1 is obtained by purification. A conductive agent is obtained, and the active material is mixed with the conductive agent to obtain the cobalt-free nickel hydroxide cathode material.

4. The method for preparing the cobalt-free nickel hydroxide cathode material according to claim 3, characterized in that, The process of obtaining solution A includes the following steps: A solution A is obtained by mixing a water-soluble metal salt containing X, a water-soluble metal salt containing Ni, and a water-soluble metal salt containing Zn in a molar ratio of y1:(1-x1-y1):x1 with water, wherein the molar concentration of solution A is 1~5 mol / L. The process of obtaining solution B includes the following steps: Solution B is obtained by mixing a caustic alkali and a complexing agent, wherein the concentration of the caustic alkali is 0.5~3 mol / L and the concentration of the complexing agent is 0.2~1 mol / L.

5. The method for preparing the cobalt-free nickel hydroxide cathode material according to claim 3, characterized in that, The process of mixing and reacting solutions A and B, followed by purification after the reaction to obtain the active substance of the compound represented by chemical formula 1, includes the following steps. Mix the solutions A and B by stirring, adjust the pH to 8-11, and react at 50-80°C for 8-12 hours. After the reaction is complete, let the mixture stand for 8-24 hours. After standing, the solid substance is obtained by filtration and washing. The solid substance is dried at 60~100℃ for 8~24h to obtain solid powder. The solid powder is calcined at 200~500℃ for 3~5h. After calcination, it is pulverized to obtain the active substance of the compound shown in chemical formula 1.

6. A positive electrode plate, characterized in that, The cathode material is a cobalt-free nickel hydroxide cathode material as described in any one of claims 1-2 or prepared by the preparation method of the cobalt-free nickel hydroxide cathode material as described in any one of claims 3-5.

7. A nickel-metal hydride battery, characterized in that, It includes the negative electrode and the positive electrode as described in claim 6.

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