Sodium-ion positive electrode material precursor and preparation method thereof, sodium-ion battery positive electrode material, sodium-ion battery and electric equipment

Abstract

The invention relates to the field of sodium ion battery positive electrode materials, and discloses a sodium ion battery positive electrode material precursor and a preparation method thereof, a sodium ion battery positive electrode material, a sodium ion battery and electric equipment. The precursor contains secondary particles formed by primary particles; the porosity of the secondary particles is 20%-40%; the specific surface area of the precursor is 80-130 m < 2 > / g; the chemical general formula of the precursor is Ni < x > Fe < y > Mn < z > M < 1-x-y-z > (OH) < 2 >; wherein 0 < xlt; 0 1t, 0.4, 0 1t; y is less than or equal to 0.4, 0lt; zlt, zlt; 1, 0lt; (1-x-y-zlt); 0.5 part; m is selected from at least one of Cu, Zn, Mg, Ca, Al and Ti. The positive electrode material precursor provided by the invention is applied to the sodium-ion battery, and the obtained sodium-ion battery has high capacity at the same time.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium-ion batteries, and particularly to a precursor of a sodium-ion battery cathode material, a preparation method thereof, a sodium-ion battery cathode material, a sodium-ion battery, and an electricity-related device. Background Art

[0002] Sodium-ion batteries not only have rich raw materials and low costs, but also have characteristics such as cold resistance at low temperatures, safety and convenience, and are expected to develop rapidly in multiple fields such as low-speed electric vehicles, electric boats, household energy storage or industrial energy storage, 5G communication base stations, data centers, large-scale access of renewable energy, and smart grids.

[0003] The performance of sodium-ion batteries such as cycle stability and capacity mainly depends on the preparation of the cathode material, and the performance of the cathode material largely depends on the performance of the precursor material. Precursor materials with different morphological structures have a great influence on the cathode material and will affect the electrochemical performance of the final material.

[0004] The current cathode material precursors limit the improvement of the overall capacity and cycle stability of sodium-ion batteries. Summary of the Invention

[0005] The purpose of the present invention is to provide a precursor of a sodium-ion battery cathode material, a preparation method thereof, a sodium-ion battery cathode material, a sodium-ion battery, and an electricity-related device, aiming to solve at least one of the above technical problems in the prior art.

[0006] To achieve the above purpose, in the first aspect of the present invention, a precursor of a sodium-ion battery cathode material is provided. The precursor contains secondary particles composed of primary particles; the porosity of the secondary particles is 20%-40%; the specific surface area of the precursor is 80-130m 2 / g;

[0007] The chemical general formula of the precursor is Ni x Fe y Mn z M 1-x-y-z (OH) 2 ; wherein, 0 < x < 0.4, 0 < y ≤ 0.4, 0 < z < 1, 0 < 1 - x - y - z < 0.5; M is selected from at least one of Cu, Zn, Mg, Ca, and Al.

[0008] According to a preferred embodiment, the secondary particles include a core layer and a shell layer covering the core layer, and the precursor satisfies at least one of the following conditions:

[0009] (1) The porosity of the core layer is 20%-50%;

[0010] (2) The porosity of the shell layer is 20%-32%;

[0011] (3) The primary particles of the secondary particle shell are arranged radially along the radial direction of the secondary particle;

[0012] (4) The primary particles in the secondary particle core layer are arranged in a disordered manner.

[0013] Optionally, the particle size distribution of the precursor is (D90-D10) / D50 is 0.6-0.9.

[0014] Optionally, the D50 value of the precursor is 5-10 μm.

[0015] Optionally, the tap density of the precursor is 1.0-1.4 g / cm 3 .

[0016] According to another preferred embodiment, the surface of the precursor includes large-sized primary particles with a width greater than or equal to 0.06 μm and small-sized primary particles with a width less than 0.06 μm, and the precursor satisfies at least one of the following conditions:

[0017] ① The average width of the large-sized primary particles is 0.07-0.14 μm;

[0018] ② The average width of the small-sized primary particles is 0.015-0.05 μm;

[0019] ③ The aspect ratio of the large-sized primary particles is 5-12;

[0020] ④ The aspect ratio of the small-sized primary particles is 6-13.

[0021] The second aspect of the present invention provides a method for preparing the precursor according to the first aspect, the method comprising the following steps:

[0022] In the presence of an inert gas, a metal salt solution, a complexing agent and a precipitant are added simultaneously to a base solution having a pH value of 11.5-11.8 to perform a coprecipitation reaction;

[0023] The flow rate of the precipitant is controlled so that the pH value of the reaction system is reduced to 10.0-10.4 to obtain a coprecipitation product, and the coprecipitation product is post-treated to obtain the precursor.

[0024] According to a preferred embodiment, the method satisfies at least one of the following conditions:

[0025] A. The metal salt solution includes Ni, Fe, and Mn elements;

[0026] Optionally, the metal salt solution further comprises at least one of the elements Cu, Zn, Mg, Ca, Al, and Ti;

[0027] B. the complexing agent is selected from at least one of ammonia water, oxalic acid, EDTA, sodium sulfite and sodium acetate;

[0028] C. the precipitant is sodium hydroxide;

[0029] D. The concentration of the complexing agent is 60-80 g / L; the concentration of the precipitating agent is 20-35 wt%;

[0030] E. The metal salt solution includes at least one of a hydrochloride solution, a sulfate solution, and a nitrate solution of the metal element; the sum of the concentrations of the metal elements in the metal salt solution is 100-120 g / L;

[0031] F. The pH value reduction of the reaction system includes a decline period I and a decline period II, and the maintenance time of the decline period I is 4-8 hours.

[0032] According to a preferred embodiment, the method satisfies at least one of the following conditions:

[0033] a. The metal salt solution further comprises sulfuric acid, wherein the concentration of sulfuric acid in the metal salt solution is 0.01-0.1 mol / L;

[0034] b. The complexing agent further comprises ammonium sulfate, wherein the concentration of ammonium sulfate in the complexing agent is 0.2-0.25 mol / L;

[0035] c. The coprecipitation reaction conditions include: a reaction temperature of 40-60°C and a stirring speed of 600-1000rpm;

[0036] d. The pH value reduction rates in the decline period I and the decline period II are each independently 0.05-0.10 / h.

[0037] A third aspect of the present invention provides a sodium ion battery positive electrode material, wherein the raw material of the sodium ion battery positive electrode material includes the sodium ion positive electrode material precursor as described in the first aspect.

[0038] A fourth aspect of the present invention provides a sodium ion battery, comprising the sodium ion battery positive electrode material as described in the third aspect.

[0039] The fifth aspect of the present invention provides an electrical device, comprising the sodium ion battery as described in the fourth aspect.

[0040] Compared with the prior art, the technical solution provided by the present invention has at least the following advantages:

[0041] The secondary particles in the sodium ion positive electrode material precursor provided by the present invention have a high porosity (20%-35%) and a large specific surface area (80-130m 2 / g), the loose internal structure and large specific surface area make the open pores connecting the interior of the precursor with the surface more, which is conducive to full contact with the electrolyte, thereby improving the sodium ion transmission rate and being more conducive to the use of capacity.

[0042] The sodium ion positive electrode material precursor provided by the present invention is applied to a sodium ion battery, and the obtained sodium ion battery has a high capacity.

[0043] The preparation method of the sodium ion positive electrode material precursor provided by the present invention is simple, highly operable, and is conducive to large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 is a scanning electron microscope image of a cross section of a sodium ion positive electrode material precursor prepared in Example 1 of the present invention;

[0045] Figure 2 is a scanning electron microscope image of a local surface of the sodium ion positive electrode material precursor prepared in Example 1 of the present invention;

[0046] Figure 3 is a scanning electron microscope image of a cross section of a sodium ion positive electrode material precursor prepared in Example 3 of the present invention;

[0047] Figure 4 is a scanning electron microscope image of a local surface of the sodium ion positive electrode material precursor prepared in Example 3 of the present invention;

[0048] Figure 5 A scanning electron microscope image of a cross section of a sodium ion positive electrode material precursor prepared in Comparative Example 2 of the present invention. DETAILED DESCRIPTION

[0049] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0050] It should be noted that the porosity involved in the present invention is cross-sectional porosity, and the calculation method of cross-sectional porosity is as follows:

[0051] Adjust the magnification of the scanning electron microscope (SEM) until a cross-sectional image of a secondary particle in a single complete cathode material precursor appears in the view, take a photo to obtain the SEM image, and identify the areas of the pores in each layer (core layer and shell layer) in the cross-section of the secondary particle in the SEM through artificial intelligence (the software will identify the dark areas in the electron microscope image that have a significant color difference from the surrounding area).

[0052] Calculation formula: Cross-sectional porosity = {(total area of pores in each layer identified / total cross-sectional area of the secondary particle) × 100} (%).

[0053] Exemplarily, the magnification of the SEM photo can be 1K, 3K, 5K, 9.0K, 10.0K, 20.0K, 25.0K, 30.0K, 50.0K, etc. Specifically, the magnification is preferably such that there is only one complete or nearly complete cross-sectional image of a single secondary particle sphere in the SEM field of view.

[0054] In the present invention, the average length and average width of the primary particles on the surface of the precursor are obtained by taking multiple primary particles in the SEM image and calculating the average width or length of these multiple primary particles. Among them, the width of a single primary particle is the longest straight-line distance between any two points on the primary particle; the length is the longest straight-line distance perpendicular to the width direction of the primary particle; the aspect ratio is calculated by average length / average width.

[0055] As mentioned above, the first aspect of the present invention provides a cathode material precursor for a sodium-ion battery. The precursor contains secondary particles composed of primary particles; the porosity of the secondary particles is 20% - 40%, for example, it can be 20%, 25%, 30%, 35%, 40% or any value between 20% - 40%; the specific surface area of the precursor is 80 - 130 m 2 / g, for example, it can be 80 m 2 / g, 90 m 2 / g, 100 m 2 / g, 110 m 2 / g, 120 m 2 / g, 130 m 2 / g or any value between 80 - 130 m 2 / g;

[0056] The chemical general formula of the precursor is Ni x Fe y Mn z M 1-x-y-z (OH) 2 ; where 0 < x < 0.4, 0 < y ≤ 0.4, 0 < z < 1, 0 < 1 - x - y - z < 0.5; M is selected from at least one of Cu, Zn, Mg, Ca, Al, Ti.

[0057] By controlling the high porosity of the secondary particles in the sodium ion positive electrode material precursor and the large specific surface area of ​​the precursor, the loose internal structure and the large specific surface area make the open pores connecting the inside and the surface of the precursor more, which is conducive to sufficient contact with the electrolyte, thereby improving the transmission rate of sodium ions and being more conducive to the use of the capacity of the sodium ion battery.

[0058] In some embodiments, the secondary particle includes a core layer and a shell layer covering the core layer.

[0059] In some embodiments, the porosity of the core layer is 20%-50%, for example, it can be 20%, 25%, 30%, 35%, 40%, 45%, 50% or any value between 20%-50%;

[0060] In some embodiments, the porosity of the shell layer is 20%-32%, for example, it can be 20%, 25%, 30%, 32% or any value between 20%-32%;

[0061] In some embodiments of the present invention, the porosity of the core layer and the shell layer of the secondary particles is within the above range, which ensures sufficient contact between the corresponding sodium ion battery positive electrode material and the electrolyte, and can further improve the capacity of the corresponding sodium ion battery.

[0062] In some embodiments, the primary particles of the secondary particle shell are radially arranged along the radial direction of the secondary particle; the radially arranged structure can shorten the ion channel, which is beneficial to improving the charge and discharge capacity of the corresponding sodium ion battery.

[0063] In some embodiments, the primary particles of the secondary particle core layer are arranged in a disordered manner.

[0064] In some embodiments, the particle size distribution (D90-D10) / D50 of the precursor is 0.6-0.9, for example, it can be 0.6, 0.7, 0.8, 0.9 or any value between 0.6-0.9;

[0065] In some embodiments of the present invention, the particle size distribution of the sodium ion positive electrode material precursor is within the above range, which increases the tap density of the precursor and further increases the volume energy density of the corresponding sodium ion battery.

[0066] In some embodiments, the D50 value of the precursor is 5-10 μm, for example, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 9 μm, 10 μm or any value between 5-10 μm.

[0067] In some embodiments, the tap density of the precursor is 1.0-1.4 g / cm3 , for example, it can be 1.00 g / cm 3 , 1.05g / cm 3 , 1.10g / cm 3 , 1.15g / cm 3 , 1.20g / cm 3 , 1.25g / cm 3 , 1.30g / cm 3 , 1.35g / cm 3 , 1.40g / cm 3 or 1.0-1.4g / cm 3 Any value in between.

[0068] In some embodiments, the precursor surface includes large-sized primary particles having a width greater than or equal to 0.06 μm and small-sized primary particles having a width less than 0.06 μm.

[0069] In some embodiments, the average width of the large-sized primary particles is 0.07-0.14 μm, for example, 0.07 μm, 0.08 μm, 0.09 μm, 0.10 μm, 0.11 μm, 0.12 μm, 0.13 μm, 0.14 μm, or any value between 0.07-0.14 μm;

[0070] In some embodiments, the average width of the small-sized primary particles is 0.015-0.05 μm, for example, 0.015 μm, 0.018 μm, 0.019 μm, 0.02 μm, 0.03 μm, 0.04 μm, 0.05 μm, or any value between 0.015-0.05 μm.

[0071] In some embodiments, the aspect ratio of the large-sized primary particles is 5-12, for example, it can be 5, 6, 7, 8, 9, 10, 11, 12 or any value between 5-12.

[0072] In some embodiments, the aspect ratio of the small-sized primary particles is 6-13, for example, 6, 7, 8, 9, 10, 11, 12, 13 or any value between 6-13.

[0073] As mentioned above, the second aspect of the present invention provides a method for preparing the precursor according to the first aspect, the method comprising the following steps:

[0074] In the presence of an inert gas, a metal salt solution, a complexing agent and a precipitant are added simultaneously to a base solution having a pH value of 11.5-11.8 to perform a coprecipitation reaction;

[0075] The flow rate of the precipitant is controlled so that the pH value of the reaction system is reduced to 10.0-10.4 to obtain a coprecipitation product, and the coprecipitation product is post-treated to obtain the precursor.

[0076] In some embodiments, the inert gas comprises nitrogen.

[0077] In some embodiments, the metal salt solution includes Ni, Fe, and Mn elements;

[0078] Optionally, the metal salt solution further includes at least one of the elements Cu, Zn, Mg, Ca, Al, and Ti.

[0079] In some embodiments, the complexing agent is selected from at least one of ammonia water, oxalic acid, EDTA, sodium sulfite, and sodium acetate.

[0080] In some embodiments, the precipitating agent is sodium hydroxide;

[0081] In some embodiments, the concentration of the complexing agent is 60-80 g / L, for example, it can be 60 g / L, 70 g / L, 80 g / L or any value between 60-80 g / L; the concentration of the precipitant is 20-35 wt%, for example, it can be 20 wt%, 25 wt%, 30 wt%, 35 wt% or any value between 20-35 wt%.

[0082] In some embodiments, the metal salt solution includes at least one of a hydrochloride solution, a sulfate solution, and a nitrate solution of the metal element; the sum of the concentrations of the metal elements in the metal salt solution is 100-120 g / L, for example, it can be 100 g / L, 110 g / L, 120 g / L or any value between 100-120 g / L.

[0083] In some embodiments, the pH reduction of the reaction system includes a decline period I and a decline period II, and the maintenance time of the decline period I is 4-8 hours, for example, it can be 4 hours, 5 hours, 6 hours, 7 hours, 8 hours or any value between 4-8 hours.

[0084] In some embodiments, the metal salt solution also includes sulfuric acid, and the concentration of sulfuric acid in the metal salt solution is 0.01-0.1 mol / L, for example, it can be 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, 0.06 mol / L, 0.07 mol / L, 0.08 mol / L, 0.09 mol / L, 0.10 mol / L or any value between 0.01-0.1 mol / L.

[0085] In some embodiments, the complexing agent further includes ammonium sulfate, and the concentration of ammonium sulfate in the complexing agent is 0.2-0.25 mol / L, for example, it can be 0.2 mol / L, 0.22 mol / L, 0.24 mol / L, 0.25 mol / L or any value between 0.2-0.25 mol / L.

[0086] In some embodiments, the conditions of the coprecipitation reaction include: a reaction temperature of 40-60°C, for example, 40°C, 50°C, 60°C, or any value between 40-60°C; a stirring speed of 600-1000rpm, for example, 600rpm, 700rpm, 800rpm, 900rpm, 1000rpm, or any value between 600-1000rpm;

[0087] In some embodiments, the pH value reduction rate in the decline period I and the decline period II is independently 0.05-0.10 / h, for example, it can be 0.05 / h, 0.06 / h, 0.07 / h, 0.08 / h, 0.09 / h, 0.10 / h or any value between 0.05-0.10 / h.

[0088] By controlling the decreasing rates of the pH values ​​in the decreasing period I and the decreasing period II respectively, the morphology, size and porosity of the primary particles of the core layer and the shell layer can be controlled, thereby regulating various parameters of the precursor within an appropriate range.

[0089] The present invention has no particular requirements for the post-treatment method, and those skilled in the art can select it according to known technical means. For example, the post-treatment includes washing, centrifugation, sieving, etc., which will not be described in detail in the present invention, and those skilled in the art should not be construed as limiting the present invention.

[0090] As mentioned above, the third aspect of the present invention provides a sodium ion battery positive electrode material, and the raw material of the sodium ion battery positive electrode material includes the sodium ion positive electrode material precursor as described in the first aspect.

[0091] The present invention has no particular restrictions on the method for preparing a sodium ion battery positive electrode material using the sodium ion positive electrode material precursor provided by the present invention, and those skilled in the art can select it according to technical means known in the art. However, in order to obtain a sodium ion battery positive electrode material with better electrochemical performance, the present invention preferably uses the following method to prepare the sodium ion battery positive electrode material.

[0092] According to a preferred specific embodiment, the method for preparing the positive electrode material of a sodium ion battery comprises:

[0093] In the presence of an oxygen-containing atmosphere, the sodium ion positive electrode material precursor is mixed with a sodium source in a molar ratio of 1:1.01-1.03, and then sintered to obtain the sodium ion battery positive electrode material.

[0094] In some embodiments, the sintering conditions include: heating to 800-1000°C at a heating rate of 1-2°C / min, for example, 800, 850, 900°C, 1000°C or any value between 800-1000°C; sintering time is 10-15h, for example, 10h, 11h, 12h, 13h, 14h, 15h or any value between 10-15h.

[0095] In the present invention, the sintering time includes the time required for heating.

[0096] In some embodiments, the oxygen-containing atmosphere is air.

[0097] The preparation method of the sodium ion battery positive electrode material of the present invention may also include cooling, crushing, and other post-processing means known in the art to obtain the sodium ion battery positive electrode material with better quality. The present invention will not be repeated here, and those skilled in the art should not be understood as limiting the present invention.

[0098] As mentioned above, the fourth aspect of the present invention provides a sodium ion battery, comprising the sodium ion battery positive electrode material as described in the third aspect.

[0099] As mentioned above, the fifth aspect of the present invention provides an electrical device, including the sodium ion battery described in the fourth aspect.

[0100] The present invention will be described in detail below by way of examples. In the following examples, unless otherwise specified, the raw materials are all commercially available.

[0101] Precipitant: sodium hydroxide solution, mass fraction is 25wt%.

[0102] Example 1

[0103] Prepare a chemical formula Ni 0.22 Fe 0.33 Mn 0.34 Cu 0.11 (OH) 2 The specific preparation method of the sodium ion positive electrode material precursor is as follows:

[0104] ① Dissolve nickel sulfate, ferrous sulfate, manganese sulfate, and copper sulfate crystals into a metal salt solution with a nickel ion concentration of 26.5 g / L, a ferrous ion concentration of 37.8 g / L, a manganese ion concentration of 37.3 g / L, and a copper ion concentration of 14.3 g / L. The metal salt solution contains sulfuric acid, and the concentration of sulfuric acid in the metal salt solution is 0.05 mol / L;

[0105] Prepare a sodium acetate solution with a concentration of 78±2g / L, the sodium acetate solution contains ammonium sulfate, and the concentration of ammonium sulfate in the sodium acetate solution is 0.2mol / L;

[0106] ② In the presence of nitrogen, pure water, sodium acetate crystals, ammonium sulfate crystals, and sodium hydroxide solution were added to the reaction kettle to obtain a bottom liquid, so that the pH value of the bottom liquid was between 11.50 and 11.60;

[0107] ③ The reactor was heated to 50°C, the stirring speed was controlled at 800 rpm, and the metal salt solution, sodium acetate solution and sodium hydroxide solution were added to the bottom liquid at 8% / h, 0.8% / h and 3.2% / h of the total volume of the reactor, respectively, to control the actual pH value of the reaction process, so that the pH value was reduced to 10.20 to obtain a coprecipitated product; wherein, the pH value reduction rate in the first 8 hours of the reaction was 0.1 / h (decline period I), which was conducive to the formation of a network core, and the pH value reduction range after 8 hours became 0.05 / h (decline period II), which was conducive to slowing down the growth rate and thickening the primary particles;

[0108] The coprecipitated product is sequentially washed with pure water and centrifuged, and the centrifuged material is dried and sieved to obtain a sodium ion positive electrode material precursor.

[0109] Figure 1 , Figure 2 They are respectively a scanning electron microscope image of a cross section of a sodium ion positive electrode material precursor prepared in this embodiment and a scanning electron microscope image of a local surface of the precursor;

[0110] pass Figure 1 It can be seen that the primary particles of the shell layer of the secondary particle of the precursor are arranged radially along the radial direction of the secondary particle, and the primary particles of the core layer of the secondary particle of the precursor are arranged disorderly;

[0111] pass Figure 2 The average length and average width of the primary particles on the surface of the sodium ion cathode material precursor can be obtained. The specific method is as follows: measure Figure 2The length and width of the 20 primary particles were calculated, and the average length and width of all primary particles with a width greater than or equal to 0.06 μm were calculated, thereby concluding that the average width of the large-sized primary particles was 0.097 μm, the average length was 0.889 μm, and the aspect ratio was 9.16; the average length and width of all primary particles with a width less than 0.06 μm were calculated, thereby concluding that the average width of the small-sized primary particles was 0.04 μm, the average length was 0.383 μm, and the aspect ratio was 9.58.

[0112] Example 2

[0113] Prepare a chemical formula Ni 0.23 Fe 0.33 Mn 0.38 Zn 0.06 (OH) 2 The specific preparation method of the sodium ion positive electrode material precursor is as follows:

[0114] ① Dissolve nickel sulfate, ferrous sulfate, manganese sulfate and zinc sulfate crystals into a metal salt solution with a nickel ion concentration of 27.6 g / L, a ferrous ion concentration of 42.7 g / L, a manganese ion concentration of 37.7 g / L and a zinc ion concentration of 8.0 g / L. The metal salt solution contains sulfuric acid, and the concentration of sulfuric acid in the metal salt solution is 0.05 mol / L;

[0115] Prepare a sodium acetate solution with a concentration of 78±2g / L, the sodium acetate solution contains ammonium sulfate, and the concentration of ammonium sulfate in the sodium acetate solution is 0.2mol / L;

[0116] ② In the presence of nitrogen, pure water, sodium acetate crystals, ammonium sulfate crystals, and sodium hydroxide solution were added to the reaction kettle to obtain a bottom liquid, so that the pH value of the bottom liquid was between 11.70 and 11.80;

[0117] ③ The reactor was heated to 50°C, the stirring speed was controlled at 800 rpm, and the metal salt solution, sodium acetate solution and sodium hydroxide solution were added to the bottom liquid at 8% / h, 0.8% / h and 3.2% / h of the total volume of the reactor, respectively, to control the actual pH value of the reaction process so that the pH value was successively reduced to 10.20 to obtain a coprecipitated product; wherein, the pH value reduction rate in the first 8 hours of the reaction was 0.08 / h (decline period I), and the pH reduction amplitude became 0.05 / h after 8 hours (decline period II);

[0118] The coprecipitated product is sequentially washed with pure water and centrifuged, and the centrifuged material is dried and sieved to obtain a sodium ion positive electrode material precursor.

[0119] Example 3

[0120] Prepare a chemical formula Ni0.22 Fe 0.25 Mn 0.42 Cu 0.11 (OH) 2 The specific preparation method of the sodium ion positive electrode material precursor is as follows:

[0121] ① Dissolve nickel sulfate, ferrous sulfate, manganese sulfate, and copper sulfate crystals into a metal salt solution with a nickel ion concentration of 26.5 g / L, a ferrous ion concentration of 37.8 g / L, a manganese ion concentration of 37.3 g / L, and a copper ion concentration of 14.3 g / L. The metal salt solution contains sulfuric acid, and the concentration of sulfuric acid in the metal salt solution is 0.05 mol / L;

[0122] Prepare a sodium acetate solution with a concentration of 78±2g / L, the sodium acetate solution contains ammonium sulfate, and the concentration of ammonium sulfate in the sodium acetate solution is 0.2mol / L;

[0123] ② In the presence of nitrogen, pure water, sodium acetate crystals, ammonium sulfate crystals, and sodium hydroxide solution were added to the reaction kettle to obtain a bottom liquid, so that the pH value of the bottom liquid was between 11.70 and 11.80;

[0124] ③ The reactor was heated to 50°C, the stirring speed was controlled at 800 rpm, and the metal salt solution (8% / h of the total volume of the reactor), the sodium acetate solution (0.8% / h of the total volume of the reactor) and the sodium hydroxide solution (3.2% / h of the total volume of the reactor) were added to the bottom liquid at the same time, and the actual pH value of the reaction process was controlled to reduce the pH value to 10.20 to obtain a coprecipitated product; wherein, the pH value reduction rate in the first 8 hours of the reaction was 0.08 / h (decline period I), and the pH reduction amplitude became 0.05 / h after 8 hours (decline period II);

[0125] The coprecipitated product is sequentially washed with pure water and centrifuged, and the centrifuged material is dried and sieved to obtain a sodium ion positive electrode material precursor.

[0126] Figure 3 , Figure 4 They are respectively a scanning electron microscope image of a cross section of a sodium ion positive electrode material precursor prepared in this embodiment and a scanning electron microscope image of a local surface of the precursor;

[0127] pass Figure 3 It can be seen that the primary particles of the shell layer of the secondary particle of the precursor are arranged radially along the radial direction of the secondary particle, and the primary particles of the core layer of the secondary particle of the precursor are arranged disorderly;

[0128] pass Figure 4It can be concluded that the average width of the large-sized primary particles on the surface of the sodium ion positive electrode material precursor is 0.087 μm, the average length is 0.831 μm, and the aspect ratio is 9.55; the average width of the small-sized primary particles is 0.038 μm, the average length is 0.473 μm, and the aspect ratio is 12.45. The method is the same as in Example 1 and will not be repeated here.

[0129] Example 4

[0130] Prepare a chemical formula Ni 0.22 Fe 0.33 Mn 0.34 Cu 0.11 (OH) 2 The specific preparation method of the sodium ion positive electrode material precursor is as follows:

[0131] ① Dissolve nickel sulfate, ferrous sulfate, manganese sulfate, and copper sulfate crystals into a metal salt solution with a nickel ion concentration of 26.5±2g / L, an iron ion concentration of 37.8g / L, a manganese ion concentration of 37.3±2g / L, and a copper ion concentration of 14.3±2g / L. The metal salt solution contains sulfuric acid, and the concentration of sulfuric acid in the metal salt solution is 0.05mol / L;

[0132] Prepare a sodium acetate solution with a concentration of 78±2g / L, the sodium acetate solution contains ammonium sulfate, and the concentration of ammonium sulfate in the sodium acetate solution is 0.2mol / L;

[0133] ② In the presence of nitrogen, pure water, sodium acetate crystals, ammonium sulfate crystals, and sodium hydroxide solution were added to the reaction kettle to obtain a bottom liquid, so that the pH value of the bottom liquid was between 11.70 and 11.80;

[0134] ③ The reactor was heated to 50°C, the stirring speed was controlled at 800 rpm, and a metal salt solution (8% / h of the total volume of the reactor), a sodium acetate solution (0.8% / h of the total volume of the reactor) and a sodium hydroxide solution (3.2% / h of the total volume of the reactor) were added to the bottom liquid at the same time, and the actual pH value of the reaction process was controlled to reduce the pH value to 10.20 to obtain a coprecipitated product; wherein, the pH value reduction rate in the first 8 hours of the reaction was 0.05 / h (decline period I), and the pH reduction amplitude became 0.1 / h after 8 hours (decline period II);

[0135] The coprecipitated product is sequentially washed with pure water and centrifuged, and the centrifuged material is dried and sieved to obtain a sodium ion positive electrode material precursor.

[0136] Example 5

[0137] Prepare a chemical formula Ni 0.22 Fe 0.33 Mn 0.34 Cu0.11 (OH) 2 The specific preparation method of the sodium ion positive electrode material precursor is as follows:

[0138] ① Dissolve nickel sulfate, ferrous sulfate, manganese sulfate, and copper sulfate crystals into a metal salt solution with a nickel ion concentration of 26.5±2g / L, an iron ion concentration of 37.8g / L, a manganese ion concentration of 37.3±2g / L, and a copper ion concentration of 14.3±2g / L. The metal salt solution contains sulfuric acid, and the concentration of sulfuric acid in the metal salt solution is 0.05mol / L;

[0139] Prepare a sodium acetate solution with a concentration of 78±2g / L, the sodium acetate solution contains ammonium sulfate, and the concentration of ammonium sulfate in the sodium acetate solution is 0.2mol / L;

[0140] ② In the presence of nitrogen, pure water, sodium acetate crystals, ammonium sulfate crystals, and sodium hydroxide solution were added to the reaction kettle to obtain a bottom liquid, so that the pH value of the bottom liquid was between 11.50 and 11.60;

[0141] ③ The reactor was heated to 50°C, the stirring speed was controlled at 800 rpm, and a metal salt solution (8% / h of the total volume of the reactor), a sodium acetate solution (0.8% / h of the total volume of the reactor) and a sodium hydroxide solution (3.2% / h of the total volume of the reactor) were added to the bottom liquid at the same time, and the actual pH value of the reaction process was controlled to reduce the pH value to 10.20 to obtain a coprecipitated product; wherein, the pH value reduction rate in the first 8 hours of the reaction was 0.05 / h (decline period I), and the pH reduction amplitude became 0.08 / h after 8 hours (decline period II);

[0142] The coprecipitated product is sequentially washed with pure water and centrifuged, and the centrifuged material is dried and sieved to obtain a sodium ion positive electrode material precursor.

[0143] Comparative Example 1

[0144] Prepare a chemical formula Ni 0.22 Fe 0.33 Mn 0.34 Cu 0.12 (OH) 2 The specific preparation method of the sodium ion positive electrode material precursor is as follows:

[0145] ① Dissolve nickel sulfate, ferrous sulfate, manganese sulfate, and copper sulfate crystals into a metal salt solution with a nickel ion concentration of 26.5 g / L, a ferrous ion concentration of 37.8 g / L, a manganese ion concentration of 37.3 g / L, and a copper ion concentration of 14.3 g / L. The metal salt solution contains sulfuric acid, and the concentration of sulfuric acid in the metal salt solution is 0.025 mol / L;

[0146] Prepare a sodium acetate solution with a concentration of 78±2g / L, the sodium acetate solution contains ammonium sulfate, and the concentration of ammonium sulfate in the sodium acetate solution is 0.1mol / L;

[0147] ② In the presence of nitrogen, pure water, sodium acetate crystals, ammonium sulfate crystals, and sodium hydroxide solution were added to the reaction kettle to obtain a bottom liquid, so that the pH value of the bottom liquid was between 11.50 and 11.60;

[0148] ③ The reactor was heated to 50°C, the stirring speed was controlled at 800 rpm, and the metal salt solution (8% / h of the total volume of the reactor), the sodium acetate solution (0.8% / h of the total volume of the reactor) and the sodium hydroxide solution (3.2% / h of the total volume of the reactor) were added to the bottom liquid at the same time, and the actual pH value of the reaction process was controlled to reduce the pH value to 10.20 to obtain a coprecipitated product; wherein, the pH value reduction rate in the first 8 hours of the reaction was 0.15 / h (decline period I), the inner core looseness increased, and the pH decrease rate slowed down by 0.1 / h after 8 hours (decline period II);

[0149] The coprecipitated product is sequentially washed with pure water and centrifuged, and the centrifuged material is dried and sieved to obtain a sodium ion positive electrode material precursor.

[0150] Comparative Example 2

[0151] Prepare a chemical formula Ni 0.22 Fe 0.33 Mn 0.34 Cu 0.11 (OH) 2 The specific preparation method of the sodium ion positive electrode material precursor is as follows:

[0152] ① Dissolve nickel sulfate, ferrous sulfate, manganese sulfate, and copper sulfate crystals into a metal salt solution with a nickel ion concentration of 26.5 g / L, a ferrous ion concentration of 37.8 g / L, a manganese ion concentration of 37.3 g / L, and a copper ion concentration of 14.3 g / L. The metal salt solution contains sulfuric acid, and the concentration of sulfuric acid in the metal salt solution is 0.025 mol / L;

[0153] Prepare a sodium acetate solution with a concentration of 78±2g / L, the sodium acetate solution contains ammonium sulfate, and the concentration of ammonium sulfate in the sodium acetate solution is 0.05mol / L;

[0154] ② In the presence of nitrogen, pure water, sodium acetate crystals, ammonium sulfate crystals, and sodium hydroxide solution were added to the reaction kettle to obtain a bottom liquid, so that the pH value of the bottom liquid was between 11.50 and 11.60;

[0155] ③ The reactor was heated to 50°C, the stirring speed was controlled at 800 rpm, and the metal salt solution (8% / h of the total volume of the reactor), the sodium acetate solution (0.8% / h of the total volume of the reactor) and the sodium hydroxide solution (3.2% / h of the total volume of the reactor) were added to the bottom liquid at the same time, and the actual pH value of the reaction process was controlled to reduce the pH value to 10.20 to obtain a coprecipitated product; wherein, the pH value reduction rate in the first 8 hours of the reaction was 0.15 / h (decline period I), and the pH decrease rate slowed down by 0.1 / h after 8 hours (decline period II);

[0156] The coprecipitated product is sequentially washed with pure water and centrifuged, and the centrifuged material is dried and sieved to obtain a sodium ion positive electrode material precursor.

[0157] Figure 5 It is a scanning electron microscope image of the cross section of the sodium ion positive electrode material precursor prepared in this comparative example.

[0158] Test Example 1

[0159] The sodium ion positive electrode material precursors prepared in the above-mentioned embodiments and comparative examples were tested for physical and chemical data, specifically:

[0160] 1. The porosity of the secondary particles in the sodium ion cathode material precursor, the core layer porosity in the secondary particles, and the shell layer porosity in the secondary particles are all measured by scanning electron microscopy combined with image recognition software;

[0161] 2. Particle size (D50) and particle size distribution (D90-D10) / D50 were tested using Malvern 3000 laser particle size analyzer, with reference to standard GB / T 19077-2016;

[0162] 3. The test reference standard for tap density (TD) is GB / T 5162-2021 Determination of tap density of metal powders;

[0163] 4. Specific surface area (BET) is determined according to GB / T 19587-2017 gas adsorption BET method for solid matter determination;

[0164] The specific results are shown in Tables 1 and 2.

[0165] Table 1

[0166]

[0167] Table 2

[0168] <![CDATA[BET(m 2 / g)]]> D50(μm) (D90-D10) / D50 <![CDATA[TD(g / cm 3 )]]> Example 1 90.68 9.196 0.85 1.31 Example 2 87.72 6.092 0.75 1.22 Example 3 111.49 5.09 0.77 1.20 Example 4 89.36 8.732 0.78 1.25 Example 5 85.23 9.056 0.81 1.22 Comparative Example 1 11.30 9.168 0.76 1.08 Comparative Example 2 119.060 9.048 0.74 1.02

[0169] Test Example 2

[0170] In the presence of an air atmosphere, the sodium ion positive electrode material precursor prepared in the above example was mixed with sodium carbonate in a molar ratio of 1:1.01, and then sintered (heating to 900°C at a heating rate of 1°C / min, sintering time 12h) to obtain a sodium ion battery positive electrode material.

[0171] Assemble the battery:

[0172] The positive electrode material was mixed with polyvinylidene fluoride and acetylene black in a mass ratio of 8:1:1, N-methyl-pyrrolidone was added, and then evenly coated on the current collector aluminum foil as the positive electrode. After drying, in the glove box, the metal sodium sheet was used as the negative electrode, 1mol / L NaClO4 solution was used as the electrolyte, and the glass fiber was used as the separator to assemble a CR2032 button battery. First, it was activated by charging and discharging at a current density of 0.1C (1C = 150mAh / g) for 2 weeks, then charged and discharged at a current density of 0.2C for 2 weeks, and finally charged and discharged at a current density of 1C for 50 weeks, with a charge cut-off voltage of 4.2V and a discharge cut-off voltage of 4.2V.

[0173] The electrochemical performance test data are shown in Table 3.

[0174] Table 3

[0175] 0.1C first charge capacity (mAh / g) First effect / % Ratio (1C / 0.1C) / % Example 1 142.2 91.40 95.15 Example 2 140.9 90.95 95.35 Example 3 143.7 91.33 95.87 Example 4 138.4 90.86 94.56 Example 5 137.8 91.03 94.91 Comparative Example 1 132.8 90.15 93.35 Comparative Example 2 133.4 90.37 93.71

[0176] From the above results, it can be seen that the specific surface area of ​​the sodium ion positive electrode material precursors of Examples 1-5 is 80-130 m 2 / g, the porosity of the secondary particles in the sodium ion positive electrode material precursor is between 20% and 40%, and the capacity of the corresponding button battery prepared is better than that of comparative examples 1-2.

[0177] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A sodium ion battery cathode material precursor, characterized in that: The precursor contains secondary particles composed of primary particles; the porosity of the secondary particles is 20%-40%; the specific surface area of ​​the precursor is 80-130m 2 / g; The chemical general formula of the precursor is Ni x Fe y Mn z M 1-x-y-z (OH)2; wherein, 0 < x < 0.4, 0 < y ≤ 0.4, 0 < z < 1, 0 < 1 - x - y - z < 0.5; M is selected from at least one of Cu, Zn, Mg, Ca, Al, and Ti.

2. The precursor according to claim 1, characterized in that The secondary particles include a core layer and a shell layer covering the core layer, and the precursor satisfies at least one of the following conditions: (1) The porosity of the core layer is 20%-50%; (2) The porosity of the shell layer is 20%-32%; (3) The primary particles of the secondary particle shell are arranged radially along the radial direction of the secondary particle; (4) The primary particles in the secondary particle core layer are arranged in a disordered manner.

3. The precursor according to claim 1 or 2, characterized in that The particle size distribution (D90-D10) / D50 of the precursor is 0.6-0.9; and / or, the D50 value of the precursor is 5-10 μm; And / or, the tap density of the precursor is 1.0-1.4 g / cm 3 .

4. The precursor according to claim 1, wherein the surface of the precursor comprises large-sized primary particles with a width greater than or equal to 0.06 μm and small-sized primary particles with a width less than 0.06 μm, characterized in that: The precursor satisfies at least one of the following conditions: ① The average width of the large-sized primary particles is 0.07-0.14 μm; ② The average width of the small-sized primary particles is 0.015-0.05 μm; ③ The aspect ratio of the large-sized primary particles is 5-12; ④ The aspect ratio of the small-sized primary particles is 6-13.

5. A method for preparing a precursor according to any one of claims 1 to 4, characterized in that: The method comprises the following steps: In the presence of an inert gas, a metal salt solution, a complexing agent and a precipitant are added simultaneously to a base solution having a pH value of 11.5-11.8 to perform a coprecipitation reaction; The flow rate of the precipitant is controlled so that the pH value of the reaction system is reduced to 10.0-10.4 to obtain a coprecipitation product, and the coprecipitation product is post-treated to obtain the precursor.

6. The method according to claim 5, characterized in that The method satisfies at least one of the following conditions: A. The metal salt solution includes Ni, Fe, and Mn elements; Optionally, the metal salt solution further comprises at least one of the elements Cu, Zn, Mg, Ca, Al, and Ti; B. the complexing agent is selected from at least one of ammonia water, oxalic acid, EDTA, sodium sulfite and sodium acetate; C. the precipitant is sodium hydroxide; D. The concentration of the complexing agent is 60-80 g / L; the concentration of the precipitating agent is 20-35 wt%; E. The metal salt solution includes at least one of a hydrochloride solution, a sulfate solution, and a nitrate solution of the metal element; the sum of the concentrations of the metal elements in the metal salt solution is 100-120 g / L; F. The pH value reduction of the reaction system includes a decline period I and a decline period II, and the maintenance time of the decline period I is 4-8 hours.

7. The method according to claim 5 or 6, characterized in that: The method satisfies at least one of the following conditions: a. The metal salt solution further comprises sulfuric acid, wherein the concentration of sulfuric acid in the metal salt solution is 0.01-0.1 mol / L; b. The complexing agent further comprises ammonium sulfate, wherein the concentration of ammonium sulfate in the complexing agent is 0.2-0.25 mol / L; c. The coprecipitation reaction conditions include: a reaction temperature of 40-60°C and a stirring speed of 600-1000rpm; d. The pH value reduction rates in the decline period I and the decline period II are each independently 0.05-0.10 / h.

8. A sodium ion battery positive electrode material, characterized in that: The raw material of the sodium ion battery positive electrode material includes the sodium ion positive electrode material precursor according to any one of claims 1 to 4.

9. A sodium ion battery, characterized in that: Comprising the sodium ion battery positive electrode material as claimed in claim 8.

10. An electrical equipment, characterized in that: Comprising the sodium ion battery as claimed in claim 9.

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