A cathode precursor material for a sodium-ion battery, a preparation method thereof, a cathode material, a sodium-ion battery, and an electrical device

Abstract

The present application provides a sodium-ion battery cathode precursor material, a preparation method thereof, a cathode material, a sodium-ion battery, and an electrical device, relating to the field of sodium-ion batteries. The vertical distance d from the fitted arc at the top of the primary particle of the sodium-ion battery cathode precursor material to the cross-section satisfies the relationship with the thickness s of the primary particle: 1 / 8 ≤ d / s ≤ 1 / 4. This sodium-ion battery cathode precursor material has few voids but is closely fitted, the primary particles are thick but stacked with stacking faults, and has better sodium-ion absorption capacity.

Description

Technical Field

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

[0002] Sodium-ion batteries (SIBs) are considered to be one of the most promising candidates to replace current commercial lithium-ion batteries due to the abundant reserves, low cost of sodium, and similar characteristics to lithium-ion batteries.

[0003] Sodium transition metal oxides (Na x TMO2; x≤1; where TM is a transition metal such as Ni, Co, Mn, Fe, Cu, Cr, etc.) are promising cathode materials for SIBs. According to the coordination environment of Na ions (prismatic or octahedral sites) and the number of TMO2 layers in the repeating stacking unit, Na layered oxides are mainly divided into P2 and O3 types; P2-type cathodes have larger Na + diffusion channels and better kinetic performance, but the Na content in P2-type cathodes is insufficient, resulting in a lower theoretical specific capacity. In addition, the harmful phase transformation from P2 to O2 at high voltage is accompanied by a significant volume change, leading to a rapid capacity decay. In contrast, the O3-phase cathode material has a high initial Na content, corresponding to a higher theoretical capacity, which requires the introduction of a large amount of sodium source in the solid-phase sintering stage. During the sintering process, Na + penetrates from the (010) plane of the precursor surface into the interior. Optimizing the (010) exposed surface of the precursor can expand the ion transport channels and reduce the residual alkali on the material surface.

[0004] The precursor is a key intermediate product connecting upstream raw material resources and downstream cathode materials in the battery industry chain. Theoretically, the crystal structure of the precursor can be inherited to the cathode material, and its physical and chemical indexes (such as element composition, particle size, tap density, specific surface area, surface morphology, crystal structure, etc.) directly affect the performance of the sintered cathode material.

[0005] For example, Chinese Patent CN115072805B reports a precursor for a sodium-ion battery cathode material composed of cross-connected sheet structures. The sodium-ion battery cathode material prepared therefrom has a high specific capacitance, first-cycle Coulombic efficiency, and cycle stability when assembled into a battery. However, the sphericity of the precursor material described therein is poor. When introducing sodium source for sintering, sodium ions tend to accumulate at the depressions on the surface of the precursor sphere, resulting in uneven inward diffusion rate of sodium ions and forming a certain sodium ion concentration gradient inside the cathode material. After long-term cycling, the cathode performance deteriorates significantly.

[0006] As disclosed in Chinese Patent CN118289841A, a sodium-ion battery cathode material with in-situ coating was reported. A low-alkali sodium source was used to replace part of sodium carbonate to reduce alkalinity and conduct in-situ doping. After a single sintering, a metal oxide was used for coating, and the coating layer could further reduce the residual alkali on the material surface. However, the introduction of multiple additives would, to a certain extent, hinder the diffusion of sodium ions, and using a multi-layer coating method to reduce residual alkali would increase production costs and was not suitable for industrialization.

[0007] Another example is Chinese Patent CN117401726A, which reported a zinc-doped sodium-ion battery cathode precursor material. By doping zinc elements to modify the material, a sodium-ion battery cathode material precursor was prepared using the coprecipitation method, which could increase the contact area with the electrolyte and improve the sodium ion transport efficiency. However, there were differences in the precipitation equilibrium constants of zinc ions, nickel ions, iron ions, and manganese ions, and simple mixed coprecipitation was prone to uneven element distribution problems.

[0008] Therefore, how to conduct modification regulation at the precursor end, guide the optimization of the cathode material crystal, and obtain a material with better comprehensive performance is an urgent problem to be solved currently. Summary of the Invention

[0009] The purpose of this application is to provide a sodium-ion battery cathode precursor material, its preparation method, cathode material, sodium-ion battery, and electrical equipment to solve the above problems.

[0010] To achieve the above purpose, in the first aspect of this application, a sodium-ion battery cathode precursor material is provided. The vertical distance d from the arc fitted at the top of the primary particle of the sodium-ion battery cathode precursor material to the cross-section and the thickness s of the primary particle satisfy the relationship:

[0011] 1 / 8 ≤ d / s ≤ 1 / 4.

[0012] Optionally, the thickness s of the primary particle is 120 nm - 360 nm.

[0013] Optionally, the thickness s of the primary particle and the gap width t between the primary particles satisfy the relationship:

[0014] 1.0 ≤ s / t ≤ 7.5.

[0015] Optionally, the gap width t between the primary particles is 45 nm - 120 nm.

[0016] Optionally, the sodium-ion battery cathode precursor material satisfies at least one of the following conditions:

[0017] A. The D50 of the sodium-ion battery cathode precursor material is 7 μm - 12 μm;

[0018] B. The tap density TD of the positive electrode precursor material of the sodium ion battery is ≥ 1.4 g / cm 3 ;

[0019] C. The specific surface area SSA of the positive electrode precursor material of the sodium ion battery is 2 m 2 / g - 5 m 2 / g;

[0020] D. The pH value of the positive electrode precursor material of the sodium ion battery is 8 - 10;

[0021] E. The content of Na + in the positive electrode precursor material of the sodium ion battery is ≤ 200 ppm, and the content of SO4 2- is ≤ 2000 ppm;

[0022] F. The mass content of water in the positive electrode precursor material of the sodium ion battery is ≤ 0.60%;

[0023] G. The positive electrode precursor material of the sodium ion battery is spherical and / or quasi-spherical;

[0024] H. The chemical formula of the positive electrode precursor material of the sodium ion battery is Ni a Fe b Mn c R (1-a-b-c) (OH)2; wherein, 0.1 ≤ a ≤ 0.4, 0 < b ≤ 0.3, 0 < c ≤ 0.7, 0.9 ≤ a + b + c ≤ 1, and R is selected from one or more of the elements Zn, Mg, Ti, Cu, Ca, W, Al, Co, Zr;

[0025] I. The positive electrode precursor material of the sodium ion battery includes an O3-type positive electrode precursor material of the sodium ion battery.

[0026] The second aspect of the present application provides a preparation method of the positive electrode precursor material of the sodium ion battery, including:

[0027] In an inert atmosphere, a mixed metal salt solution, a doped metal salt solution, a complexing agent, and a precipitating agent are introduced into a bottom liquid in a flowing manner, and a first reaction is carried out under stirring, controlling the pH value of the solution in the first reaction process to continuously decrease, and then the mixed metal salt solution, the doped metal salt solution, the complexing agent, and the precipitating agent are introduced, and the pH is maintained constant to carry out a second reaction to prepare the positive electrode precursor material of the sodium ion battery;

[0028] Among them, the mixed metal salt solution includes a manganese salt, a nickel salt, and an iron salt.

[0029] Optionally, the preparation method of the positive electrode precursor material of the sodium ion battery satisfies at least one of the following conditions:

[0030] A. The manganese salt includes one or more of manganese sulfate, manganese chloride, manganese acetate, and manganese nitrate;

[0031] B. The nickel salt includes one or more of nickel sulfate, nickel chloride, nickel acetate, and nickel nitrate;

[0032] C. The iron salt includes one or more of ferrous sulfate, ferrous chloride, ferrous acetate, and ferrous nitrate;

[0033] D. The doped metal salt in the doped metal salt solution includes one or more of sulfates, chlorides, acetates, and nitrates containing doped elements;

[0034] E. The complexing agent includes one or more of ammonia water, oxalic acid, citric acid, or sodium citrate;

[0035] F. The precipitating agent includes one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, and potassium carbonate;

[0036] G. The inert gas in the inert atmosphere includes nitrogen and / or argon;

[0037] H. The bottom liquid is a mixture of the water, the precipitating agent, and the complexing agent;

[0038] I. The pH value of the bottom liquid is 12.00 - 13.00;

[0039] J. The end point pH of the first reaction is 11.40 - 11.60, and the time is 0.5 h - 1 h;

[0040] K. The temperatures of the first reaction and the second reaction are both 55 - 65 °C;

[0041] L. The pH of the second reaction is 11.40 - 11.60.

[0042] In the third aspect of the present application, a cathode material is provided, which is obtained by mixing and sintering the sodium ion battery cathode precursor material described above with a sodium source.

[0043] In the fourth aspect of the present application, a sodium ion battery is provided, which includes the cathode material described above.

[0044] In the fifth aspect of the present application, an electrical equipment is provided, which includes the sodium ion battery described above.

[0045] Compared with the prior art, the beneficial effects of the present application include:

[0046] The sodium-ion battery cathode precursor material provided by this application has few voids but is closely attached, with thick primary particles but stacking faults (loose stacking). After introducing doping elements, stratification occurs inside the primary particles of the precursor, and more active sites are obtained on the exposed (010) crystal plane. When sintering and fusing, the surface energy of the material decreases, and it has better sodium-ion absorption performance.

[0047] The preparation method of the sodium-ion battery cathode precursor material provided by this application realizes the uniform dispersion of materials under stirring. The primary nanosheets of the precursor formed by co-building doping elements and transition metal elements under strong stirring have a uniform element distribution. Due to the introduction of doping elements with a high number of outer electrons, the number of hydrogen bonds in the transition metal layer increases, and the electrostatic repulsion is enhanced, further changing the structure of the primary particles of the precursor. The primary particles become loose and stratified inside.

[0048] The cathode material provided by this application can form a polycrystalline sodium battery cathode material with high crystallinity at a short holding time and a low sintering temperature, and has advantages such as better performance, lower residual alkali, and lower cost.

[0049] The sodium-ion battery and electrical equipment provided by this application have low cost and good performance. Description of the Drawings

[0050] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as limiting the scope of this application.

[0051] Figure 1 Schematic diagram of primary particles with loose stacked layers;

[0052] Figure 2 For Figure 1 Local enlarged view of the red line area in;

[0053] Figure 3 Schematic diagram of dense primary particles;

[0054] Figure 4 Schematic diagram for measuring the vertical distance d and thickness s on the SEM image of the O3-type sodium-ion battery cathode precursor material in Example 1;

[0055] Figure 5 Schematic diagram of the slit width t and thickness s on the SEM image of the O3-type sodium-ion battery cathode precursor material in Example 1;

[0056] Figure 6 SEM image of the O3-type sodium-ion battery cathode precursor material provided in Example 1. Detailed Embodiments

[0057] As used herein, the terms:

[0058] "Prepared by..." is synonymous with "comprising". As used herein, the terms "comprising", "including", "having", "containing" or any other variation thereof are intended to cover non-exclusive inclusion. For example, a composition, step, method, article or apparatus comprising the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article or apparatus.

[0059] The conjunctive "consisting of" excludes any unrecited element, step or component. If used in a claim, this phrase will render the claim closed, excluding materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause within the body of a claim rather than immediately following the subject, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0060] When an equivalent, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper preferred values and lower preferred values, this should be understood to specifically disclose all ranges formed by any pairing of any upper range limit or preferred value with any lower range limit or preferred value, whether or not the ranges are separately disclosed. For example, when the range "1 to 5" is disclosed, the described range should be interpreted as including the ranges "1 to 4", "1 to 3", "1 to 2", "1 to 2 and 4 to 5", "1 to 3 and 5", etc. When a numerical range is described herein, unless otherwise stated, the range is intended to include its end values and all integers and fractions within the range.

[0061] In these examples, unless otherwise specified, the parts and percentages are by mass.

[0062] "Parts by mass" refers to the basic measurement unit representing the mass ratio relationship of multiple components. 1 part can represent any unit mass, such as 1 g or 2.689 g, etc. Suppose we say that the mass parts of component A is a parts and the mass parts of component B is b parts, then it represents the mass ratio of component A to component B as a:b. Or, it represents the mass of component A as aK and the mass of component B as bK (K is any number representing a multiple factor). It should not be misunderstood that, different from the number of mass parts, the sum of the mass parts of all components is not limited to 100 parts.

[0063] "And / or" is used to indicate that either or both of the stated circumstances may occur. For example, A and / or B includes (A and B) and (A or B).

[0064] The present application provides a cathode precursor material for a sodium-ion battery based on the first aspect of the above problems. The vertical distance d from the arc fitted at the top of the primary particles of the cathode precursor material for the sodium-ion battery to the cross-section and the thickness s of the primary particles satisfy the relational expression:

[0065] 1 / 8 ≤ d / s ≤ 1 / 4.

[0066] It should be noted that, as Figure 1 or Figure 2 shown, in the front view of the loosely stacked primary particles, taking the upper vertex of the primary nanosheet at the edge of the primary particle as an endpoint, a cross-section line is made. The length of this cross-section line is equal to the thickness s of the primary particle (the thickness s refers to the average thickness of the primary particle). Taking the primary nanosheet at the top of the primary particle as a differential unit, the top of the primary particle with stacking faults can be approximately fitted into a smooth curve l. The distance from this smooth curve 1 to the cross-section line is d. When the vertical distance d (referring to the farthest vertical distance of the primary particle) and the thickness s satisfy the above relational expression, the curvature and radius of curvature of the smooth curve 1 are better. Even in the stacking arrangement mode of the primary nanosheets, the sodium ion absorption of the primary particle can be optimized;

[0067] When d / s is not within the range of 1 / 8 - 1 / 4, as Figure 3 shown, when the stacking fault degree of the dense primary particle is too low or too high; when it is too low, the sodium ion absorption is poor and the sintering activity is poor; when it is too high, the cathode particles after sintering are fine, and the capacity release and cycle performance deteriorate;

[0068] In some embodiments, the thickness s of the primary particle is 120 nm - 360 nm.

[0069] Optionally, the thickness s of the primary particle can be 120 nm, 180 nm, 240 nm, 300 nm, 360 nm, or any value between 120 nm - 360 nm.

[0070] In some embodiments, the thickness s of the primary particle and the gap width t between the primary particles satisfy the relational expression:

[0071] 1.0 ≤ s / t ≤ 7.5.

[0072] Optionally, s / t can be 1.5, 2, 3, 4, 5, 6, 7, or any value between 1.0 - 7.5.

[0073] When the gap width t is less than 45 nm, the gap between the primary particles is too small and too dense. When sintered into a polycrystalline cathode material, the volume of the primary particle increases, and there is a risk of expansion, extrusion, and cracking of the precursor sphere. When the gap width t is greater than 120 nm, the gap between the primary particles is too large, and there may be gaps on the surface of the polycrystalline cathode material formed by sintering, forming an electrolyte infiltration channel, resulting in a decrease in electrical performance.

[0074] When 1.0 ≤ s / t ≤ 7.5, the size of the primary particles reaches equilibrium with the width of the gaps between the primary particles, and the polycrystalline cathode material formed by sintering has high crystallinity, a dense and seamless surface, and good electrical properties.

[0075] In some embodiments, the width t of the gaps between the primary particles is 45 nm - 120 nm.

[0076] Optionally, the width t of the gaps between the primary particles can be 45 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, 110 nm, 120 nm, or any value between 45 nm - 120 nm.

[0077] In some embodiments, the sodium-ion battery cathode precursor material satisfies at least one of the following conditions:

[0078] A. The D50 of the sodium-ion battery cathode precursor material is 7 μm - 12 μm;

[0079] Optionally, the D50 of the sodium-ion battery cathode precursor material can be 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, or any value between 7 μm - 12 μm;

[0080] B. The tap density TD of the sodium-ion battery cathode precursor material is ≥ 1.4 g / cm 3 ;

[0081] Optionally, the tap density TD of the sodium-ion battery cathode precursor material can be 1.4 g / cm 3 , 1.5 g / cm 3 , 1.6 g / cm 3 , 1.7 g / cm 3 , 1.8 g / cm 3 , 1.9 g / cm 3 , 2.0 g / cm 3 or any value greater than or equal to 1.4 g / cm 3 ;

[0082] C. The specific surface area SSA of the sodium-ion battery cathode precursor material is 2 m 2 / g - 5 m 2 / g;

[0083] Optionally, the specific surface area SSA of the sodium-ion battery cathode precursor material can be 2 m 2 / g, 3 m 2 / g, 4 m 2 / g, 5 m 2 / g, or 2 m 2 / g - 5 m2 Any value between / g;

[0084] D. The pH value of the positive electrode precursor material of the sodium ion battery is 8 - 10;

[0085] Optionally, the pH value of the positive electrode precursor material of the sodium ion battery can be 8, 8.5, 9, 9.5, 10 or any value between 8 - 10;

[0086] E. Na in the positive electrode precursor material of the sodium ion battery + content ≤ 200 ppm, SO4 2- content ≤ 2000 ppm;

[0087] Optionally, the Na in the positive electrode precursor material of the sodium ion battery + content can be 100 ppm, 120 ppm, 140 ppm, 160 ppm, 180 ppm, 200 ppm or any value less than or equal to 200 ppm, and the SO4 2- content can be 1000 ppm, 1200 ppm, 1400 ppm, 1600 ppm, 1800 ppm, 2000 ppm or any value less than or equal to 2000 ppm;

[0088] F. The mass content of water in the positive electrode precursor material of the sodium ion battery ≤ 0.60%;

[0089] Optionally, the mass content of water in the positive electrode precursor material of the sodium ion battery can be 0.40%, 0.45%, 0.50%, 0.55%, 0.60% or any value less than or equal to 0.60%;

[0090] G. The positive electrode precursor material of the sodium ion battery is spherical and / or quasi-spherical;

[0091] H. The chemical formula of the positive electrode precursor material of the sodium ion battery is Ni a Fe b Mn c R (1-a-b-c) (OH)2; where 0.1 ≤ a ≤ 0.4, 0 < b ≤ 0.3, 0 < c ≤ 0.7, 0.9 ≤ a + b + c ≤ 1, and R is selected from one or more of the elements Zn, Mg, Ti, Cu, Ca, W, Al, Co, Zr;

[0092] Exemplarily, a can be 0.1, 0.2, 0.3, 0.4, or any value between 0.1 and 0.4; b can be 0.1, 0.2, 0.3, or any value between 0.1 and 0.3; c can be 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, or any value between 0.1 and 0.7; a + b + c can be 0.9, 0.95, 1, or any value between 0.9 and 1;

[0093] I. The sodium ion battery cathode precursor material includes an O3-type sodium ion battery cathode precursor material.

[0094] It should be noted that the O3-type cathode material can accommodate a higher content of sodium element, thereby releasing a higher discharge specific capacity, which requires the introduction of a large amount of sodium source in the sintering reaction. However, sodium element has a large ionic radius and cannot be efficiently inserted / extracted from the cathode. A large part of the sodium element will accumulate on the material surface and cannot be fully diffused into the lattice interior, resulting in a deviation between the sodium ion content in the material bulk phase and the theoretical value. And a high residual alkali content will lead to a lower capacity release and serious side reactions, deteriorating the battery performance.

[0095] The second aspect of the present application provides a preparation method of the sodium ion battery cathode precursor material, including:

[0096] In an inert atmosphere, a mixed metal salt solution, a doped metal salt solution, a complexing agent, and a precipitating agent are introduced into the bottom liquid in a flowing manner, and a first reaction is carried out under stirring, controlling the solution pH value in the first reaction process to continuously decrease, and then the mixed metal salt solution, the doped metal salt solution, the complexing agent, and the precipitating agent are introduced, and the pH is maintained constant for a second reaction to prepare the sodium ion battery cathode precursor material;

[0097] Among them, the mixed metal salt solution includes manganese salt, nickel salt, and iron salt.

[0098] In some embodiments, the preparation method of the sodium ion battery cathode precursor material satisfies at least one of the following conditions:

[0099] A. The manganese salt includes one or more of manganese sulfate, manganese chloride, manganese acetate, and manganese nitrate;

[0100] B. The nickel salt includes one or more of nickel sulfate, nickel chloride, nickel acetate, and nickel nitrate;

[0101] C. The iron salt includes one or more of ferrous sulfate, ferrous chloride, ferrous acetate, and ferrous nitrate;

[0102] D. The doped metal salt in the doped metal salt solution includes one or more of sulfates, chlorides, acetates, and nitrates containing doped elements;

[0103] E. The complexing agent includes one or more of ammonia water, oxalic acid, citric acid or sodium citrate;

[0104] F. The precipitating agent includes one or more of sodium hydroxide, potassium hydroxide, sodium carbonate, potassium carbonate;

[0105] G. The inert gas in the inert atmosphere includes nitrogen and / or argon;

[0106] H. The bottom liquid is a mixture of the water, the precipitating agent and the complexing agent;

[0107] I. The pH value of the bottom liquid is 12.00 - 13.00;

[0108] Optionally, the pH value of the bottom liquid can be 12.0, 12.1, 12.2, 12.3, 12.4, 12.5, 12.6, 12.7, 12.8, 12.9, 13 or any value between 12.00 - 13.00;

[0109] J. The end - point pH of the first reaction is 11.40 - 11.60, and the time is 0.5 h - 1 h;

[0110] Optionally, the end - point pH of the first reaction can be 11.40, 11.45, 11.5, 11.55, 11.6 or any value between 11.40 - 11.60, and the time can be 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1 h or any value between 0.5 h - 1 h;

[0111] It should be noted that when the pH of the first reaction continuously decreases until it reaches 11.40 - 11.60, at this time, the supersaturation in the reaction kettle reaches a low value, the homogeneous nucleation driving force is low, and the precursor begins to grow.

[0112] K. The temperatures of the first reaction and the second reaction are both 55 °C - 65 °C;

[0113] Optionally, the temperatures of the first reaction and the second reaction can be 55 °C, 56 °C, 57 °C, 58 °C, 59 °C, 60 °C, 61 °C, 62 °C, 63 °C, 64 °C, 65 °C or any value between 55 °C - 65 °C;

[0114] It should be noted that when the reaction temperature is in the range of 55 °C - 65 °C, at a higher temperature, the primary nanosheets tend to stack along the (001) direction, and the packing density of the precursor primary particles increases.

[0115] L. The pH of the second reaction is 11.40 - 11.60.

[0116] Optionally, the pH of the second reaction can be 11.40, 11.45, 11.5, 11.55, 11.6 or any value between 11.40 and 11.60.

[0117] It should be noted that when the pH of the second reaction is maintained within the range of 11.40 - 11.60, stacking faults occur in the growth of the primary nanosheets at higher pH values.

[0118] The third aspect of the present application provides a cathode material, which is obtained by mixing and sintering the sodium-ion battery cathode precursor material described above with a sodium source.

[0119] The fourth aspect of the present application provides a sodium-ion battery, including the cathode material described above.

[0120] The fifth aspect of the present application provides an electrical device, including the sodium-ion battery described above.

[0121] It should be noted that the electrical device can be, but is not limited to, mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc.; among them, mobile devices can include, but are not limited to, at least one of mobile phones, laptop computers, etc.; electric vehicles can include, but are not limited to, at least one of pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.

[0122] The following will describe the implementation schemes of the present application in detail with specific examples. However, those skilled in the art will understand that the following examples are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. For those not specified in the examples, they are carried out under conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified in the manufacturer are all conventional products that can be obtained through commercial purchase.

[0123] In the examples, the reaction equipment for precipitating the O3-type sodium-ion battery cathode precursor material is a 1000L closed metal reaction kettle with three-layer blades. The blades are all four-inclined blade agitators, and the inclination angle of the agitator blades is 45°. The spread of the upper and lower four-inclined blades is 0.33 times the diameter of the kettle, and the spread of the middle inclined blade is 0.45 times the diameter of the kettle. The positions of the upper, middle, and lower agitators are 1 / 4, 2 / 4, and 3 / 4 from the top of the reaction kettle respectively. The reaction kettle is equipped with multiple feed pipes. The feed pipe orifices of the mixed salt solution and the doped salt solution are located at the center of the interval between the middle and lower agitators. Under the high-shear action of the middle agitator with a wide blade spread, sufficient and uniform mixing of the feed is achieved.

[0124] Example 1

[0125] This example provides an O3-type sodium-ion battery cathode precursor material and its preparation method. The chemical formula of the precursor material is Ni0.22 Fe 0.30 Mn 0.45 Zn 0.03 (OH)2, and the specific preparation method is as follows:

[0126] 1. Prepare a mixed salt solution:

[0127] Disperse nickel sulfate hexahydrate, ferrous sulfate heptahydrate, and manganese sulfate monohydrate in pure water, and continuously stir for 4 h under the condition that the stirring speed is 40 r / min to prepare a nickel-iron-manganese mixed salt solution; wherein, the total metal ion concentration is 2 mol / L, and in terms of mass ratio, Ni:Fe:Mn = 22:30:45. Filter and demagnetize the prepared mixed salt solution, and temporarily store it in a transfer tank;

[0128] 2. Prepare a doped salt solution:

[0129] Disperse zinc sulfate heptahydrate in pure water, add 30% ammonia water solution to the zinc salt solution, and the volume ratio of the zinc salt solution to the ammonia water solution is 40:1. Continuously stir for 4 h under the condition that the stirring speed is 40 r / min to prepare a doped salt solution, wherein the total metal ion concentration is 1 mol / L; filter and demagnetize the prepared doped zinc salt solution, and temporarily store it in a transfer tank;

[0130] 3. Prepare a reaction bottom liquid:

[0131] Add pure water to a 1000 L closed metal reaction kettle until it is almost full and introduce N2 for protection, with a nitrogen flow rate of 10 L / min. Add 500 mL of hydrazine hydrate to the reaction kettle, set the stirring speed to 200 r / min and continuously stir for 1 h; add 10 M sodium hydroxide solution and 30% ammonia water solution to the reaction kettle, adjust the ammonia concentration to 6 g / L, and adjust the pH value to between 12.20 - 12.30 of the off-line value;

[0132] 4. Start the reaction:

[0133] Set the stirring speed of the reaction equipment (reaction kettle) to 300 r / min, and heat the reaction kettle to 60 °C by circulating water heating. Introduce the mixed salt solution, doped zinc salt solution, complexing agent, and precipitating agent obtained in Step 1 and Step 2 into the reaction kettle in parallel, wherein the flow rate of the mixed salt solution is 60 L / h, and the flow rate of the doped zinc salt solution is 1.86 L / h. Under the condition of inert gas protection, control the pH value in the reaction kettle to continuously decrease within 30 min, and measure it with a Leici PHSJ-4F pH meter at 50 °C. Stop when the pH in the kettle is adjusted to 11.60 and stops decreasing. Continue to introduce the mixed salt solution, doped zinc salt solution, precipitating agent, and complexing agent, and keep the pH within the range of 11.60 ± 3. Stop when D50 = 8 μm;

[0134] 5. Post-treatment:

[0135] Centrifuge the reaction slurry in Step 4 with a centrifuge and filter off the mother liquor. First, wash it with 0.1 mol / L sodium hydroxide solution for 2 h, then wash it with hot pure water for 10 h and take it out, dry it in an oven at 120 °C for 12 h, and then pass it through a 325-mesh sieve to obtain the O3-type sodium-ion battery cathode precursor material.

[0136] The morphology of the O3-type sodium-ion battery cathode precursor material is as Figure 4 shown, where Figure 4 Taking the upper vertex of the primary nanosheet at the edge of the primary particle as the end point, a transverse line is made. The length of this transverse line is equal to the thickness s of the primary particle, and the distance from the fitted arc to the cross-section is the vertical distance d. The data of the vertical distance d and the thickness s are shown in Table 1.

[0137] The schematic diagram of the crack width t and the thickness s of the O3-type sodium-ion battery cathode precursor material is as Figure 5 shown;

[0138] Figure 6 is the SEM image of the O3-type sodium-ion battery cathode precursor material;

[0139] The physical properties of the O3-type sodium-ion battery cathode precursor material are shown in Table 2.

[0140] This example also provides a cathode material. Weigh and mix the O3-type sodium-ion battery cathode precursor material obtained in Step 5 above and sodium carbonate in a molar ratio of 1:0.98, and then put it into a box furnace for sintering. Heat it up to 900 °C at a rate of 5 °C / min, keep it at this temperature for 16 h, and then cool it naturally to room temperature to obtain the cathode material.

[0141] Example 2

[0142] The difference in process parameters from Example 1 is that during the start-up reaction process of the O3-type sodium-ion battery cathode precursor material in Step 4, after the pH in the autoclave is adjusted to 11.40 and stops dropping, then the mixed salt solution, doped salt solution, precipitant, and complexing agent are introduced.

[0143] Example 3

[0144] The difference in process parameters from Example 1 is that during the start-up reaction process of the O3-type sodium-ion battery cathode precursor material in Step 4, after the pH in the autoclave is adjusted to 11.50 and stops dropping, then the mixed salt solution, doped salt solution, precipitant, and complexing agent are introduced, and the reaction autoclave is heated up to 65 °C by means of circulating water heating.

[0145] Example 4

[0146] The difference in process parameters from Example 1 is that during the start of the reaction in Step 4 for the O3-type sodium-ion battery cathode precursor material, the reaction kettle is heated to 65 °C by circulating water heating.

[0147] Example 5

[0148] The difference in process parameters from Example 1 is that during the start of the reaction in Step 4 for the O3-type sodium-ion battery cathode precursor material, after the pH in the kettle is adjusted to 11.40 and stops decreasing, a mixed salt solution, a doping salt solution, a precipitant, and a complexing agent are introduced, and the reaction kettle is heated to 55 °C by circulating water heating.

[0149] Comparative Example 1

[0150] The difference in process parameters from Example 1 is that during the start of the reaction in Step 4 for the precursor material, the pH value is not adjusted, and a mixed salt solution, a doping salt solution, a precipitant, and a complexing agent are directly introduced until a precursor material with a target particle size is obtained.

[0151] Comparative Example 2

[0152] The difference in process parameters from Example 1 is that during the start of the reaction in Step 4 for the precursor material, the pH value is adjusted to 11.8, and then a mixed salt solution, a doping salt solution, a precipitant, and a complexing agent are introduced until a precursor material with a target particle size is obtained.

[0153] Comparative Example 3

[0154] The difference in process parameters from Example 1 is that during the start of the reaction in Step 4 for the precursor material, the pH value is adjusted to 11.2, and then a mixed salt solution, a doping salt solution, a precipitant, and a complexing agent are introduced until a precursor material with a target particle size is obtained.

[0155] Comparative Example 4

[0156] The difference in process parameters from Example 1 is that during the start of the reaction in Step 4 for the precursor material, the reaction kettle is heated to 70 °C by circulating water heating.

[0157] Comparative Example 5

[0158] The difference in process parameters from Example 1 is that during the start of the reaction in Step 4 for the precursor material, the reaction kettle is heated to 50 °C by circulating water heating.

[0159] Comparative Example 6

[0160] The difference in process parameters from Example 1 is that the pH value of the bottom liquid is 13.2.

[0161] The data of the vertical distance d and thickness s of the precursors provided in the above examples and comparative examples are shown in Table 1.

[0162] Table 1 Data of vertical distance d, thickness s, and slit width t

[0163]

[0164] The physical property data of the precursors provided by the above-mentioned examples and comparative examples are shown in Table 2.

[0165] Table 2 Physical property data

[0166]

[0167] The precursors provided by the above-mentioned examples and comparative examples were subjected to ICP testing, and the results are shown in detail in Table 3.

[0168] Table 3 ICP testing

[0169]

[0170] Electrochemical performance testing:

[0171] The layered oxide cathode material was prepared into a cathode electrode sheet and the battery was subjected to electrochemical performance testing. The mass percentages of the cathode material, binder, and conductive agent in the cathode slurry were 80:1:1. The conductive agent used was sp, the binder was PVDF, the current collector used was aluminum foil, the battery case model was CR2032, and the electrolyte was NaPF6-diglyme (DIGLYME) electrolyte. Charge-discharge cycling tests were carried out at 2.0 - 4.0V. The test results are shown in Table 4. The discharge capacity at 0.2C was 147 mAh / g, the reversible specific capacity at 1C rate was 139 mAh / g, and the cycle retention rate after 300 cycles was 95%. The specific results are shown in Table 4.

[0172] Table 4 Electrochemical performance testing

[0173]

[0174] Analysis:

[0175] From the comparison of all examples and all comparative examples, it can be seen that when 0.125 ≤ d / s ≤ 0.25, the electrical properties such as discharge capacity and cycle retention rate are better released.

[0176] Compared with Example 4 and Example 5, the discharge capacity and cycle retention rate of Examples 1, 2, and 3 are better, indicating that on the basis of satisfying 0.125 ≤ d / s ≤ 0.25, controlling the thickness s between 120 nm and 360 nm can further improve the discharge capacity and cycle retention rate.

[0177] It can be seen from Table 1 and Table 4 that the discharge capacity and cycle retention rate are more excellent when 0.125 ≤ d / s ≤ 0.25 and 1.0 ≤ s / t ≤ 7.5 are satisfied simultaneously. Further, on the basis of satisfying 0.125 ≤ d / s ≤ 0.25 and 1.0 ≤ s / t ≤ 7.5, when the slit width t is 45 nm - 120 nm, the electrical properties such as discharge capacity and cycle retention rate are released better.

[0178] From the test results of the above-mentioned examples and comparative examples, it can be seen that Examples 1 - 3 satisfy 0.125 ≤ d / s ≤ 0.25, 1.0 ≤ s / t ≤ 7.5, the thickness s is 120 nm - 360 nm, and the slit width t is 45 nm - 120 nm, and their electrical properties such as discharge capacity and cycle retention rate are released better; in Example 4, because the primary particle thickness s is higher than 360 nm, and s / t = 7.33 belongs to the upper edge of the range of [1.0, 7.5], the positive electrode grain size is larger, there is a risk of expansion and extrusion, and the crystallinity is poor; in Example 5, because the primary particle thickness s is lower than 120 nm and the slit width t = 113 nm, which belongs to the upper edge of the 45 nm - 120 nm interval, the positive electrode grain size is relatively small; therefore, compared with Examples 1 - 3, the electrical properties such as discharge capacity and cycle retention rate of the two are slightly worse. In Comparative Examples 1, 2, and 6, because the pH value is set higher than 11.60, the particle size D50 is smaller, and the thickness s and d / s values do not meet the requirements, and the electrochemical performance is poor; in Comparative Example 3, because the pH is set lower than 11.40, the s value is small, and d / s is greater than 0.25, and the electrochemical performance is poor; in Comparative Examples 4 and 5, because the reaction temperature is not within the range of 55 - 65 °C, the thickness s and d / s values do not meet the requirements, and the electrochemical performance is poor.

[0179] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and are not intended to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

[0180] In addition, those skilled in the art can understand that although some embodiments herein include certain features included in other embodiments rather than other features, the combination of the features of different embodiments means that it is within the scope of the present application and forms different embodiments. For example, in the above claims, any one of the claimed embodiments can be used in any combination. The information disclosed in this background art section is only intended to deepen the understanding of the overall background art of the present application, and should not be regarded as an admission or any form of implication that this information constitutes prior art already known to those skilled in the art.

Claims

1. A method for preparing a sodium ion battery positive electrode precursor material, characterized in that: include: In an inert atmosphere, a mixed metal salt solution, a doped metal salt solution, a complexing agent, and a precipitant are simultaneously introduced into a base liquid, a first reaction is performed under stirring, a pH value of the solution during the first reaction is controlled to continuously decrease, and then the mixed metal salt solution, the doped metal salt solution, the complexing agent, and the precipitant are introduced, and a second reaction is performed while maintaining a constant pH value to prepare the sodium ion battery positive electrode precursor material; Wherein, the mixed metal salt solution includes manganese salt, nickel salt and iron salt; The pH value of the base solution is 12.00-13.00; The endpoint pH of the first reaction is 11.40-11.60; The pH of the second reaction is 11.40-11.60; The temperature of the first reaction and the second reaction is 55°C-65°C; The vertical distance d from the arc fitted at the top of the primary particle of the sodium ion battery positive electrode precursor material to the cross section and the thickness s of the primary particle satisfy the relationship: 1 / 8≤d / s≤1 / 4; The thickness s of the primary particles is 120nm-360nm; The thickness s of the primary particles and the gap width t between the primary particles satisfy the relationship: 1.0≤s / t≤7.5; The gap width t between the primary particles is 45nm-120nm; The doping metal in the doping metal salt solution includes one or more of Zn, Mg, Ti, Cu, Ca, W, Al, Co, and Zr.

2. The method for preparing a positive electrode precursor material for a sodium ion battery according to claim 1, characterized in that: At least one of the following conditions is met: A. The D50 of the sodium ion battery positive electrode precursor material is 7 μm-12 μm; B. The tap density TD of the sodium ion battery positive electrode precursor material is ≥ 1.4 g / cm 3 ; C. The specific surface area SSA of the sodium ion battery positive electrode precursor material is 2m 2 / g-5m 2 / g; D. The pH value of the sodium ion battery positive electrode precursor material is 8-10; E. Na in the sodium ion battery positive electrode precursor material + Content ≤200ppm, SO4 2- Content ≤2000ppm; F. The mass content of water in the sodium ion battery positive electrode precursor material is ≤0.60%; G. The sodium ion battery cathode precursor material is spherical and / or spherical; H. The chemical formula of the sodium ion battery positive electrode precursor material is Ni a Fe b Mn c R (1-a-b-c) (OH)2; wherein 0.1≤a≤0.4, 0<b≤0.3, 0<c≤0.7, 0.9≤a+b+c≤1, and R is selected from one or more of Zn, Mg, Ti, Cu, Ca, W, Al, Co, and Zr; I. The sodium ion battery positive electrode precursor material includes an O3 type sodium ion battery positive electrode precursor material.

3. The method for preparing a positive electrode precursor material for a sodium ion battery according to claim 1 or 2, characterized in that: At least one of the following conditions is met: A. the manganese salt comprises one or more of manganese sulfate, manganese chloride, manganese acetate and manganese nitrate; B. the nickel salt comprises one or more of nickel sulfate, nickel chloride, nickel acetate and nickel nitrate; C. the iron salt comprises one or more of ferrous sulfate, ferrous chloride, ferrous acetate and ferrous nitrate; D. the doped metal salt in the doped metal salt solution includes one or more of sulfate, chloride, acetate and nitrate containing the doping element; E. the complexing agent includes one or more of ammonia water, oxalic acid, citric acid or sodium citrate; F. the precipitating agent comprises one or more of sodium hydroxide, potassium hydroxide, sodium carbonate and potassium carbonate; G. the inert gas in the inert atmosphere comprises nitrogen and / or argon; H. the base liquid is a mixture of the water, the precipitant and the complexing agent; J. The time of the first reaction is 0.5h-1h.

4. A positive electrode material, characterized in that The sodium ion battery positive electrode precursor material prepared by the method for preparing the sodium ion battery positive electrode precursor material according to any one of claims 1 to 3 is mixed with a sodium source and sintered.

5. A sodium ion battery, characterized in that: Comprising the positive electrode material as claimed in claim 4.

6. An electrical equipment, characterized in that: Including the sodium ion battery as described in claim 5.

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