Polycrystalline structure oxide precursor as well as preparation method and application thereof

Abstract

The invention relates to a polycrystalline structure oxide precursor and a preparation method and application thereof. The preparation method comprises the following steps: preparing a mixed metal salt solution; the mixed metal salt solution and a binding agent are heated and mixed, a first solution is obtained, the binding agent is selected from a synthetic organic matter material and / or a natural high polymer material, and the use amount of the binding agent is 2%-12% of the mass of the first solution; carrying out pre-concentration and spray pyrolysis on the first solution to obtain a polycrystalline structure oxide precursor; according to the preparation method, the polycrystalline structure oxide precursor can be synthesized in one step, and the precursor has excellent dispersity and uniformity and can be used for preparing a battery positive electrode material, so that the specific discharge capacity, the rate capability and the stability can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and particularly to a polycrystalline structure oxide precursor, a preparation method thereof, and an application thereof. Background Art

[0002] In the field of batteries, traditional methods for preparing oxide precursors mainly include co-precipitation method, spray pyrolysis method, etc. Among them, impurity ions such as sodium, sulfur, calcium, etc. will be introduced during the co-precipitation process, and a large amount of auxiliary materials are required, resulting in a large amount of pollutants generated during the preparation process and relatively high environmental protection costs.

[0003] Although spray pyrolysis can avoid the introduction of impurity ions and reduce costs, traditional spray pyrolysis methods are only applicable to the preparation of single crystal structures. Due to the low activity of single crystal structure oxide precursors, more energy consumption is required for sintering into a positive electrode, and the particles of single crystal structure oxide precursors are relatively large, making cation diffusion more difficult, which is not conducive to improving the discharge specific capacity. In addition, traditional spray pyrolysis usually requires secondary calcination to obtain a stable oxide precursor, but the precursor obtained by secondary calcination has serious irregular agglomeration and poor sphericity, resulting in more energy consumption and lower discharge specific capacity required for sintering the positive electrode. Summary of the Invention

[0004] Based on this, in view of the above problems, it is necessary to provide a polycrystalline structure oxide precursor, a preparation method thereof, and an application thereof; the preparation method can synthesize a polycrystalline structure oxide precursor in one step, and this precursor has excellent dispersibility and uniformity. When used for preparing a battery positive electrode material, it can improve the discharge specific capacity, rate performance, and stability, and reduce costs.

[0005] A preparation method of a polycrystalline structure oxide precursor, the preparation method comprising the following steps:

[0006] Prepare a mixed metal salt solution;

[0007] Heat and mix the mixed metal salt solution with a binder to obtain a first solution, wherein the binder is selected from synthetic organic materials and / or natural polymer materials, and the dosage of the binder is 2%-12% of the mass of the first solution;

[0008] The first solution is pre-concentrated and spray pyrolyzed to obtain a polycrystalline structure oxide precursor.

[0009] In one embodiment, the synthetic organic material satisfies at least one of the following conditions:

[0010] (1) The molecular size of the synthetic organic material is 1 nm - 60 nm;

[0011] (2) The degree of polymerization of the synthetic organic material is 200 - 2000.

[0012] In one embodiment, when the concentration of the mixed metal salt solution is increased by 10 g / L, the proportion of the binder in the first solution increases by 0.1%-2.5%.

[0013] In one embodiment, the binder satisfies at least one of the following conditions:

[0014] (1) The binder is selected from the mixture of synthetic organic materials and natural polymer materials;

[0015] (2) The dosage of the binder is 3%-8% of the mass of the first solution;

[0016] (3) The synthetic organic material is selected from at least one of polyethylene glycol, polyvinyl alcohol, polyvinyl butyral, sodium polyacrylate or polyurethane;

[0017] (4) The natural polymer material is selected from at least one of lignin, cellulose, starch or chitosan.

[0018] In one embodiment, the mixed metal salt solution is prepared according to the stoichiometric ratio of Cu a M 1-a O2, where M is selected from at least one of Ni, Fe or Mn, and 0.1 ≤ a ≤ 0.9.

[0019] In one embodiment, the mixed metal salt solution satisfies at least one of the following conditions:

[0020] (1) The total concentration of metal ions in the mixed metal salt solution is 80 g / L - 280 g / L;

[0021] (2) In the mixed metal salt solution, the copper salt is selected from at least one of cuprous chloride, copper chloride, cuprous sulfate, copper sulfate, cuprous nitrate or copper nitrate;

[0022] (3) When M is selected from Ni, in the mixed metal salt solution, the nickel salt is selected from at least one of nickel chloride, nickel sulfate or nickel nitrate;

[0023] (4) When M is selected from Fe, in the mixed metal salt solution, the iron salt is selected from at least one of ferrous chloride, ferric chloride, ferrous sulfate, ferric sulfate, ferrous nitrate or ferric nitrate;

[0024] (5) When M is selected from Mn, in the mixed metal salt solution, the manganese salt is selected from at least one of manganese chloride, manganese sulfate or manganese nitrate.

[0025] In one of the embodiments, in the step of heating and mixing the mixed metal salt solution with the binder, the temperature is 40°C - 90°C, the stirring speed is 100 r / min - 300 r / min, and the time is 0.5 h - 3 h.

[0026] In one of the embodiments, the steps of pre-concentrating and spray pyrolyzing the first solution satisfy at least one of the following conditions:

[0027] (1) The total concentration of metal ions after pre-concentration of the first solution is 200 g / L - 400 g / L;

[0028] (2) During the spray pyrolysis process, the inlet flow rate of the first solution is 0.2 m 3 / h - 1.0 m 3 / h;

[0029] (3) The temperature of the spray pyrolysis is 600°C - 900°C.

[0030] A polycrystalline structure oxide precursor obtained by the preparation method of the polycrystalline structure oxide precursor as described above, wherein the polycrystalline structure oxide precursor is secondary particles formed by the aggregation of primary particles.

[0031] In one of the embodiments, the polycrystalline structure oxide precursor satisfies at least one of the following conditions:

[0032] (1) The D 50 of the primary particles is 0.1 μm to 1 μm;

[0033] (2) The D 50 of the secondary particles is 5 μm to 20 μm;

[0034] (3) The D max of the secondary particles is 30 μm to 50 μm;

[0035] (4) The K 90 of the secondary particles is less than 3;

[0036] (5) The specific surface area of the polycrystalline structure oxide precursor is 7 m 2 / g - 20 m 2 / g;

[0037] (6) The tapped density of the polycrystalline structure oxide precursor is 1.1 g / cm 3 - 2.5 g / cm 3 .

[0038] A cathode material prepared from the polycrystalline structure oxide precursor as described above.

[0039] A positive electrode sheet includes a positive electrode current collector and a positive electrode material layer provided on the surface of the positive electrode current collector, and the positive electrode material layer includes the positive electrode material as described above.

[0040] A secondary battery includes the positive electrode sheet as described above.

[0041] In the preparation method of the present invention, by heating and mixing the prepared mixed metal salt solution with a binder of a specific type and dosage, the binder can quickly and uniformly penetrate between the ions of the mixed metal salt solution, which is beneficial to the combination of the binder and metal ions to form stable chemical bonds, enabling the binder to fully react with metal ions for curing and / or cross-linking reactions, thereby fixing the metal ions together to achieve a good bonding effect. In addition, the specific mixed metal salt solution and the binder of a specific type and dosage have good stability, compatibility, and applicability, which are more conducive to ensuring effective fixation between metal ions.

[0042] Furthermore, during the process of pre-concentration and spray pyrolysis of the first solution, the bonded metal ions quickly crystallize and nucleate to form a relatively dense and uniform polycrystalline structure. At the same time, the binder distributed between the metal ions decomposes into pollution-free gases such as carbon dioxide and nitrogen and overflows at high temperature, thus not affecting the performance of the subsequent oxide precursor product, and also being conducive to improving the dispersion effect of the oxide precursor and avoiding irregular agglomeration.

[0043] Therefore, the preparation method of the present invention can synthesize a polycrystalline structure oxide precursor in one step. This precursor has excellent dispersibility and uniformity. When used to prepare a battery positive electrode material, it can improve the discharge specific capacity, rate performance, and stability, and reduce costs. Description of the Drawings

[0044] Figure 1 is a process flow chart of the preparation method of the present invention;

[0045] Figure 2 is a scanning electron microscope image (SEM) of the polycrystalline structure oxide precursor prepared in Example 1 and the effect diagram after argon ion polishing (CP) sample preparation. Among them, a is the SEM image, and b is the CP-SEM image;

[0046] Figure 3 is the SEM image of the oxide precursor prepared in Comparative Example 1;

[0047] Figure 4 is the SEM image and CP-SEM image of the polycrystalline structure oxide precursor prepared in Comparative Example 2. Among them, a is the SEM image, and b is the CP-SEM image;

[0048] Figure 5SEM and CP-SEM images of the polycrystalline structure oxide precursor prepared in Comparative Example 3, where a is the SEM image and b is the CP-SEM image;

[0049] Figure 6 SEM image of the oxide precursor prepared in Comparative Example 4;

[0050] Figure 7 Cycling performance comparison chart, where a is the cycling performance curve of the cathode material prepared in Example 1 and b is the cycling performance curve of the cathode material prepared in Comparative Example 1;

[0051] Figure 8 Charge-discharge capacity comparison chart, where a is the charge-discharge capacity curve of the cathode material prepared in Example 1 and b is the charge-discharge capacity curve of the cathode material prepared in Comparative Example 1;

[0052] Figure 9 Rate performance comparison chart, where a is the rate performance of the cathode material prepared in Example 1 and b is the rate performance of the cathode material prepared in Comparative Example 1. Detailed Description of the Invention

[0053] For the convenience of understanding the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure content of the present invention more thorough and comprehensive.

[0054] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments or examples and are not intended to limit the present invention.

[0055] Combined with Figure 1 As shown, a method for preparing a polycrystalline structure oxide precursor provided by the present invention, the preparation method comprising the following steps:

[0056] S1, preparing a mixed metal salt solution;

[0057] S2, heating and mixing the mixed metal salt solution with a binder to obtain a first solution, wherein the binder is selected from synthetic organic materials and / or natural polymer materials, and the amount of the binder is 2%-12% of the mass of the first solution;

[0058] S3, subjecting the first solution to pre-concentration and spray pyrolysis to obtain a polycrystalline structure oxide precursor.

[0059] In step S1, preferably, the mixed metal salt solution is in accordance with Cua M 1-a Prepare with a stoichiometric ratio of O2, where M is selected from at least one of Ni, Fe, or Mn, 0.1 ≤ a ≤ 0.9. Using Cu as the main element and at least one of Ni, Fe, and Mn to cooperate in preparing the secondary battery oxide precursor can not only further control the cost of the secondary battery, making the oxide precursor more advantageous in terms of raw material cost, but also help improve the capacity, rate performance, and stability of the positive electrode.

[0060] Among them, Ni can play a role in stabilizing the structure and improving the specific capacity of the material; Fe can inhibit phase transformation and improve the conductivity of the material; Cu can improve the rate performance, inhibit the Jahn-Teller effect, improve the cycle stability, and improve the air stability; Mn can improve the structural stability of the material. Combining different elements in different molar ratios can effectively improve the capacity, rate performance, and stability of the positive electrode.

[0061] Preferably, the mixed metal salt solution is selected from a metal salt solution containing Cu, Fe, and Mn or a metal salt solution containing at least Ni and Cu. Among them, the metal salt solution containing at least Ni and Cu is selected from a metal salt solution containing Ni, Cu, Fe, and Mn, a metal salt solution containing Ni, Cu, and Fe, or a metal salt solution containing Ni and Cu.

[0062] More preferably, when the mixed metal salt solution is selected from a metal salt solution containing Cu, Fe, and Mn, the molar ratio of Cu, Fe, and Mn in the mixed metal salt solution is preferably (0.1 - 0.9):(0.05 - 0.5):(0.05 - 0.85); when the mixed metal salt solution is selected from a metal salt solution of Ni, Cu, Fe, and Mn, the molar ratio of Ni, Cu, Fe, and Mn in the mixed metal salt solution is preferably (0.2 - 0.6):(0.05 - 0.4):(0.3 - 0.6):(0.2 - 0.45); when the mixed metal salt solution is selected from a metal salt solution containing Ni, Cu, and Fe, the molar ratio of Ni, Cu, and Fe in the mixed metal salt solution is preferably (0.3 - 0.6):(0.2 - 0.6):(0.1 - 0.5); when the mixed metal salt solution is selected from a metal salt solution containing Ni and Cu, the molar ratio of Ni and Cu in the mixed metal salt solution is preferably (0.3 - 0.7):(0.3 - 0.7).

[0063] Preferably, the total concentration of metal ions in the mixed metal salt solution is 80 g / L - 280 g / L, more preferably 100 g / L - 200 g / L. By further adjusting the concentration of metal ions in the mixed metal salt solution, it is beneficial to reduce the interaction between metal ions and avoid the formation of a relatively dense hydrated structure between metal ions, thereby facilitating the penetration of the binder and enabling the binder to more fully undergo curing and / or cross-linking reactions with metal ions, achieving a good bonding effect.

[0064] Optionally, in the mixed metal salt solution, the copper salt includes but is not limited to at least one of cuprous chloride, copper chloride, cuprous sulfate, copper sulfate, cuprous nitrate or copper nitrate.

[0065] When M is selected from Ni, in the mixed metal salt solution, the nickel salt includes but is not limited to at least one of nickel chloride, nickel sulfate or nickel nitrate.

[0066] When M is selected from Fe, in the mixed metal salt solution, the iron salt includes but is not limited to at least one of ferrous chloride, ferric chloride, ferrous sulfate, ferric sulfate, ferrous nitrate or ferric nitrate.

[0067] When M is selected from Mn, in the mixed metal salt solution, the manganese salt includes but is not limited to at least one of manganese chloride, manganese sulfate or manganese nitrate.

[0068] It should be noted that the mixed metal salt solution can be prepared by first preparing single metal salt solutions and then mixing multiple single metal salt solutions in proportion, or directly mixing single metal salts in proportion to form the mixed metal salt solution. The present invention does not limit this.

[0069] When preparing the single metal salt solution, the concentration of the single metal ion in the single metal salt solution is 80 g / L - 280 g / L, preferably 100 g / L - 200 g / L.

[0070] In step S2, by heating and mixing the prepared mixed metal salt solution with a binder of a specific type and dosage, the binder can quickly and uniformly penetrate between the ions of the mixed metal salt solution, which is beneficial for the binder to combine with metal ions to form stable chemical bonds, enabling the binder to fully undergo curing and / or cross-linking reactions with metal ions, thereby fixing the metal ions together to achieve a good bonding effect. In addition, the specific mixed metal salt solution and the binder of a specific type and dosage have good stability, compatibility and applicability, which is more conducive to ensuring an effective fixing effect between metal ions.

[0071] Preferably, for every 10 g / L increase in the concentration of the mixed metal salt solution, the proportion of the binder in the first solution increases by 0.1%-2.5%, more preferably 0.4%-1.5%. By synergistically regulating the amounts of the binder and the mixed metal salt solution, it is beneficial to further improve the bonding effect, and thus improve the uniformity, tap density, specific surface area and dispersion effect of the polycrystalline structure oxide precursor.

[0072] Preferably, the amount of the binder is 3%-8% of the mass of the first solution, which is beneficial to further improve the size morphology, tap density and specific surface area of the polycrystalline structure oxide precursor.

[0073] Preferably, the molecular size of the synthetic organic material is 1 nm - 60 nm, more preferably 5 nm - 40 nm, and the degree of polymerization of the synthetic organic material is preferably 200 - 2000. By regulating the molecular size and degree of polymerization of the synthetic organic material, it is beneficial to further improve the penetration effect of the binder and achieve stronger mechanical adhesion.

[0074] Preferably, the binder is selected from the mixture of synthetic organic materials and natural polymer materials. Due to the relatively large molecular size of natural polymer materials, the long-chain structure of natural polymer materials can entangle with metal ions to form stable complexes, which is beneficial to increase the wettability and adhesion force on the surface of the complexes. At the same time, the synthetic organic material further binds the complexes and metal ions by virtue of its excellent mechanical adhesion, ion exchange effect and intermolecular force, so that the bonding effect is better.

[0075] Optionally, the synthetic organic material includes but is not limited to at least one of polyethylene glycol, polyvinyl alcohol, polyvinyl butyral, sodium polyacrylate or polyurethane, which has the characteristics of high permeability and stability and can form coordination bonds or hydrogen bonds with metal ions, being beneficial to achieving good bonding effects.

[0076] Optionally, the natural polymer material includes but is not limited to at least one of lignin, cellulose, starch or chitosan, which has good water solubility and biocompatibility and can form ionic bonds and hydrogen bonds in metal solutions, also being beneficial to achieving good bonding effects.

[0077] In step S3, during the pre-concentration and spray pyrolysis of the first solution, the bonded metal ions rapidly crystallize and nucleate to form a relatively dense and uniform-shaped polycrystalline structure. At the same time, the binder distributed among the metal ions decomposes into pollution-free gases such as carbon dioxide and nitrogen at high temperatures and overflows, thus not affecting the performance of the subsequent oxide precursor product, and also being beneficial to improving the dispersion effect of the oxide precursor and avoiding the generation of irregular agglomeration.

[0078] It should be noted that the polycrystalline structure is composed of multiple primary particles in an aggregated form, tightly packed to form a spherical or quasi-spherical structure with good sphericity. Although there may be a small amount of gaps between the primary particles, after cutting the spherical structure from the center, the cross-section of the spherical structure has no obvious core-shell structure, and there is no large-area void in the internal center, then this structure is defined as a solid structure.

[0079] In one embodiment, in the step of heating and mixing the mixed metal salt solution with the binder, the temperature is preferably 40°C - 90°C, the stirring speed is preferably 120 r / min - 180 r / min, and the time is preferably 1 h - 2 h.

[0080] In one embodiment, the steps of pre-concentrating and spray pyrolyzing the first solution satisfy at least one of the following conditions:

[0081] (1) The total concentration of metal ions in the first solution after pre-concentration is 200 g / L - 400 g / L, preferably 220 g / L - 320 g / L;

[0082] (2) During the spray pyrolysis process, the feed flow rate of the first solution is 0.2 m 3 / h - 1.0 m 3 / h;

[0083] (3) The temperature of the spray pyrolysis is 600°C - 900°C. It should be noted that the temperature of the spray pyrolysis is the working temperature of the pyrolysis device.

[0084] For the traditional spray method to prepare the precursor, it usually adopts a combination of low-temperature spray and high-temperature calcination treatment. Since the low-temperature spray pyrolysis is incomplete, it is necessary to cooperate with a long-time high-temperature post-treatment to achieve the pyrolysis effect. However, in the present invention, through one-step high-temperature spray pyrolysis, the pyrolysis reaction is directly completed within dozens of seconds to several minutes, without secondary calcination, greatly shortening the reaction time and reducing the energy consumption.

[0085] The present invention also provides a polycrystalline structure oxide precursor prepared by the above-mentioned preparation method. The polycrystalline structure oxide precursor is a secondary particle composed of aggregated primary particles.

[0086] Specifically, the shapes of both the primary particles and the secondary particles are quasi-spherical, and the interior of the secondary particles has uniformly distributed pores.

[0087] In one embodiment, the polycrystalline structure oxide precursor satisfies at least one of the following conditions:

[0088] (1) The D 50 of the primary particles is 0.1 μm to 1 μm;

[0089] (2) The D50 is from 5 μm to 20 μm;

[0090] (3) The D of the secondary particles max is from 30 μm to 50 μm;

[0091] (4) The K of the secondary particles 90 is less than 3;

[0092] (5) The specific surface area of the polycrystalline structure oxide precursor is 7 m 2 / g - 20 m 2 / g;

[0093] (6) The tap density of the polycrystalline structure oxide precursor is 1.1 g / cm 3 -2.5 g / cm 3 .

[0094] The polycrystalline structure oxide precursor satisfying any of the above conditions is beneficial to the entry and diffusion of the sodium source during the sintering preparation of the cathode material. In addition, the morphology of the polycrystalline structure oxide precursor is easily inherited during the sintering of the cathode, which is beneficial to the infiltration of the electrolyte and improves the ion migration rate, thereby improving the rate performance.

[0095] The present invention also provides a cathode material prepared from the polycrystalline structure oxide precursor as described above. Preferably, the cathode material is used as a cathode material for a lithium-ion battery or a sodium-ion battery.

[0096] Using the polycrystalline structure oxide precursor of the present invention to prepare the cathode material can improve the discharge specific capacity, rate performance and stability of the cathode material.

[0097] It should be noted that the preparation method of the cathode material refers to the existing method, and the present invention will not elaborate on this.

[0098] The present invention also provides a secondary battery, including the cathode material as described above. The secondary battery includes, but is not limited to, a sodium-ion battery.

[0099] Specifically, the sodium-ion battery includes a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte. Among them, the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer provided on the surface of the positive electrode current collector, and the positive electrode material layer includes the positive electrode material as described above.

[0100] In one embodiment, the positive electrode material layer further includes a conductive agent and a binder.

[0101] Hereinafter, the polycrystalline structure oxide precursor, its preparation method and application will be further described through the following specific examples.

[0102] Example 1

[0103] Select nickel chloride, copper chloride, ferrous chloride, and manganese chloride as metal salts, and prepare single-metal salt solutions of nickel, copper, iron, and manganese with a concentration of 150 g / L respectively. Then, prepare a mixed-metal salt solution with a concentration of 150 g / L according to the molar ratio of nickel, copper, iron, and manganese of 22:11:33:33. Add 5% polyvinyl alcohol (model PVA-900, molecular size of 32 nm, degree of polymerization of 900) to the mixed-metal salt solution, stir at 75 °C, and after pre-concentration cycling, the solution concentration is purified to 300 g / L. Control the temperature of the roasting furnace at 820 °C and the liquid inlet flow rate at 0.5 m 3 / h, and perform spray pyrolysis to obtain a polycrystalline structure oxide precursor with the chemical general formula Ni 0.22 Cu 0.11 Fe 0.33 Mn 0.33 O2.

[0104] Perform morphology characterization on the polycrystalline structure oxide precursor prepared in this example, and the results are as Figure 2 shown. As can be seen from the SEM image in Figure 2 (a), after adding the binder, the precursor is a polycrystalline structure formed by the aggregation of primary particles, with a spherical morphology and good dispersibility. As can be seen from the CP-SEM image in Figure 2 (b), the interior of the precursor is a solid structure, and there are fewer pores between the primary particles.

[0105] Example 2

[0106] Select nickel sulfate, copper sulfate, ferrous sulfate, and manganese sulfate as metal salts, and prepare single-metal salt solutions of nickel, copper, iron, and manganese with a concentration of 80 g / L respectively. Then, prepare a mixed-metal salt solution with a concentration of 80 g / L according to the molar ratio of nickel, copper, iron, and manganese of 30:5:30:35. Add 2% polyvinyl alcohol (model PVA-600, molecular size of 11 nm, degree of polymerization of 600) to the mixed-metal salt solution, stir at 40 °C, and after pre-concentration cycling, the solution concentration is purified to 200 g / L. Control the temperature of the roasting furnace at 600 °C and the liquid inlet flow rate at 0.2 m 3 / h, and perform spray pyrolysis to obtain a polycrystalline structure oxide precursor with the chemical general formula Ni 0.3 Cu 0.05 Fe 0.3 Mn 0.35 O2.

[0107] Example 3

[0108] Nickel nitrate, cuprous nitrate, and manganese nitrate were selected as metal salts, and single-metal salt solutions of nickel, copper, and manganese with a concentration of 280 g / L were prepared respectively. Then, a mixed-metal salt solution with a concentration of 280 g / L was prepared according to the molar ratio of nickel, copper, and manganese of 4:2:4. 12% polyvinyl alcohol (model PVA-1700, molecular size of 55 nm, degree of polymerization of 1700) was added to the mixed-metal salt solution, and it was stirred at 90 °C. After pre-concentration cycling, the solution concentration was purified to 400 g / L. The temperature of the calcination furnace was controlled at 900 °C, and the liquid inlet flow rate was 1.0 m 3 / h, and spray pyrolysis was carried out to obtain a polycrystalline structure oxide precursor with the chemical general formula Ni 0.4 Cu 0.2 Mn 0.4 O2.

[0109] Example 4

[0110] Nickel chloride, copper chloride, ferrous chloride, and manganese chloride were selected as metal salts, and single-metal salt solutions of nickel, copper, iron, and manganese with a concentration of 150 g / L were prepared respectively. Then, a mixed-metal salt solution with a concentration of 150 g / L was prepared according to the molar ratio of nickel, copper, iron, and manganese of 32:8:20:40. 5% cellulose was added to the mixed-metal salt solution, and it was stirred at 75 °C. After pre-concentration cycling, the solution concentration was purified to 280 g / L. The temperature of the calcination furnace was controlled at 760 °C, and the liquid inlet flow rate was 0.56 m 3 / h, and spray pyrolysis was carried out to obtain a polycrystalline structure oxide precursor with the chemical general formula Ni 0.32 Cu 0.08 Fe 0.2 Mn 0.4 O2.

[0111] Example 5

[0112] Nickel chloride, copper chloride, ferrous chloride, and manganese chloride were selected as metal salts, and single-metal salt solutions of nickel, copper, iron, and manganese with a concentration of 150 g / L were prepared respectively. Then, a mixed-metal salt solution with a concentration of 150 g / L was prepared according to the molar ratio of nickel, copper, iron, and manganese of 2:3:3:2. 3% sodium polyacrylate (model PVA-1300, molecular size of 43 nm, degree of polymerization of 1300) and 4% starch were added to the mixed-metal salt solution, and it was stirred at 75 °C. After pre-concentration cycling, the solution concentration was purified to 300 g / L. The temperature of the calcination furnace was controlled at 800 °C, and the liquid inlet flow rate was 0.5 m 3 / h, and spray pyrolysis was carried out to obtain a polycrystalline structure oxide precursor with the chemical general formula Ni 0.2 Cu 0.3 Fe 0.3 Mn 0.2 O2.

[0113] Example 6

[0114] Example 6 is different from Example 1 in that a mixed metal salt solution with a concentration of 150 g / L is prepared according to the molar ratio of nickel, copper, and iron of 40:20:40. The obtained polycrystalline structure oxide precursor has a chemical general formula of Ni 0.4 Cu 0.2 Fe 0.4 O2.

[0115] Example 7

[0116] Example 7 is different from Example 1 in that a mixed metal salt solution with a concentration of 150 g / L is prepared according to the molar ratio of copper, iron, and manganese of 90:5:5. The obtained polycrystalline structure oxide precursor has a chemical general formula of Cu 0.9 Fe 0.05 Mn 0.05 O2.

[0117] Example 8

[0118] Example 8 is different from Example 1 in that a mixed metal salt solution with a concentration of 150 g / L is prepared according to the molar ratio of nickel and copper of 35:65. The obtained polycrystalline structure oxide precursor has a chemical general formula of Ni 0.35 Cu 0.65 O2.

[0119] Example 9

[0120] Example 9 is different from Example 1 in that polyvinyl alcohol (model PVA-2500) with a molecular size of 115 nm and a degree of polymerization of 2500 is used.

[0121] Example 10

[0122] Example 10 is different from Example 1 in that polyvinyl alcohol (model PVA-2100) with a molecular size of 58.7 nm and a degree of polymerization of 2100 is used.

[0123] Comparative Example 1

[0124] Comparative Example 1 is different from Example 1 in that no polyvinyl alcohol is added.

[0125] The morphology of the oxide precursor prepared in this comparative example was characterized, and the results are as Figure 3 shown. It can be seen from the Figure 3 SEM image that the obtained oxide precursor is a single crystal structure and its morphology is spherical or quasi-spherical primary small particles under the condition of not adding a binder.

[0126] Comparative Example 2

[0127] Comparative Example 2 is different from Example 1 in that the amount of polyvinyl alcohol used is 0.5%.

[0128] The oxide precursor prepared in this comparative example was characterized in terms of morphology, and the results are as follows Figure 4 shown. From Figure 4 the SEM image of (a), it can be seen that a small amount of binder can also produce a polycrystalline structure, but there are some particles that do not agglomerate into spheres, which is due to too little binder and the binding effect is not obvious. From Figure 4 the CP-SEM image of (b), it can be seen that there are pores distributed inside the precursor, and the tap density and specific surface area are poor.

[0129] Comparative Example 3

[0130] The difference between Comparative Example 3 and Example 1 is that the amount of polyvinyl alcohol used is 15%.

[0131] The oxide precursor prepared in this comparative example was characterized in terms of morphology, and the results are as follows Figure 5 shown. From Figure 5 the SEM image of (a), it can be seen that an excessive amount of binder will cause the solvent to start evaporating inside the particles, forming donut-shaped particles instead of spherical particles. From Figure 5 the CP-SEM image of (b), it can also be seen that there are obvious depressions inside the precursor.

[0132] Comparative Example 4

[0133] The difference between Comparative Example 4 and Example 1 is that nickel chloride metal solution was not added, a copper-iron-manganese ternary metal mixed solution was prepared according to the molar ratio of copper, iron, and manganese of 2:3:5, and polyvinyl alcohol was not added.

[0134] The oxide precursor prepared in this comparative example was characterized in terms of morphology, and the results are as follows Figure 6 shown. From Figure 6 the SEM image, it can be seen that the prepared precursor is a single crystal structure, its morphology is an octahedron-like structure, and the primary particle sizes are not very uniform, and there is agglomeration between some particles.

[0135] Comparative Example 5

[0136] The difference between Comparative Example 5 and Example 1 is that an equal amount of silicate ester glue was used instead of polyvinyl alcohol.

[0137] The test results of the precursors prepared in Examples 1 to 10 and Comparative Examples 1 to 5 are shown in Table 1.

[0138] Table 1

[0139]

[0140] Application Example

[0141] The precursors prepared in Examples 1 to 10 and Comparative Examples 1 to 5 were mixed with sodium carbonate at a molar ratio of 1:1, and then placed in a muffle furnace. Under an air atmosphere, the temperature was raised to 900 °C at a heating rate of 5 °C / min, sintered at a constant temperature for 15 h, naturally cooled, pulverized, and sieved to obtain the cathode material. The cathode material was used to prepare a cathode sheet and assembled into a sodium-ion battery for performance testing.

[0142] The performance test conditions were: discharge specific capacity under a voltage condition of 2 V - 4.15 V; capacity retention rate measured after 70 cycles; rate performance test was carried out at 0.1C, 0.2C, 0.5C, 1C, and 3C. The test results are shown in Table 2 and Figures 7 to 9 as follows.

[0143] Table 2

[0144]

[0145]

[0146] According to Table 2 and Figures 7 to 9 it can be seen that compared with Example 1, the rate performance of Comparative Example 1 is significantly reduced, indicating that the polycrystalline structure formed after adding the binder can effectively improve the electrochemical performance; the discharge specific capacity and capacity retention rate of Comparative Example 2 are also reduced, indicating that adding a small amount of binder cannot form a polycrystalline structure and cannot improve the electrochemical performance; the discharge specific capacity and capacity retention rate of Comparative Example 3 are also reduced, indicating that adding an excessive amount of binder will not only not improve the performance, but also form a donut structure, resulting in a decrease in volume capacity and easy fragmentation of the structure during charge and discharge, leading to poor cycle stability; Comparative Example 4 did not use a binder, and the copper oxide-free precursor formed was a single crystal structure and there was an agglomeration problem; Comparative Example 5 used an inorganic binder, silicate glue, and due to the reaction of metal ions with the silicon-oxygen bonds in the silicate glue, the curing was affected and the bonding effect was poor.

[0147] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0148] The above-described embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention patent should be subject to the appended claims.

Claims

1. A method for preparing a polycrystalline structure oxide precursor, characterized in that, The preparation method includes the following steps: Prepare a mixed metal salt solution; Heat and mix the mixed metal salt solution with a binder to obtain a first solution, wherein the binder is selected from synthetic organic materials and / or natural polymer materials, and the dosage of the binder is 2%-12% of the mass of the first solution; The first solution is pre-concentrated and spray pyrolyzed to obtain a polycrystalline structure oxide precursor.

2. The preparation method of the polycrystalline structure oxide precursor according to claim 1, characterized in that The synthetic organic material satisfies at least one of the following conditions: (1) The molecular size of the synthetic organic material is 1 nm - 60 nm; (2) The degree of polymerization of the synthetic organic material is 200 - 2000.

3. The preparation method of the polycrystalline structure oxide precursor according to claim 1, characterized in that, For every 10 g / L increase in the concentration of the mixed metal salt solution, the proportion of the binder in the first solution increases by 0.1% - 2.5%.

4. The preparation method of the polycrystalline structure oxide precursor according to claim 1, wherein The binder satisfies at least one of the following conditions: (1) The binder is selected from a mixture of synthetic organic materials and natural polymer materials; (2) The dosage of the binder is 3% - 8% of the mass of the first solution; (3) The synthetic organic material is selected from at least one of polyethylene glycol, polyvinyl alcohol, polyvinyl butyral, sodium polyacrylate, or polyurethane; (4) The natural polymer material is selected from at least one of lignin, cellulose, starch, or chitosan.

5. The preparation method of the polycrystalline structure oxide precursor according to claim 1, wherein, The mixed metal salt solution is prepared according to the stoichiometric ratio of Cu a M 1-a O2, where M is selected from at least one of Ni, Fe, or Mn, and 0.1 ≤ a ≤ 0.

9.

6. The preparation method of the polycrystalline structure oxide precursor according to claim 5, characterized in that, The mixed metal salt solution satisfies at least one of the following conditions: (1) The total concentration of metal ions in the mixed metal salt solution is 80 g / L - 280 g / L; (2) In the mixed metal salt solution, the copper salt is selected from at least one of cuprous chloride, copper chloride, cuprous sulfate, copper sulfate, cuprous nitrate, or copper nitrate; (3) When M is selected as Ni, in the mixed metal salt solution, the nickel salt is selected from at least one of nickel chloride, nickel sulfate, or nickel nitrate; (4) When M is selected as Fe, in the mixed metal salt solution, the iron salt is selected from at least one of ferrous chloride, ferric chloride, ferrous sulfate, ferric sulfate, ferrous nitrate, or ferric nitrate; (5) When M is selected as Mn, in the mixed metal salt solution, the manganese salt is selected from at least one of manganese chloride, manganese sulfate, or manganese nitrate.

7. The preparation method of the polycrystalline structure oxide precursor according to claim 1, wherein In the step of heating and mixing the mixed metal salt solution with the binder, the temperature is 40°C - 90°C, the stirring speed is 100 r / min - 300 r / min, and the time is 0.5 h - 3 h.

8. The method for preparing the polycrystalline structure oxide precursor according to claim 1, wherein, The step of pre-concentrating and spray pyrolyzing the first solution satisfies at least one of the following conditions: (1) The total concentration of metal ions after pre-concentration of the first solution is 200 g / L - 400 g / L; (2) During the spray pyrolysis process, the liquid feeding flow rate of the first solution is 0.2 m 3 / h - 1.0 m 3 / h; (3) The temperature of the spray pyrolysis is 600°C - 900°C.

9. A polycrystalline structure oxide precursor obtained by the preparation method of the polycrystalline structure oxide precursor according to any one of claims 1-8, characterized in that, The polycrystalline structure oxide precursor is secondary particles formed by the aggregation of primary particles.

10. The polycrystalline structure oxide precursor according to claim 9, wherein The polycrystalline structure oxide precursor satisfies at least one of the following conditions: (1) The D of the primary particles 50 is from 0.1 μm to 1 μm; (2) The D of the secondary particles 50 is from 5 μm to 20 μm; (3) The D of the secondary particles max is from 30 μm to 50 μm; (4) The K of the secondary particles 90 is less than 3; (5) The specific surface area of the polycrystalline structure oxide precursor is 7 m 2 / g - 20 m 2 / g; (6) The tapped density of the polycrystalline structure oxide precursor is 1.1 g / cm 3 - 2.5 g / cm 3 .

11. A positive electrode material prepared from the polycrystalline structure oxide precursor as claimed in claim 9 or 10.

12. A positive electrode sheet, characterized in that, It includes a positive electrode current collector and a positive electrode material layer provided on the surface of the positive electrode current collector, and the positive electrode material layer includes the positive electrode material as claimed in claim 11.

13. A secondary battery, characterized in that, It includes the positive electrode sheet as claimed in claim 12.

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