Positive electrode material and preparation method and application thereof
By designing a multi-layer structure of positive electrode materials, including a core, a buffer layer and a coating layer, the rate performance and cycle stability problems of high-nickel ternary polycrystalline positive electrode materials were solved, and the performance of lithium-ion batteries with high energy density and long cycle life was achieved.
Patent Information
- Application Number
- CN202511019298.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-23
- Publication Date
- 2025-10-28
AI Technical Summary
High-nickel ternary polycrystalline positive electrode materials have poor rate performance in actual applications and are prone to stress, strain and microcracks during the cycle process, resulting in poor cycle performance. Existing technologies make it difficult to simultaneously improve their rate performance and cycle stability.
A multi-layer structured positive electrode material design is adopted, including a core, a buffer layer and a coating layer. The core is composed of ternary positive electrode active material particles A, the buffer layer is composed of ternary positive electrode active material particles B and dielectric piezoelectric material A, and the coating layer is composed of dielectric piezoelectric material B. The dielectric constant ε>1000 and the piezoelectric constant d>100pC/N of the dielectric piezoelectric material A are controlled to buffer stress and promote lithium ion transmission.
It improves the rate performance and cycle stability of lithium-ion batteries, inhibits the generation of microcracks, enhances the mechanical properties and safety of materials, and achieves high energy density and long cycle life.
Smart Images
Figure CN120854527A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of cathode material technology, specifically relating to a cathode material, its preparation method, and its application. Background Technology
[0002] With the development of emerging fields such as electric vehicles, power tools, and smart grids, the demand for high energy density, high power density, and long cycle life of lithium-ion batteries is becoming increasingly urgent. High-nickel ternary polycrystalline cathode materials have become a research hotspot in the field of lithium-ion batteries due to their high energy density and long cycle life, and they have broad application prospects, especially in electric vehicles and renewable energy storage systems.
[0003] Despite the many advantages of high-nickel ternary polycrystalline cathode materials, they still face some challenges in practical applications, such as poor rate performance and poor cycle performance caused by stress, strain and microcracks generated during cycling, which to some extent limit their further application.
[0004] In current research on high-nickel ternary polycrystalline cathode materials, designing by doping with magnesium ions can improve their rate performance to some extent, but it is difficult to solve the problems of stress, strain and microcracks generated during cycling. While introducing a second phase material during the process of granulation to synthesize secondary particles from primary particles can effectively suppress the pulverization of secondary particles along the interface between primary particles in lithium-ion battery cathode materials to some extent, the resulting cathode material has poor rate performance, and the loss of electrochemical performance is not negligible. Summary of the Invention
[0005] Therefore, the technical problem to be solved by the present invention is to overcome the shortcomings of the prior art in which it is difficult to simultaneously improve rate performance, reduce microcracks, and improve cycle performance of high-nickel ternary polycrystalline cathode materials, thereby providing a cathode material, its preparation method, and its application.
[0006] To this end, the present invention provides the following technical solution.
[0007] In a first aspect, this application provides a cathode material, including polycrystalline ternary cathode active material particles and a coating layer disposed on the surface of the polycrystalline ternary cathode active material particles; the polycrystalline ternary cathode active material particles include a core and a buffer layer from the inside out;
[0008] The core includes ternary positive electrode active material particles A;
[0009] The buffer layer comprises ternary positive electrode active material particles B and dielectric piezoelectric material A; the dielectric constant ε of the dielectric piezoelectric material A is greater than 1000, and the piezoelectric constant d is greater than 100 pC / N;
[0010] The coating layer includes a dielectric piezoelectric material B.
[0011] In one possible implementation, the D50 particle size of the secondary particles of the polycrystalline ternary cathode active material particles is 5-15 μm, and can be selected as 10-12 μm.
[0012] In one possible implementation, the average particle size of the primary particles of the ternary positive electrode active material B is 10-500 nm.
[0013] Secondary particles are formed by the aggregation of primary particles.
[0014] The D50 particle size of the secondary particles of the polycrystalline ternary cathode active material particles was measured by a laser particle size analyzer.
[0015] The average value of the primary particles of the ternary positive electrode active material B
[0016] The particle size was measured using a scanning electron microscope.
[0017] In one possible implementation, the chemical formula of the ternary cathode active material particle A is LiNi. x1 Co y1 Mn z1 M 1-x1-y1-z1 O2, where 0.8≤x1≤0.95, x1+y1+z1≤1, and M includes one or more of Al, Mg, Ti, W, Fe, Mo, Zr, Nb, Zn, La, Ca, Sr, Sn, Sb, Si, Ba, Y, Ta and Ce;
[0018] In one possible implementation, 0.85 ≤ x1 ≤ 0.9, and M contains Mg, Ti, Nb, and Mo;
[0019] In one possible implementation, the chemical formula of the ternary cathode active material particle B is LiNi. x2 Co y2 Mn z2 K 1-x2-y2-z2 O2, where 0.8≤x2≤0.95, x2+y2+z2≤1, and K includes one or more of Al, Mg, Ti, W, Fe, Mo, Zr, Nb, Zn, La, Ca, Sr, Sn, Sb, Si, Ba, Y, Ta and Ce;
[0020] In one possible implementation, 0.85 ≤ x2 ≤ 0.9, and K contains Mg, Ti, Nb, and Mo;
[0021] In one possible implementation, the ternary positive electrode active material particle A and the ternary positive electrode active material particle B may have the same or different chemical formulas.
[0022] In one possible implementation, the D50 particle size of the core is 1–4 μm, optionally 2.5–3.5 μm.
[0023] In one possible implementation, the thickness of the buffer layer is 4–15 μm, optionally 8–10 μm;
[0024] In one possible implementation, the dielectric piezoelectric material A comprises one or more of barium titanate, bismuth titanate, lanthanum titanate, lead zirconate titanate, or lead magnesium niobium zirconate titanate.
[0025] In one possible implementation, the D50 particle size of the dielectric piezoelectric material A is 10-500 nm, and can be selected as 100-300 nm;
[0026] In one possible implementation, the molar ratio of ternary positive electrode active material particles B to dielectric voltelectroelectric material A in the buffer layer is (20-2000):1, and can be selected as (50-500):1.
[0027] In one possible implementation, the dielectric piezoelectric material B comprises one or more of barium titanate, bismuth titanate, lanthanum titanate, lead zirconate titanate, or lead magnesium niobium zirconate titanate.
[0028] In one possible implementation, the D50 particle size of the dielectric piezoelectric material B is 10-500 nm, and can be selected as 100-300 nm;
[0029] In one possible implementation, the mass of the covering layer is 0.5wt% to 5wt% of the total mass of the core and buffer layers, and optionally 1wt% to 1.5wt%.
[0030] In one possible implementation, the dielectric constant ε of the dielectric piezoelectric material B is greater than 1000, and the piezoelectric constant d is greater than 100 pC / N.
[0031] In one possible implementation, the dielectric volt-electric material B may be the same as or different from the dielectric volt-electric material A.
[0032] Secondly, this application provides a method for preparing a cathode material, comprising the following steps:
[0033] S1. Preparation of precursor crystal nuclei;
[0034] S2. The precursor crystal nuclei are fed into a coprecipitation reactor. A second metal salt solution, a second alkaline solution, a second complex solution, and a dispersion of dielectric and electrostatic material A are added to the coprecipitation reactor. The pH2 and temperature T2 are controlled to react and obtain the precursor.
[0035] S3. The precursor is mixed with a lithium source and dielectric piezoelectric material B, and then subjected to a first sintering to obtain a precursor pre-sintered material.
[0036] S4. The precursor pre-burned material is subjected to a second sintering to obtain the cathode material.
[0037] The core is formed by the second sintering of the precursor crystal nucleus in the precursor.
[0038] In one possible implementation, S1 includes: adding a first metal salt solution, a first alkaline solution and a first complex solution to a coprecipitation reactor, controlling pH1 and temperature T1, and reacting in the reactor to obtain the precursor crystal nucleus;
[0039] In one possible implementation, the pH1 is 10 to 12;
[0040] In one possible implementation, T1 is 45–60°C, and can be selected as 55°C;
[0041] In one possible implementation, the D50 particle size of the precursor nucleus is 1–4 μm, and can be selected as 2.5–3.5 μm;
[0042] In one possible implementation, during the reaction in S1, the stirring speed is controlled to be 500-1500 rpm, and can be selected as 1000 rpm.
[0043] In one possible implementation, the first metal salt in the first metal salt solution includes one or more of the following: sulfate, acetate, nitrate, oxalate, and chloride salt corresponding to each metal, and may be selected as sulfate;
[0044] In one possible implementation, the first alkaline solution includes one or more of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution, or ammonium carbonate solution, and may be selected as sodium hydroxide solution;
[0045] In one possible implementation, the first complex solution comprises one or more of ammonia, oxalic acid solution, or citric acid solution, with ammonia being an option.
[0046] In one possible implementation, the total molar concentration of the metal element in the first metal salt solution is 1 to 5 mol / L, and can be selected as 2 mol / L;
[0047] In one possible implementation, the concentration of the first alkaline solution is 5–12 mol / L, and optionally 8–10 mol / L;
[0048] In one possible implementation, the concentration of the first complex solution is 5–15 mol / L, optionally 10–13 mol / L.
[0049] In one possible implementation, in S1, after the raw materials react for a period of time, solid-liquid separation is performed, and the solid product is washed, filtered, dried, crushed and sieved to obtain precursor crystal nuclei.
[0050] In one possible implementation, the pH2 is 10 to 12;
[0051] In one possible implementation, T2 is 45–60°C, and can be selected as 55°C;
[0052] In one possible implementation, during the reaction in S2, the stirring speed is controlled to be 600-1500 rpm, and optionally 1000 rpm.
[0053] In one possible implementation, the second metal salt in the second metal salt solution includes one or more of the following: sulfate, acetate, nitrate, oxalate, and chloride salt corresponding to each metal, and may be selected as sulfate;
[0054] In one possible implementation, the second alkaline solution includes one or more of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution, or ammonium carbonate solution, and may be selected as sodium hydroxide solution;
[0055] In one possible implementation, the second complex solution comprises one or more of ammonia, oxalic acid solution, or citric acid solution, with ammonia being an option.
[0056] In one possible implementation, the total molar concentration of the metal element in the second metal salt solution is 1 to 5 mol / L, and can be selected as 2 mol / L;
[0057] In one possible implementation, the concentration of the second alkaline solution is 5–12 mol / L, and optionally 8–10 mol / L;
[0058] In one possible implementation, the concentration of the second complex solution is 5–15 mol / L, optionally 10–13 mol / L;
[0059] In one possible implementation, the solid-liquid mass ratio of the dielectric electrostatic material A dispersion is 1:20 to 1:100;
[0060] In one possible implementation, the flow rate ratio of the metal salt solution to the dispersion of dielectric electrostatic material A is (3-20):1.
[0061] In one possible implementation, in step S3, the lithium source includes one or more of lithium hydroxide (LiOH) and lithium carbonate (Li2CO3), and may be selected as LiOH;
[0062] In one possible implementation, in step S3, the ratio of the molar amount of Li element in the lithium source to the total molar amount of metal element in the precursor is 1.00 to 1.15, and can be selected as 1.03 to 1.08.
[0063] In one possible implementation, in step S3, the temperature of the first sintering is 450–650°C, optionally 500–600°C; and the sintering time is 5–10 hours.
[0064] In one possible implementation, in S3, the heating rate of the first sintering is 1 to 10 °C / min, and can be selected as 2 to 5 °C / min;
[0065] In one possible implementation, in S3, the atmosphere for the first sintering is either air or pure oxygen, and can be selected as pure oxygen.
[0066] In one possible implementation, in step S4, the second sintering temperature is 750–950°C, optionally 800–850°C; the sintering time is 10–24 hours.
[0067] In one possible implementation, in step S4, the heating rate of the second sintering is 1 to 10 °C / min, and can be selected as 2 to 5 °C / min;
[0068] In one possible implementation, in S3, the atmosphere for the second sintering is a pure oxygen atmosphere.
[0069] Thirdly, this application provides a positive electrode sheet, including the aforementioned positive electrode material or a positive electrode material prepared according to the aforementioned preparation method.
[0070] Fourthly, this application provides a lithium-ion secondary battery, including the aforementioned positive electrode. The technical solution of this invention has the following advantages:
[0071] 1. The cathode material of this application includes polycrystalline ternary cathode active material particles and a coating layer disposed on the surface of the polycrystalline ternary cathode active material particles; the polycrystalline ternary cathode active material particles include a core and a buffer layer from the inside out; the core includes ternary cathode active material particles A; the buffer layer includes ternary cathode active material particles B and dielectric piezoelectric material A; the dielectric constant ε of the dielectric piezoelectric material A is >1000, and the piezoelectric constant d is >100pC / N; the coating layer includes dielectric piezoelectric material B.
[0072] The cathode material of this application has a multi-level structure. The core ensures the basic structure of the cathode material. The buffer layer includes ternary cathode active material particles B and dielectric piezoelectric material A. The dielectric constant ε of dielectric piezoelectric material A is greater than 1000, and the piezoelectric constant d is greater than 100 pC / N. Dielectric piezoelectric material A is a high dielectric piezoelectric material. The high dielectric piezoelectric material introduced into the buffer layer can promote the internal transport process of lithium ions and improve the rate performance of the material. Moreover, the structural changes and stress generation inside the cathode material mainly come from the internal deintercalation and intercalation of lithium ions. When the lithium ion deintercalation and intercalation in a certain local area inside the cathode material becomes excessive and begins to cause structural changes and generate internal stress, dielectric piezoelectric material A will generate an internal reverse electric field to slow down the further deintercalation and intercalation process of local lithium ions, thereby preventing the structural deterioration of the area and thus macroscopically suppressing the generation of internal microcracks. The buffer layer acts as a stress buffer, suppressing the generation of microcracks during cycling, ensuring the structural stability of the polycrystalline cathode material during cycling, and improving the cycle life of the cathode material while also achieving higher safety. The dielectric and voltaic material B of the coating layer can form an excellent protective interface on the surface of the buffer layer, improving the mechanical properties of the material while reducing the side reactions between the ternary cathode active material particles A and B and the electrolyte.
[0073] 2. When dielectric pyroelectric material A and dielectric pyroelectric material B are the same, the coating layer can also have excellent compatibility with dielectric pyroelectric material A in the buffer layer, and can build a continuous electric field inside and on the surface of the cathode material, synergistically promoting the lithium ion transport process and further improving the rate performance of the material.
[0074] 3. The method for preparing the cathode material of this application includes the following steps: S1, preparing precursor crystal nuclei; S2, adding the precursor crystal nuclei into a coprecipitation reactor, adding a second metal salt solution, a second alkaline solution, a second complex solution, and a dispersion of dielectric and piezoelectric material A to the coprecipitation reactor, controlling pH2 and temperature T2, and reacting to obtain the precursor; S3, mixing the precursor with a lithium source and dielectric and piezoelectric material B, and performing a first sintering to obtain a precursor pre-sintered material; S4, performing a second sintering of the precursor pre-sintered material to obtain the cathode material.
[0075] The synthesis method used in this invention is simple and easy to implement, and is fully compatible with the preparation process of industrial polycrystalline cathode materials. In addition, the thickness of the core and buffer layer can be controlled during the precursor synthesis process, which can meet the application requirements in different scenarios and effectively improve the rate performance, cycle stability and safety of lithium-ion batteries. Attached Figure Description
[0076] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0077] Figure 1 This is a schematic diagram of the positive electrode material structure.
[0078] Figure label:
[0079] 1-Kernel; 2-Buffer layer; 3-Overlay layer. Detailed Implementation
[0080] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.
[0081] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.
[0082] Example 1
[0083] This embodiment provides a method for preparing a cathode material, the method comprising the following steps:
[0084] (1) Solution preparation: Mix NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O, MgSO4·7H2O, TiOSO4, and (NH4)6Mo7O. 24 Prepare a metal salt solution with a total molar concentration of 2 mol / L by mixing Nb(HC2O4)5 with Ni:Co:Mn:Mg:Ti:Mo:Nb = 88:3:3:2:2:1:1; prepare a 10 mol / L NaOH solution and a 12.5 mol / L ammonia solution for later use; add NaOH and ammonia to pure water to control its pH to 12 and ammonia value to 5 g / L, and record this as base solution 1; add NaOH and ammonia to pure water to control its pH to 11 and ammonia value to 5 g / L, and record this as base solution 2.
[0085] (2) Preparation of precursor crystal nuclei: Add 2L of bottom liquid 1 to the reaction vessel, introduce nitrogen gas, and introduce the prepared metal salt solution, NaOH solution and ammonia solution into the reaction vessel at a speed of 1000rpm. The flow rate of the metal salt solution is 0.6L / h and the flow rate of the ammonia solution is 0.05L / h. React at pH 11 and temperature of 55℃ until the D50 particle size of the precursor reaches 3μm. Separate the solid and liquid, and obtain the precursor crystal nuclei by washing, filtering, drying and crushing the solid product.
[0086] (3) Precursor growth: Add the precursor nuclei prepared in step (2) and 2L of bottom liquid 2 to the reactor, introduce nitrogen gas, and introduce the prepared metal salt solution, NaOH solution, ammonia solution and barium titanate dispersion (the solid-liquid mass ratio of barium titanate dispersion is 1:50) into the reactor at a speed of 1000 rpm. The flow rate ratio of metal salt solution to barium titanate dispersion is 10:1, the flow rate of metal salt solution is 0.6L / h, and the flow rate of ammonia solution is 0.05L / h. React under the conditions of pH 11 and temperature 55℃ until the D50 particle size of the precursor reaches 10μm. Separate the solid and liquid, and obtain precursor particles with hierarchical structure after washing, filtering, drying and crushing and sieving the solid product.
[0087] (4) Precursor pre-calcination: Precursor particles and LiOH powder were weighed according to the ratio of Li molar amount to total molar amount of metal elements in the precursor = 1.08, and 1 wt% of barium titanate was weighed in the precursor particles. They were thoroughly mixed and pre-calcined at 550℃ for 6 hours in a pure oxygen atmosphere at a heating rate of 2℃ / min. After the pre-calcination was completed, the precursor pre-calcined material was obtained after crushing and sieving.
[0088] (5) Preparation of cathode material: The precursor pre-calcined material was sintered at 850℃ for 15h in a pure oxygen atmosphere, with a heating rate of 2℃ / min. After the sintering was completed, the high-nickel polycrystalline cathode material was obtained by crushing and sieving.
[0089] A schematic diagram of the cathode material is shown below. Figure 1 As shown, it includes kernel 1, buffer layer 2 and wrapping layer 3.
[0090] Example 2
[0091] This embodiment provides a method for preparing a cathode material, including the following steps:
[0092] (1) Solution preparation: Prepare a 2 mol / L metal salt solution by mixing NiSO4·6H2O, CoSO4·7H2O and MnSO4·H2O in a molar ratio of Ni:Co:Mn = 88:6:6; prepare a 10 mol / L NaOH solution and a 12.5 mol / L ammonia solution for later use; add NaOH and ammonia to pure water to control its pH to 12 and ammonia value to 5 g / L, and record it as base solution 1; add NaOH and ammonia to pure water to control its pH to 11 and ammonia value to 5 g / L, and record it as base solution 2.
[0093] (2) Preparation of precursor crystal nuclei: Add 2L of bottom liquid 1 to the reaction vessel, introduce nitrogen gas, and introduce the prepared metal salt solution, NaOH solution and ammonia solution into the reaction vessel at a speed of 1000rpm. The flow rate of the metal salt solution is 0.6L / h and the flow rate of the ammonia solution is 0.05L / h. React at pH 11 and temperature of 55℃ until the D50 particle size of the precursor reaches 3μm. Separate the solid and liquid, and obtain the precursor crystal nuclei by washing, filtering, drying and crushing the solid product.
[0094] (3) Precursor growth: Add the precursor nuclei prepared in step (2) and 2L of bottom liquid 2 to the reactor, introduce nitrogen gas, and introduce the prepared metal salt solution, NaOH solution, ammonia solution and barium titanate dispersion (the solid-liquid mass ratio of barium titanate dispersion is 1:50) into the reactor at a speed of 1000 rpm. The flow rate ratio of metal salt solution to barium titanate dispersion is 10:1, the flow rate of metal salt solution is 0.6L / h, and the flow rate of ammonia solution is 0.05L / h. React under the conditions of pH 11 and temperature 55℃ until the D50 particle size of the precursor reaches 10μm. Separate the solid and liquid, and obtain precursor particles with hierarchical structure after washing, filtering, drying and crushing and sieving the solid product.
[0095] (4) Precursor pre-calcination: LiOH powder and precursor particles were weighed according to the ratio of Li molar amount to total molar amount of metal elements in the precursor = 1.08, and 1 wt% of barium titanate was weighed in the precursor particles. They were thoroughly mixed and pre-calcined at 550℃ for 6 hours under a pure oxygen atmosphere with a heating rate of 2℃ / min. After the pre-calcination was completed, the precursor pre-calcined material was obtained by crushing and sieving.
[0096] (5) Preparation of cathode material: The precursor pre-calcined material was sintered at 850℃ for 15h in a pure oxygen atmosphere, with a heating rate of 2℃ / min. After the sintering was completed, the high-nickel polycrystalline cathode material was obtained by crushing and sieving.
[0097] Example 3
[0098] This embodiment provides a method for preparing a cathode material, including the following steps:
[0099] (1) Solution preparation: Mix NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O, MgSO4·7H2O, TiOSO4, and (NH4)6Mo7O. 24 Prepare a 2 mol / L metal salt solution of Nb(HC2O4)5 according to the molar ratio of Ni:Co:Mn:Mg:Ti:Mo:Nb=88:3:3:2:2:1:1; prepare a 10 mol / L NaOH solution and a 12.5 mol / L ammonia solution for later use; add NaOH and ammonia to pure water to control its pH to 12 and ammonia value to 5 g / L, and record this as base solution 1; add NaOH and ammonia to pure water to control its pH to 11 and ammonia value to 5 g / L, and record this as base solution 2.
[0100] (2) Preparation of precursor crystal nuclei: Add 2L of bottom liquid 1 to the reaction vessel, introduce nitrogen gas, and introduce the prepared metal salt solution, NaOH solution and ammonia solution into the reaction vessel at a speed of 1000rpm. The flow rate of the metal salt solution is 0.6L / h and the flow rate of the ammonia solution is 0.05L / h. React at pH 11 and temperature of 55℃ until the D50 particle size of the precursor reaches 3μm. Separate the solid and liquid, and obtain the precursor crystal nuclei by washing, filtering, drying and crushing the solid product.
[0101] (3) Precursor growth: Add the precursor nuclei prepared in step (2) and 2L of bottom liquid 2 to the reactor, introduce nitrogen gas, and introduce the prepared metal salt solution, NaOH solution, ammonia solution and barium titanate dispersion (the solid-liquid mass ratio of barium titanate dispersion is 1:100) into the reactor at a speed of 1000 rpm. The flow rate ratio of metal salt solution to barium titanate dispersion is 10:1, the flow rate of metal salt solution is 0.6L / h, and the flow rate of ammonia solution is 0.05L / h. React under the conditions of pH 11 and temperature 55℃ until the D50 particle size of the precursor reaches 10μm. Separate the solid and liquid, and obtain precursor particles with hierarchical structure after washing, filtering, drying and crushing and sieving the solid product.
[0102] (4) Precursor pre-calcination: Precursor particles and LiOH powder were weighed according to the ratio of Li molar amount to total molar amount of metal elements in the precursor = 1.08, and 1 wt% of barium titanate was weighed in the precursor particles. They were thoroughly mixed and pre-calcined at 550℃ for 6 hours in a pure oxygen atmosphere at a heating rate of 2℃ / min. After the pre-calcination was completed, the precursor pre-calcined material was obtained after crushing and sieving.
[0103] (5) Preparation of cathode material: The precursor pre-calcined material was sintered at 850℃ for 15h in a pure oxygen atmosphere, with a heating rate of 2℃ / min. After the sintering was completed, the high-nickel polycrystalline cathode material was obtained by crushing and sieving.
[0104] Example 4
[0105] This embodiment provides a method for preparing a cathode material, including the following steps:
[0106] (1) Solution preparation: Mix NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O, MgSO4·7H2O, TiOSO4, and (NH4)6Mo7O. 24 Prepare a 2 mol / L metal salt solution of Nb(HC2O4)5 according to the molar ratio of Ni:Co:Mn:Mg:Ti:Mo:Nb=88:3:3:2:2:1:1; prepare a 10 mol / L NaOH solution and a 12.5 mol / L ammonia solution for later use; add NaOH and ammonia to pure water to control its pH to 12 and ammonia value to 5 g / L, and record this as base solution 1; add NaOH and ammonia to pure water to control its pH to 11 and ammonia value to 5 g / L, and record this as base solution 2.
[0107] (2) Preparation of precursor crystal nuclei: Add 2L of bottom liquid 1 to the reaction vessel, introduce nitrogen gas, and introduce the prepared metal salt solution, NaOH solution and ammonia solution into the reaction vessel at a speed of 1000rpm. The flow rate of the metal salt solution is 0.6L / h and the flow rate of the ammonia solution is 0.05L / h. React at pH 11 and temperature of 55℃ until the D50 particle size of the precursor reaches 3μm. Separate the solid and liquid, and obtain the precursor crystal nuclei by washing, filtering, drying and crushing the solid product.
[0108] (3) Precursor growth: Add the precursor nuclei prepared in step (2) and 2L of bottom liquid 2 to the reactor, introduce nitrogen gas, and introduce the prepared metal salt solution, NaOH solution, ammonia solution and barium titanate dispersion (the solid-liquid mass ratio of barium titanate dispersion is 1:20) into the reactor at a speed of 1000 rpm. The flow rate ratio of metal salt solution to barium titanate dispersion is 10:1, the flow rate of metal salt solution is 0.6L / h, and the flow rate of ammonia solution is 0.05L / h. React under the conditions of pH 11 and temperature 55℃ until the D50 particle size of the precursor reaches 10μm. Separate the solid and liquid, and obtain precursor particles with hierarchical structure after washing, filtering, drying and crushing and sieving the solid product.
[0109] (4) Precursor pre-calcination: Precursor particles and LiOH powder were weighed according to the ratio of Li molar amount to total molar amount of metal elements in the precursor = 1.08, and 1 wt% of barium titanate was weighed in the precursor particles. They were thoroughly mixed and pre-calcined at 550℃ for 6 hours in a pure oxygen atmosphere at a heating rate of 2℃ / min. After the pre-calcination was completed, the precursor pre-calcined material was obtained after crushing and sieving.
[0110] (5) Preparation of cathode material: The precursor pre-calcined material was sintered at 850℃ for 15h in a pure oxygen atmosphere, with a heating rate of 2℃ / min. After the sintering was completed, the high-nickel polycrystalline cathode material was obtained by crushing and sieving.
[0111] Example 5
[0112] This embodiment provides a method for preparing a cathode material, including the following steps:
[0113] (1) Solution preparation: Mix NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O, MgSO4·7H2O, TiOSO4, and (NH4)6Mo7O. 24 Prepare a 2 mol / L metal salt solution of Nb(HC2O4)5 according to the molar ratio of Ni:Co:Mn:Mg:Ti:Mo:Nb=88:3:3:2:2:1:1; prepare a 10 mol / L NaOH solution and a 12.5 mol / L ammonia solution for later use; add NaOH and ammonia to pure water to control its pH to 12 and ammonia value to 5 g / L, and record this as base solution 1; add NaOH and ammonia to pure water to control its pH to 11 and ammonia value to 5 g / L, and record this as base solution 2.
[0114] (2) Preparation of precursor crystal nuclei: Add 2L of bottom liquid 1 to the reaction vessel, introduce nitrogen gas, and introduce the prepared metal salt solution, NaOH solution and ammonia solution into the reaction vessel at a speed of 1000rpm. The flow rate of the metal salt solution is 0.6L / h and the flow rate of the ammonia solution is 0.05L / h. React at pH 11 and temperature of 55℃ until the D50 particle size of the precursor reaches 3μm. Separate the solid and liquid, and obtain the precursor crystal nuclei by washing, filtering, drying and crushing the solid product.
[0115] (3) Precursor growth: Add the precursor nuclei prepared in step (2) and 2L of bottom liquid 2 to the reactor, introduce nitrogen gas, and introduce the prepared metal salt solution, NaOH solution, ammonia solution and barium titanate dispersion (the solid-liquid mass ratio of barium titanate dispersion is 1:50) into the reactor at a speed of 1000 rpm. The flow rate ratio of metal salt solution to barium titanate dispersion is 10:1, the flow rate of metal salt solution is 0.6L / h, and the flow rate of ammonia solution is 0.05L / h. React under the conditions of pH 11 and temperature 55℃ until the D50 particle size of the precursor reaches 10μm. Separate the solid and liquid, and obtain precursor particles with hierarchical structure after washing, filtering, drying and crushing and sieving the solid product.
[0116] (4) Precursor pre-calcination: Precursor particles and LiOH powder were weighed according to the ratio of Li molar amount to total molar amount of metal elements in the precursor = 1.08, and 0.5 wt% of barium titanate was weighed in the precursor particles. The mixture was thoroughly mixed and pre-calcined at 550℃ for 6 hours in a pure oxygen atmosphere at a heating rate of 2℃ / min. After the pre-calcination was completed, the precursor pre-calcined material was obtained by crushing and sieving.
[0117] (5) Preparation of cathode material: The precursor pre-calcined material was sintered at 850℃ for 15h in a pure oxygen atmosphere, with a heating rate of 2℃ / min. After the sintering was completed, the high-nickel polycrystalline cathode material was obtained by crushing and sieving.
[0118] Example 6
[0119] This embodiment provides a method for preparing a cathode material, including the following steps:
[0120] (1) Solution preparation: Mix NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O, MgSO4·7H2O, TiOSO4, and (NH4)6Mo7O. 24 Prepare a 2 mol / L metal salt solution of Nb(HC2O4)5 according to the molar ratio of Ni:Co:Mn:Mg:Ti:Mo:Nb=88:3:3:2:2:1:1; prepare a 10 mol / L NaOH solution and a 12.5 mol / L ammonia solution for later use; add NaOH and ammonia to pure water to control its pH to 12 and ammonia value to 5 g / L, and record this as base solution 1; add NaOH and ammonia to pure water to control its pH to 11 and ammonia value to 5 g / L, and record this as base solution 2.
[0121] (2) Preparation of precursor crystal nuclei: Add 2L of bottom liquid 1 to the reaction vessel, introduce nitrogen gas, and introduce the prepared metal salt solution, NaOH solution and ammonia solution into the reaction vessel at a speed of 1000rpm. The flow rate of the metal salt solution is 0.6L / h and the flow rate of the ammonia solution is 0.05L / h. React at pH 11 and temperature of 55℃ until the D50 particle size of the precursor reaches 3μm. Separate the solid and liquid, and obtain the precursor crystal nuclei by washing, filtering, drying and crushing the solid product.
[0122] (3) Precursor growth: Add the precursor nuclei prepared in step (2) and 2L of bottom liquid 2 to the reactor, introduce nitrogen gas, and introduce the prepared metal salt solution, NaOH solution, ammonia solution and barium titanate dispersion (the solid-liquid mass ratio of barium titanate dispersion is 1:50) into the reactor at a speed of 1000 rpm. The flow rate ratio of metal salt solution to barium titanate dispersion is 10:1, the flow rate of metal salt solution is 0.6L / h, and the flow rate of ammonia solution is 0.05L / h. React under the conditions of pH 11 and temperature 55℃ until the D50 particle size of the precursor reaches 10μm. Separate the solid and liquid, and obtain precursor particles with hierarchical structure after washing, filtering, drying and crushing and sieving the solid product.
[0123] (4) Precursor pre-calcination: Precursor particles and LiOH powder were weighed according to the ratio of Li molar amount to total molar amount of metal elements in the precursor = 1.08, and 2 wt% of barium titanate was weighed in the precursor particles. They were thoroughly mixed and pre-calcined at 550℃ for 6 hours in a pure oxygen atmosphere at a heating rate of 2℃ / min. After the pre-calcination was completed, the precursor pre-calcined material was obtained after crushing and sieving.
[0124] (5) Preparation of cathode material: The precursor pre-calcined material was sintered at 850℃ for 15h in a pure oxygen atmosphere, with a heating rate of 2℃ / min. After the sintering was completed, the high-nickel polycrystalline cathode material was obtained by crushing and sieving.
[0125] Example 7
[0126] This embodiment provides a method for preparing a cathode material, including the following steps:
[0127] (1) Solution preparation: Mix NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O, MgSO4·7H2O, TiOSO4, and (NH4)6Mo7O. 24 Prepare a 2 mol / L metal salt solution of Nb(HC2O4)5 according to the molar ratio of Ni:Co:Mn:Mg:Ti:Mo:Nb=88:3:3:2:2:1:1; prepare a 10 mol / L NaOH solution and a 12.5 mol / L ammonia solution for later use; add NaOH and ammonia to pure water to control its pH to 12 and ammonia value to 5 g / L, and record this as base solution 1; add NaOH and ammonia to pure water to control its pH to 11 and ammonia value to 5 g / L, and record this as base solution 2.
[0128] (2) Preparation of precursor crystal nuclei: Add 2L of bottom liquid 1 to the reaction vessel, introduce nitrogen gas, and introduce the prepared metal salt solution, NaOH solution and ammonia solution into the reaction vessel at a speed of 1000rpm. The flow rate of the metal salt solution is 0.6L / h and the flow rate of the ammonia solution is 0.05L / h. React at pH 11 and temperature of 55℃ until the D50 particle size of the precursor reaches 3μm. Separate the solid and liquid, and obtain the precursor crystal nuclei by washing, filtering, drying and crushing the solid product.
[0129] (3) Precursor growth: Add the precursor nuclei prepared in step (2) and 2L of bottom liquid 2 to the reactor, introduce nitrogen gas, and introduce the prepared metal salt solution, NaOH solution, ammonia solution and barium titanate dispersion (the solid-liquid mass ratio of barium titanate dispersion is 1:50) into the reactor at a speed of 1000 rpm. The flow rate ratio of metal salt solution to barium titanate dispersion is 10:1, the flow rate of metal salt solution is 0.6L / h, and the flow rate of ammonia solution is 0.05L / h. React under the conditions of pH 11 and temperature 55℃ until the D50 particle size of the precursor reaches 10μm. Separate the solid and liquid, and obtain precursor particles with hierarchical structure after washing, filtering, drying and crushing and sieving the solid product.
[0130] (4) Precursor pre-calcination: Precursor particles and LiOH powder were weighed according to the ratio of Li molar amount to total molar amount of metal elements in the precursor = 1.08, and 5 wt% of barium titanate was weighed in the precursor particles. The mixture was thoroughly mixed and pre-calcined at 550℃ for 6 hours in a pure oxygen atmosphere at a heating rate of 2℃ / min. After the pre-calcination was completed, the precursor pre-calcined material was obtained by crushing and sieving.
[0131] (5) Preparation of cathode material: The precursor pre-calcined material was sintered at 850℃ for 15h in a pure oxygen atmosphere, with a heating rate of 2℃ / min. After the sintering was completed, the high-nickel polycrystalline cathode material was obtained by crushing and sieving.
[0132] Example 8
[0133] This application is basically the same as Example 1, except that in this example, the barium titanate dispersion in step (3) is replaced with lead zirconate titanate dispersion (the solid-liquid mass ratio of lead zirconate titanate dispersion is 1:50), and the barium titanate in step (4) is replaced with lead zirconate titanate.
[0134] Comparative Example 1
[0135] This comparative example provides a method for preparing a cathode material, including the following steps:
[0136] (1) Solution preparation: Mix NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O, MgSO4·7H2O, TiOSO4, and (NH4)6Mo7O. 24 Prepare a 2 mol / L metal salt solution of Nb(HC2O4)5 according to the molar ratio of Ni:Co:Mn:Mg:Ti:Mo:Nb=88:3:3:2:2:1:1; prepare a 10 mol / L NaOH solution and a 12.5 mol / L ammonia solution for later use; add NaOH and ammonia to pure water to control its pH to 12 and ammonia value to 5 g / L, and record this as base solution 1; add NaOH and ammonia to pure water to control its pH to 11 and ammonia value to 5 g / L, and record this as base solution 2.
[0137] (2) Preparation of precursor crystal nuclei: Add 2L of bottom liquid 1 to the reaction vessel, introduce nitrogen gas, and introduce the prepared metal salt solution, NaOH solution and ammonia solution into the reaction vessel at a speed of 1000rpm. The flow rate of the metal salt solution is 0.6L / h and the flow rate of the ammonia solution is 0.05L / h. React at pH 11 and temperature of 55℃ until the D50 particle size of the precursor reaches 3μm. Separate the solid and liquid, and obtain the precursor crystal nuclei by washing, filtering, drying and crushing the solid product.
[0138] (3) Precursor growth: Add the precursor nuclei prepared in step (2) and 2L of bottom liquid 2 to the reactor, introduce nitrogen gas, and introduce the prepared metal salt solution, NaOH solution and ammonia solution into the reactor at a speed of 1000rpm. The flow rate of the metal salt solution is 0.6L / h and the flow rate of the ammonia solution is 0.05L / h. React at pH 11 and temperature of 55℃ until the D50 particle size of the precursor reaches 10μm. Separate the solid and liquid, and obtain the precursor particles with hierarchical structure after washing, filtering, drying and crushing and sieving the solid product.
[0139] (4) Precursor pre-calcination: Precursor particles and LiOH powder were weighed according to the ratio of Li molar amount to total molar amount of metal elements in the precursor = 1.08, and thoroughly mixed. The mixture was pre-calcined at 550℃ for 6 hours under a pure oxygen atmosphere with a heating rate of 2℃ / min. After the pre-calcination was completed, the precursor pre-calcined material was obtained by crushing and sieving.
[0140] (5) Preparation of cathode material: The precursor pre-calcined material was sintered at 850℃ for 15h in a pure oxygen atmosphere, with a heating rate of 2℃ / min. After the sintering was completed, the high-nickel polycrystalline cathode material was obtained by crushing and sieving.
[0141] Comparative Example 2
[0142] This comparative example provides a method for preparing a cathode material, including the following steps:
[0143] (1) Solution preparation: Mix NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O, MgSO4·7H2O, TiOSO4, and (NH4)6Mo7O. 24 Prepare a 2 mol / L metal salt solution of Nb(HC2O4)5 according to the molar ratio of Ni:Co:Mn:Mg:Ti:Mo:Nb=88:3:3:2:2:1:1; prepare a 10 mol / L NaOH solution and a 12.5 mol / L ammonia solution for later use; add NaOH and ammonia to pure water to control its pH to 12 and ammonia value to 5 g / L, and record this as base solution 1; add NaOH and ammonia to pure water to control its pH to 11 and ammonia value to 5 g / L, and record this as base solution 2.
[0144] (2) Preparation of precursor crystal nuclei: Add 2L of bottom liquid 1 to the reaction vessel, introduce nitrogen gas, and introduce the prepared metal salt solution, NaOH solution and ammonia solution into the reaction vessel at a speed of 1000rpm. The flow rate of the metal salt solution is 0.6L / h and the flow rate of the ammonia solution is 0.05L / h. React at pH 11 and temperature of 55℃ until the D50 particle size of the precursor reaches 3μm. Separate the solid and liquid, and obtain the precursor crystal nuclei by washing, filtering, drying and crushing the solid product.
[0145] (3) Precursor growth: Add the precursor nuclei prepared in step (2) and 2L of bottom liquid 2 to the reactor, introduce nitrogen gas, and introduce the prepared metal salt solution, NaOH solution and ammonia solution into the reactor at a speed of 1000rpm. The flow rate of the metal salt solution is 0.6L / h and the flow rate of the ammonia solution is 0.05L / h. React at pH 11 and temperature of 55℃ until the D50 particle size of the precursor reaches 10μm. Separate the solid and liquid, and obtain the precursor particles with hierarchical structure after washing, filtering, drying and crushing and sieving the solid product.
[0146] (4) Precursor pre-calcination: Precursor particles and LiOH powder were weighed according to the ratio of Li molar amount to total molar amount of metal elements in the precursor = 1.08, and 1 wt% of barium titanate was weighed in the precursor particles. They were thoroughly mixed and pre-calcined at 550℃ for 6 hours in a pure oxygen atmosphere at a heating rate of 2℃ / min. After the pre-calcination was completed, the precursor pre-calcined material was obtained after crushing and sieving.
[0147] (5) Preparation of cathode material: The precursor pre-calcined material was sintered at 850℃ for 15h in a pure oxygen atmosphere, with a heating rate of 2℃ / min. After the sintering was completed, the high-nickel polycrystalline cathode material was obtained by crushing and sieving.
[0148] Comparative Example 3
[0149] This comparative example provides a method for preparing a cathode material, including the following steps:
[0150] (1) Solution preparation: Mix NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O, MgSO4·7H2O, TiOSO4, and (NH4)6Mo7O. 24 Prepare a 2 mol / L metal salt solution of Nb(HC2O4)5 according to the molar ratio of Ni:Co:Mn:Mg:Ti:Mo:Nb=88:3:3:2:2:1:1; prepare a 10 mol / L NaOH solution and a 12.5 mol / L ammonia solution for later use; add NaOH and ammonia to pure water to control its pH to 12 and ammonia value to 5 g / L, and record this as base solution 1; add NaOH and ammonia to pure water to control its pH to 11 and ammonia value to 5 g / L, and record this as base solution 2.
[0151] (2) Preparation of precursor crystal nuclei: Add 2L of bottom liquid 1 to the reaction vessel, introduce nitrogen gas, and introduce the prepared metal salt solution, NaOH solution and ammonia solution into the reaction vessel at a speed of 1000rpm. The flow rate of the metal salt solution is 0.6L / h and the flow rate of the ammonia solution is 0.05L / h. React at pH 11 and temperature of 55℃ until the D50 particle size of the precursor reaches 3μm. Separate the solid and liquid, and obtain the precursor crystal nuclei by washing, filtering, drying and crushing the solid product.
[0152] (3) Precursor growth: Add the precursor nuclei prepared in step (2) and 2L of bottom liquid 2 to the reactor, introduce nitrogen gas, and introduce the prepared metal salt solution, NaOH solution, ammonia solution and barium titanate dispersion (the solid-liquid mass ratio of barium titanate dispersion is 1:50) into the reactor at a speed of 1000 rpm. The flow rate ratio of metal salt solution to barium titanate dispersion is 10:1, the flow rate of metal salt solution is 0.6L / h, and the flow rate of ammonia solution is 0.05L / h. React under the conditions of pH 11 and temperature 55℃ until the D50 particle size of the precursor reaches 10μm. Separate the solid and liquid, and obtain precursor particles with hierarchical structure after washing, filtering, drying and crushing and sieving the solid product.
[0153] (4) Precursor pre-calcination: Precursor particles and LiOH powder were weighed according to the ratio of Li molar amount to total molar amount of metal elements in the precursor = 1.08, and thoroughly mixed. The mixture was pre-calcined at 550℃ for 6 hours under a pure oxygen atmosphere with a heating rate of 2℃ / min. After the pre-calcination was completed, the precursor pre-calcined material was obtained by crushing and sieving.
[0154] (5) Preparation of cathode material: The precursor pre-calcined material was sintered at 850℃ for 15h in a pure oxygen atmosphere, with a heating rate of 2℃ / min. After the sintering was completed, the high-nickel polycrystalline cathode material was obtained by crushing and sieving.
[0155] The high-nickel polycrystalline cathode materials prepared in each embodiment and comparative example were used to prepare cathode sheets and assembled into batteries for electrochemical performance testing.
[0156] Test method:
[0157] 4C rate capacity retention: The prepared battery was tested on a NEWARE battery charge / discharge tester at 25℃. It was charged at 1C constant current to 4.3V, then allowed to rest for 1 minute, and discharged at 0.2C constant current to 3.0V, followed by a 1-minute rest. This process was repeated 5 times. Then, the lithium-ion battery was charged at 1C constant current to 4.3V, allowed to rest for 1 minute, and discharged at 0.5C constant current to 3.0V, followed by a 1-minute rest. This process was repeated 5 times. Finally, the lithium-ion battery was charged at 1C constant current to 4.3V, allowed to rest for 1 minute, and discharged at 1C constant current to 3.0V, followed by a 1-minute rest. This process was repeated 5 times. The 4C rate capacity retention rate = (Discharge capacity of the last 4C discharge cycle / Discharge capacity of the first 0.2C cycle) × 100%.
[0158] Battery capacity retention test after 200 cycles: The prepared battery was tested on a NEWARE battery charge-discharge tester at a temperature of 25℃. It was charged to 4.3V at a constant current of 1C, then left to stand for 1 minute, and discharged to 3.0V at a constant current of 1C, and then left to stand for 1 minute. The cycle capacity retention rate was calculated as (discharge capacity of the last cycle / discharge capacity of the first cycle) × 100%.
[0159] The test results are shown in Table 1.
[0160] Table 1 Battery Performance
[0161]
[0162]
[0163] As shown in Table 1, the cathode material of this application significantly improves the rate performance and cycle performance of the battery.
[0164] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A positive electrode material, characterized in that, It includes polycrystalline ternary cathode active material particles and a coating layer disposed on the surface of the polycrystalline ternary cathode active material particles; the polycrystalline ternary cathode active material particles include a core and a buffer layer from the inside out; The core includes ternary positive electrode active material particles A; The buffer layer comprises ternary positive electrode active material particles B and dielectric piezoelectric material A; the dielectric constant ε of the dielectric piezoelectric material A is greater than 1000, and the piezoelectric constant d is greater than 100 pC / N; The coating layer includes a dielectric piezoelectric material B.
2. The cathode material according to claim 1, characterized in that, At least one of the following conditions must be met: (1) The D50 particle size of the secondary particles of the polycrystalline ternary positive electrode active material particles is 5-15 μm, and can be selected as 10-12 μm; (2) The chemical formula of the ternary positive electrode active material particle A is LiNi x1 Co y1 Mn z1 M 1-x1-y1-z1 O2, where 0.8≤x1≤0.95, x1+y1+z1≤1, and M includes one or more of Al, Mg, Ti, W, Fe, Mo, Zr, Nb, Zn, La, Ca, Sr, Sn, Sb, Si, Ba, Y, Ta and Ce; Optionally, 0.85≤x1≤0.9, M includes Mg, Ti, Nb, and Mo; (3) The D50 particle size of the core is 1 to 4 μm, and can be selected as 2.5 to 3.5 μm.
3. The cathode material according to claim 2, characterized in that, At least one of the following conditions must be met: (1) The thickness of the buffer layer is 4 to 15 μm, and can be 8 to 10 μm; (2) The dielectric piezoelectric material A includes one or more of barium titanate, bismuth titanate, lanthanum titanate, lead zirconate titanate, or lead magnesium niobium zirconate titanate. (3) The chemical formula of the ternary positive electrode active material particle B is LiNi x2 Co y2 Mn z2 K 1-x2-y2-z2 O2, where 0.8≤x2≤0.95, x2+y2+z2≤1, and K includes one or more of Al, Mg, Ti, W, Fe, Mo, Zr, Nb, Zn, La, Ca, Sr, Sn, Sb, Si, Ba, Y, Ta and Ce; Optionally, 0.85 ≤ x2 ≤ 0.9, and K includes Mg, Ti, Nb, and Mo; (4) The chemical formula of the ternary positive electrode active material particle A is the same as or different from that of the ternary positive electrode active material particle B.
4. The cathode material according to claim 1, characterized in that, At least one of the following conditions must be met: (1) The dielectric piezoelectric material B includes one or more of barium titanate, bismuth titanate, lanthanum titanate, lead zirconate titanate, or lead magnesium niobium zirconate titanate. (3) The mass of the coating layer is 0.5wt% to 5wt% of the total mass of the core and buffer layer, and can be selected as 1wt% to 1.5wt%. (4) The dielectric constant ε of the dielectric piezoelectric material B is greater than 1000, and the piezoelectric constant d is greater than 100pC / N; (5) The dielectric volt-electric material B is the same as or different from the dielectric volt-electric material A.
5. A method for preparing the cathode material according to any one of claims 1-4, characterized in that, The following steps are involved: S1. Preparation of precursor crystal nuclei; S2. The precursor crystal nuclei are fed into a coprecipitation reactor. A second metal salt solution, a second alkaline solution, a second complex solution, and a dispersion of dielectric and electrostatic material A are added to the coprecipitation reactor. The pH2 and temperature T2 are controlled to react and obtain the precursor. S3. The precursor is mixed with a lithium source and dielectric piezoelectric material B, and then subjected to a first sintering to obtain a precursor pre-sintered material. S4. The precursor pre-burned material is subjected to a second sintering to obtain the cathode material.
6. The method for preparing the cathode material according to claim 5, characterized in that, S1 includes: adding a first metal salt solution, a first alkaline solution and a first complex solution into a coprecipitation reactor, controlling pH1 and temperature T1, and reacting in the reactor to obtain the precursor crystal nucleus; Optionally, the pH1 is 10 to 12; Optionally, T1 is 45–60°C; Optionally, the D50 particle size of the precursor nucleus is 1–4 μm, and can be 2.5–3.5 μm; Optionally, in step S1, the stirring speed is controlled to be 500–1500 rpm during the reaction process; Optionally, the first metal salt in the first metal salt solution includes one or more of the following: sulfate, acetate, nitrate, oxalate, and chloride salt corresponding to each metal. Optionally, the first alkaline solution includes one or more of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution, or ammonium carbonate solution; Optionally, the first complex solution includes one or more of ammonia, oxalic acid solution, or citric acid solution; Optionally, the total molar concentration of the metal element in the first metal salt solution is 1–5 mol / L; Optionally, the concentration of the first alkaline solution is 5–12 mol / L, and optionally 8–10 mol / L; Optionally, the concentration of the first complex solution is 5–15 mol / L, and optionally 10–13 mol / L.
7. The method for preparing the cathode material according to claim 5 or 6, characterized in that, S2 satisfies at least one of the following conditions: (1) The pH2 is 10-12; (2) The T2 is 45-60℃; (3) In S2, during the reaction process, the stirring speed is controlled to be 600-1500 rpm; (4) The second metal salt in the second metal salt solution includes one or more of the sulfate, acetate, nitrate, oxalate, and chloride salts corresponding to each metal; (5) The second alkaline solution includes one or more of sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution or ammonium carbonate solution; (6) The second complex solution includes one or more of ammonia, oxalic acid solution or citric acid solution; (7) The total molar concentration of metal elements in the second metal salt solution is 1 to 5 mol / L; (8) The concentration of the second alkaline solution is 5-12 mol / L, and can be selected as 8-10 mol / L; (9) The concentration of the second complex solution is 5-15 mol / L, and can be selected as 10-13 mol / L; (10) The solid-liquid mass ratio of the dielectric electroelectric material A dispersion is 1:20 to 1:100; (11) The flow rate ratio of the metal salt solution to the dispersion of dielectric electrostatic material A is (3-20):
1.
8. The method for preparing the cathode material according to claim 5 or 6, characterized in that, At least one of the following conditions must be met: (1) In S3, the lithium source includes one or more of lithium hydroxide and lithium carbonate; (2) In S3, the ratio of the molar amount of Li element in the lithium source to the total molar amount of metal element in the precursor is 1.00 to 1.15, and can be selected as 1.03 to 1.08; (3) In S3, the temperature of the first sintering is 450-650℃, which can be selected as 500-600℃; the sintering time is 5-10h. (4) In S3, the heating rate of the first sintering is 1 to 10 °C / min, and can be selected as 2 to 5 °C / min; (5) In S3, the atmosphere of the first sintering is air or pure oxygen atmosphere; (6) In S4, the temperature of the second sintering is 750-950℃, and can be selected as 800-850℃; the sintering time is 10-24h; (7) In S4, the heating rate of the second sintering is 1 to 10 °C / min, and can be selected as 2 to 5 °C / min; (8) In S3, the atmosphere for the second sintering is a pure oxygen atmosphere.
9. A positive electrode sheet, characterized in that, This includes the cathode material according to any one of claims 1-4 or the cathode material prepared by the preparation method according to any one of claims 5-8.
10. A lithium-ion secondary battery, characterized in that, Includes the positive electrode sheet as described in claim 9.