Composite-doped high-nickel large single-crystal ternary layered oxide positive electrode material and preparation method and application thereof

Abstract

The application provides a kind of composite doped high-nickel large single-crystal ternary layered oxide positive electrode material, comprising: substrate;Coating layer arranged on the surface of the substrate;The lithium nickel cobalt manganese oxide containing bulk phase flux and lattice stabilizer in the substrate;The coating layer contains surface dopant.The method provided by the application only carries out sintering once to form a larger single crystal, compared with conventional sintering cost and crushing cost is reduced, without water washing pollution;The synergistic effect caused by multiple dopants makes the particle grow and the crystal inside and surface stable, the capacity and rate are improved in solid-state battery.

Description

Technical Field

[0001] This invention relates to the field of cathode material technology, and particularly to a composite-doped high-nickel large single-crystal ternary layered oxide cathode material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries with traditional organic liquid electrolytes suffer from energy density bottlenecks and safety risks such as flammability, explosion, and solvent leakage. All-solid-state batteries can ultimately solve these safety issues and improve energy density by replacing liquid electrolytes with solid electrolytes. To achieve high-energy-density all-solid-state batteries, nickel-rich layered oxides, especially single-crystal types, are of great significance for practical applications and commercialization due to their high energy density and structural stability.

[0003] Patent CN114725371A discloses a high-nickel single-crystal cathode material and its preparation method, as well as lithium-ion batteries and all-solid-state batteries. It employs a stepwise solid-state calcination method to achieve in-situ coating, utilizing a single calcination to achieve rapid and uniform core growth, and a second calcination to replenish lithium and compensate for oxygen defects introduced by the first high-temperature calcination, achieving high compatibility with solid-state electrolytes and improving cycle stability in all-solid-state batteries. However, due to the need for multiple mixing and sintering processes, it places high demands on equipment and costs. Patent CN114094080A discloses a single-crystal lithium-rich layered-spinel composite cathode material and its preparation method. It uses a two-stage lithium-addition sintering method to prepare single-crystal high-nickel cathode materials, reducing the interfacial impedance between the cathode material and the solid electrolyte, minimizing side reactions, and improving the electrochemical performance and cycle life of the cathode sheet. However, the lithium-rich material used in this method has an unstable structure and is prone to lithium plating, making mass production difficult. Patent CN112635752A discloses a ternary cathode material, its preparation method, and a lithium battery. A single-phase rock salt ternary precursor is prepared by ball milling NiO, MnO, and Co3O4 powders, followed by high-temperature calcination in a mixed molten salt to obtain ultra-large single crystals. This method can improve cycle performance in all-solid-state batteries. However, the precursor composition is uneven and prone to decomposition; furthermore, the molten salt is difficult to remove, causing significant environmental pollution. Patent CN112164776A discloses a composite-coated all-solid-state battery cathode material, its preparation method, and an all-solid-state battery. This method uses lithium-containing metal oxides and conductive materials to coat the cathode material to prepare a composite cathode material. Its application in all-solid-state batteries can improve rate performance and cycle performance. However, this method mainly modifies the surface and fails to optimize the cathode material itself, thus failing to overcome the problem of structural stability.

[0004] The contact between single-crystal ternary cathode materials and solid electrolytes presents challenges, exhibiting high surface impedance and interfacial instability. Current methods primarily focus on coating to mitigate side reactions between the cathode and solid electrolyte through multiple calcinations to repair oxygen defects and coating with metal oxides. This aims to reduce interfacial impedance, achieve suitable capacity utilization, and ensure stable cycling. However, these technologies are limited by their cumbersome processes, requiring multiple sintering operations that are energy-intensive, and the associated environmental pollution. Furthermore, the small size of the single-crystal particles hinders lithium-ion transport in the solid-solid interface, preventing the formation of a suitable ion network. Simply increasing the sintering temperature to raise the single-crystal grain size leads to a severe increase in lithium-nickel mixing (exceeding 5%), disrupting the layered structure and resulting in extremely poor material capacity utilization. Therefore, developing a single-crystal material with a stable crystal structure, low lithium-nickel mixing, stable contact with the solid electrolyte, and a larger grain size, achieved through a single sintering process, is crucial. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a composite-doped high-nickel large single-crystal ternary layered oxide cathode material, its preparation method and application. The method provided by the present invention obtains a single crystal with stable crystal structure, stable interface contact and large grain size in a single sintering process, which can be applied to solid-state batteries.

[0006] This invention provides a composite-doped high-nickel large single-crystal ternary layered oxide cathode material, comprising:

[0007] The substrate contains a bulk flux, a lattice stabilizer, and lithium nickel cobalt manganese oxide;

[0008] A coating layer disposed on the surface of the substrate, the coating layer containing a surface dopant.

[0009] Preferably, the bulk flux is selected from one or more of strontium oxide, strontium carbonate, strontium nitrate and strontium hydroxide; the mass of the bulk flux is 500 to 10000 ppm of the mass of lithium nickel cobalt manganese oxide.

[0010] Preferably, the lattice stabilizer is selected from one or more of metal oxides, hydroxides, and chlorides; the metal is selected from one or more of zirconium, titanium, tungsten, and yttrium; and the mass of the lattice stabilizer is 500 to 10,000 ppm of lithium nickel cobalt manganese oxide.

[0011] Preferably, the surface dopant is selected from boron-containing materials; the mass of the surface dopant is 500 to 10000 ppm of lithium nickel cobalt manganese oxide.

[0012] Preferably, the chemical formula of the composite-doped high-nickel large single-crystal ternary layered oxide cathode material is shown in Formula I:

[0013] Li a Nix Co y Mn z A α B β C γ O2 type I;

[0014] In Equation I, 0.98 ≤ a ≤ 1.05, 0.80 ≤ x ≤ 0.98, 0.05 ≤ y ≤ 0.15, z = 1 - xy.

[0015] 0.0005≤α≤0.01, 0.0005≤β≤0.01, 0.0005≤γ≤0.01;

[0016] A is selected from metallic elements in bulk fluxes;

[0017] B is selected from metallic elements in lattice stabilizers;

[0018] C is selected from surface dopant elements.

[0019] Preferably, the composite-doped high-nickel large single-crystal ternary layered oxide cathode material has a D50 of 4–10 μm, a particle diameter of 1.5–25 μm, and a SPAN of 0.8–1.5.

[0020] The specific surface area of ​​the composite-doped high-nickel large single-crystal ternary layered oxide cathode material is 0.2–0.4 cm². 2 / g; compacted density is 3.2~3.5g / cm³ 3 ;

[0021] The I obtained by XRD detection of the composite-doped high-nickel large single-crystal ternary layered oxide cathode material 003 / I 104 The value is 1.5–2.5, and the c / a value is 4.93–4.94. (FWHM) (003) The concentration is 0.06–0.12, and the lithium-nickel mixing rate is 1–3%.

[0022] The composite-doped high-nickel large single-crystal ternary layered oxide cathode material contains Li₂CO₃ with a mass content ≤3000ppm, LiOH with a mass content ≤5000ppm, and Free Li + The mass content is ≤2000ppm.

[0023] This invention provides a method for preparing the composite-doped high-nickel large single-crystal ternary layered oxide cathode material described in the above-mentioned technical solution, comprising:

[0024] The additives, lithium salts, and lithium nickel cobalt manganese oxide precursor were mixed to obtain a mixture;

[0025] The mixture was subjected to low-temperature sintering, high-temperature sintering and medium-temperature sintering in sequence to obtain the sintered product;

[0026] The sintered product is not washed with water to obtain a composite-doped high-nickel large single crystal ternary layered oxide cathode material.

[0027] The additives include:

[0028] Bulk flux, lattice stabilizer and surface dopant.

[0029] Preferably, the low-temperature sintering temperature is 450–600℃ and the low-temperature sintering time is 2–4 hours; the high-temperature sintering temperature is 850–950℃ and the high-temperature sintering time is 5–10 hours; the medium-temperature sintering temperature is 700–800℃ and the medium-temperature sintering time is 5–10 hours.

[0030] The present invention provides a composite cathode, comprising: the composite-doped high-nickel large single-crystal ternary layered oxide cathode material and the electrolyte described in the above technical solution.

[0031] This invention provides a solid-state battery, comprising: the composite-doped high-nickel large single-crystal ternary layered oxide cathode material described in the above technical solution.

[0032] The method provided by this invention forms a larger single crystal through a single sintering process, which reduces sintering and crushing costs compared to conventional methods and eliminates water washing pollution. The synergistic effect caused by multiple dopants enables the particles to grow and stabilize the internal and surface of the crystal, thus improving both capacity and rate capability in solid-state batteries. Attached Figure Description

[0033] Figure 1 The image shown is a SEM-EDS image of the single-crystal cathode material prepared in Example 1 of this invention.

[0034] Figure 2 The image shows the XRD pattern of the single-crystal cathode material prepared in Example 1 of this invention.

[0035] Figure 3 This is a SEM image of the single-crystal cathode material prepared in Example 1 of the present invention;

[0036] Figure 4 This is a SEM image of the single-crystal cathode material prepared in Comparative Example 1 of this invention;

[0037] Figure 5 This is a SEM image of the single-crystal cathode material prepared in Comparative Example 2 of this invention;

[0038] Figure 6 Here is a SEM image of the single-crystal cathode material prepared in Comparative Example 3 of this invention;

[0039] Figure 7 This is a SEM image of the single-crystal cathode material prepared in Comparative Example 4 of this invention;

[0040] Figure 8 This is a SEM image of the single-crystal cathode material prepared in Comparative Example 5 of this invention;

[0041] Figure 9 This is a SEM image of the single-crystal cathode material prepared in Comparative Example 6 of this invention;

[0042] Figure 10 This is a SEM image of the single-crystal cathode material prepared in Comparative Example 7 of this invention. Detailed Implementation

[0043] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] This invention provides a composite-doped high-nickel large single-crystal ternary layered oxide cathode material, comprising:

[0045] Substrate;

[0046] A coating layer disposed on the surface of the substrate.

[0047] In this invention, the substrate contains a bulk flux, a lattice stabilizer, and lithium nickel cobalt manganese oxide; the coating layer contains a surface dopant.

[0048] In this invention, the bulk flux is preferably selected from one or more of strontium oxide, strontium carbonate, strontium nitrate and strontium hydroxide; the mass of the bulk flux is preferably 500-10000 ppm of lithium nickel cobalt manganese oxide, more preferably 1000-8000 ppm, even more preferably 3000-6000 ppm, and most preferably 4000-5000 ppm.

[0049] In this invention, the lattice stabilizer is preferably selected from one or more of metal oxides, hydroxides, and chlorides; the metal is preferably selected from one or more of zirconium, titanium, tungsten, and yttrium; the mass of the lattice stabilizer is preferably 500-10000 ppm of lithium nickel cobalt manganese oxide, more preferably 1000-8000 ppm, even more preferably 3000-6000 ppm, and most preferably 4000-5000 ppm.

[0050] In this invention, the surface dopant is preferably selected from boron-containing substances, more preferably from one or more of boron oxide, boric acid, and lithium borate; the mass of the surface dopant is preferably 500-10000 ppm of the mass of lithium nickel cobalt manganese oxide, more preferably 1000-8000 ppm, more preferably 3000-6000 ppm, and most preferably 4000-5000 ppm.

[0051] In this invention, strontium doping acts as a flux, increasing the single crystal size, improving the contact between the cathode material and the solid electrolyte, and increasing the utilization rate of the cathode material, thereby improving the overall energy density of the solid-state battery; the presence of high-valence ions in lattice stabilizers such as zirconium increases the Li... + The energy barrier of octahedral-tetrahedral-octahedral interstitial (oto) transitions increases the strength of single-crystal particles, improving the pressure tolerance and cycle stability of solid-state batteries. Surface doping of boron reduces the surface energy of the (003) crystal face, maximizing the preferred growth of the (003) face and forming fast-ion conductors such as lithium metaborate and lithium pyroborate, isolating the solid electrolyte from side reactions with the high-nickel surface, thereby improving the rate performance of solid-state batteries and reducing surface side reactions. Furthermore, through the synergistic effect of different dopants—the flux melting outside the single crystal to provide lower reaction energy—the lattice stabilizer enters the single crystal with less resistance, resulting in more uniform doping and increased interlayer spacing, facilitating lithium-ion insertion and extraction. Simultaneously, the surface dopants, due to the internal stability of the crystal and the uniform external surface energy, form a stable coating layer on the single crystal surface, with a small amount of boron doping near the surface. Under the synergistic effect of these three additives, single-crystal particles with large particle size, stable overall structure, and uniform surface distribution can be obtained, suitable for use in sulfide all-solid-state batteries.

[0052] In this invention, strontium is used as a flux in nickel-cobalt-manganese to increase the grain size to over 3 μm. High-valence elements such as zirconium, titanium, tungsten, and yttrium are doped into the lattice to improve the particle strength. Then, boron is used for surface doping to reduce the surface energy of the (003) crystal plane, resulting in the maximization of the preferred growth of the (003) plane and the formation of fast ion conductors such as lithium metaborate and lithium pyroborate, which improves the contact side reactions of solid-state batteries. Through the synergistic effect of composite doping, the material has the characteristics of low lithium-nickel mixing and stable layered structure.

[0053] In this invention, the preferred chemical formula of the composite-doped high-nickel large single-crystal ternary layered oxide cathode material is as shown in Formula I:

[0054] Li a Ni x Co y Mn z A α B β C γ O2 type I;

[0055] In Equation I, 0.98 ≤ a ≤ 1.05, 0.80 ≤ x ≤ 0.98, 0.05 ≤ y ≤ 0.15, z = 1 - xy.

[0056] 0.0005≤α≤0.01, 0.0005≤β≤0.01, 0.0005≤γ≤0.01;

[0057] A is selected from metallic elements in bulk fluxes, such as strontium; B is selected from metallic elements in lattice stabilizers, such as one or more of zirconium, titanium, tungsten, and yttrium; and C is selected from surface dopant elements, such as boron.

[0058] In this invention, α is preferably 0.99–1.04, more preferably 0.99–1.02, and most preferably 1.00–1.01; x is preferably 0.85–0.95, more preferably 0.88–0.92, and most preferably 0.90; y is preferably 0.08–0.12, more preferably 0.1; and α is preferably 0.001–0.009, more preferably 0.002–0.008, more preferably 0.003–0.007, and even more preferably 0.0 The β is preferably 0.001 to 0.009, more preferably 0.002 to 0.008, more preferably 0.003 to 0.007, more preferably 0.004 to 0.006, and most preferably 0.005; the γ is preferably 0.001 to 0.009, more preferably 0.002 to 0.008, more preferably 0.003 to 0.007, more preferably 0.004 to 0.006, and most preferably 0.005.

[0059] In this invention, the median particle size D50 of the composite-doped high-nickel large single-crystal ternary layered oxide cathode material is preferably 4-10 μm, more preferably 6-8 μm; the particle diameter is preferably 1.5 μm ≤ D ≤ 25 μm, more preferably 1.8 μm ≤ D ≤ 20 μm; SPAN = (D90-D10) / D50 is preferably 0.8-1.5, more preferably 1-1.2; and the average particle size is preferably 3-4 μm, more preferably 3.5 μm.

[0060] In this invention, the specific surface area of ​​the composite-doped high-nickel large single-crystal ternary layered oxide cathode material is preferably 0.2–0.4 cm². 2 / g, more preferably 0.3-0.35cm 2 / g; the preferred compaction density is 3.2–3.5 g / cm³. 3 More preferably, it is 3.3–3.4 g / cm³. 3 .

[0061] In this invention, the intensity ratio of the 003 peak to the 104 peak obtained by XRD detection of the composite-doped high-nickel large single-crystal ternary layered oxide cathode material is I. 003 / I 104 The preferred value is 1.5 to 2.5, more preferably 1.8 to 2.2; the c / a ratio of the c-axis length to the a-axis length in the layered structure is preferably 4.93 to 4.94, more preferably 4.932 to 4.936; the half-maximum width at half maximum (FWHM) of the 003 crystal plane is preferably 0.06 to 0.12, more preferably 0.08 to 0.1, and most preferably 0.09; the lithium-nickel mixing ratio (the percentage of lithium sites occupied by nickel in the layered structure) is preferably 1 to 3%, more preferably 1.5 to 2.5%, and most preferably 2%.

[0062] In this invention, the mass content of Li2CO3 in the composite-doped high-nickel large single-crystal ternary layered oxide cathode material is preferably ≤3000ppm, more preferably ≤2000ppm; the mass content of LiOH is preferably ≤5000ppm, more preferably ≤3000ppm; Free Li + The mass content is preferably ≤2000ppm, more preferably ≤1500ppm.

[0063] In this invention, the impedance of the composite-doped high-nickel large single crystal ternary layered oxide cathode material at 3.5 MPa is preferably 500 to 1500 ohm-cm, more preferably 600 to 1200 ohm-cm.

[0064] This invention provides a method for preparing the composite-doped high-nickel large single-crystal ternary layered oxide cathode material described in the above-mentioned technical solution, comprising:

[0065] The additives, lithium salts, and lithium nickel cobalt manganese oxide precursor were mixed to obtain a mixture;

[0066] The mixture was subjected to low-temperature sintering, high-temperature sintering and medium-temperature sintering in sequence to obtain the sintered product;

[0067] Without washing the sintered product with water, a composite-doped high-nickel large single-crystal ternary layered oxide cathode material is obtained.

[0068] The preparation method provided by this invention involves only one sintering process and requires no water washing.

[0069] In this invention, the additive includes:

[0070] Bulk flux, lattice stabilizer and surface dopant.

[0071] In this invention, the composition of the bulk flux, lattice stabilizer and surface dopant is consistent with that described in the above technical solution, and will not be repeated here.

[0072] In this invention, the lithium salt is preferably selected from one or more of lithium hydroxide, lithium nitrate, lithium carbonate, and lithium oxide.

[0073] In this invention, the preferred composition of the nickel-cobalt-manganese-lithium precursor is:

[0074] Ni x Co y Mn z (OH)2 Formula II;

[0075] In Equation II, 0.80≤x≤0.98, 0.05≤y≤0.15, z=1-xy.

[0076] In this invention, the ratio of the additive to the nickel cobalt manganese lithium precursor is sufficient to satisfy the mass ratio of the additive to the nickel cobalt manganese lithium oxide in the substrate and the coating layer in the above technical solution.

[0077] In this invention, the molar ratio of metal elements in the lithium salt and the nickel-cobalt-manganese-lithium precursor is preferably (0.98-1.05):1, more preferably (0.99-1.04):1, even more preferably (1.00-1.03):1, and most preferably (1.01-1.02):1.

[0078] In this invention, the mixing is preferably carried out under stirring conditions; the stirring speed is preferably 600-1000 r / min, more preferably 700-900 r / min, and most preferably 800 r / min; the mixing time is preferably 10-20 min, more preferably 13-17 min, and most preferably 15 min.

[0079] In this invention, the temperature of the low-temperature sintering is preferably 450–600°C, more preferably 500–550°C, and most preferably 520–530°C; the time of the low-temperature sintering is preferably 2–4 hours, more preferably 2.5–3.5 hours, and most preferably 3 hours; the temperature of the high-temperature sintering is preferably 850–950°C, more preferably 880–920°C, and most preferably 920°C; the time of the high-temperature sintering is preferably 5–10 hours, more preferably 6–9 hours, and most preferably 7–8 hours; the temperature of the medium-temperature sintering is preferably 700–800°C, more preferably 720–780°C, more preferably 740–760°C, and most preferably 750°C; the time of the medium-temperature sintering is preferably 5–10 hours, more preferably 6–9 hours, and most preferably 7–8 hours.

[0080] In this invention, the heating rate and cooling rate during the low-temperature sintering, high-temperature sintering and medium-temperature sintering processes are preferably independently selected from 2 to 5 °C / min, more preferably 3 to 4 °C / min; the sintering atmosphere is preferably oxygen.

[0081] In this invention, low-temperature sintering allows lithium salts to flow fully, promoting uniform material properties; high-temperature sintering enables lithium intercalation and crystal growth, while the insertion of dopants achieves lattice and surface stability of single-crystal particles; and medium-temperature sintering can repair oxygen defects that occur during high-temperature processes, improving the capacity and rate performance of the material.

[0082] In this invention, the conventional multiple sintering processes are integrated into a single sintering process, meaning the product is obtained after only one mixing and sintering. This reduces energy consumption and process complexity, lowering sintering costs by 30%. Simultaneously, the larger single-crystal particles have lower surface energy and better dispersibility, reducing crushing costs by 40%. Subsequent processing eliminates the need for water washing, reducing environmental pollution risks. If surface dopants are not added during the first sintering stage, but instead added during the second or even third sintering stage, although a coating layer may form on the surface, the lack of a bulk flux to reduce surface energy prevents near-surface doping to lower interfacial impedance, resulting in relatively poor electrochemical performance.

[0083] In this invention, the process of obtaining the sintered product preferably further includes:

[0084] The sintered product was crushed and sieved to obtain a composite-doped high-nickel large single crystal ternary layered oxide cathode material.

[0085] In this invention, the pulverization is preferably airflow pulverization.

[0086] The present invention provides a composite cathode, comprising: the composite-doped high-nickel large single-crystal ternary layered oxide cathode material described in the above technical solution.

[0087] In this invention, the composite electrode preferably further includes an electrolyte.

[0088] In this invention, the electrolyte is preferably a sulfide electrolyte, and more preferably a Li6PS5Cl solid electrolyte.

[0089] In this invention, the mass ratio of the composite-doped high-nickel large single-crystal ternary layered oxide cathode material to the electrolyte is preferably (1-6):1, more preferably (3-5):1, and most preferably 4:1.

[0090] In this invention, the impedance of the composite positive electrode is preferably 10–50 Ω, more preferably 20–30 Ω; after storage at 60°C for 30 days, the impedance is preferably ≤150 Ω, more preferably ≤100 Ω.

[0091] In this invention, the method for preparing the composite positive electrode preferably includes:

[0092] The composite-doped high-nickel large single-crystal ternary layered oxide cathode material is mixed with an electrolyte to obtain a composite cathode.

[0093] In this invention, the preferred mass ratio of the composite-doped high-nickel large single-crystal ternary layered oxide cathode material to the electrolyte is (5-5.4):(4.6-5).

[0094] In this invention, the mixing preferably includes first coarse mixing in a mortar until the white color disappears from the mixture, and then repeatedly kneading the mixture with a grinding rod to obtain a uniform composite positive electrode powder; the coarse mixing time is preferably 1 to 3 minutes, more preferably 2 minutes; the composite kneading time is preferably 20 to 40 minutes, more preferably 30 minutes.

[0095] This invention provides a solid-state battery, comprising: the composite-doped high-nickel large single-crystal ternary layered oxide cathode material described in the above-mentioned technical solution. In this invention, the solid-state battery preferably comprises:

[0096] Electrolyte diaphragm;

[0097] The positive and negative electrodes are respectively disposed on the upper and lower surfaces of the electrolyte membrane.

[0098] In this invention, the electrolyte membrane is preferably composed of Li6PS5Cl; the thickness of the electrolyte membrane is preferably 100-500 μm, more preferably 200-300 μm.

[0099] In this invention, the composition of the positive electrode is preferably the composite-doped high-nickel large single-crystal ternary layered oxide positive electrode material (or the composite electrode described in the above-mentioned technical solution) as described in the technical solution; the areal density of the positive electrode is preferably 5-20 mg / cm³. 2 More preferably 10–15 mg / cm³ 2 .

[0100] In this invention, the composition of the negative electrode is preferably In; the thickness of the negative electrode is preferably 40-60 μm, more preferably 45-55 μm, and most preferably 50 μm.

[0101] In this invention, the method for preparing the solid-state battery preferably includes:

[0102] The electrolyte powder is first pressed into an electrolyte diaphragm;

[0103] After placing the positive electrode component on one surface of the electrolyte membrane, a second pressing is performed to obtain the positive electrode;

[0104] The negative electrode component is placed on the other side of the electrolyte membrane and subjected to a third pressing to assemble a solid-state battery.

[0105] In this invention, the first pressing is preferably carried out in an insulating sleeve, and the pressure of the first pressing is preferably 1 to 3T, more preferably 2T; the pressure of the second pressing is preferably 2 to 4T, more preferably 3T; the pressure of the third pressing is preferably 0.4 to 0.6T, more preferably 0.5T; the solid-state battery is prepared in an argon glove box, and the water partial pressure is preferably ≤0.1ppm and the oxygen partial pressure is preferably ≤0.1ppm.

[0106] The method provided by this invention forms a larger single crystal through a single sintering process, which reduces sintering and crushing costs compared to conventional methods and eliminates water washing pollution. The synergistic effect caused by multiple dopants enables the particles to grow and stabilize the internal and surface of the crystal, thus improving both capacity and rate capability in solid-state batteries.

[0107] Example 1

[0108] A method for preparing a composite-doped high-nickel large single-crystal ternary layered cathode material includes the following steps:

[0109] 4000g Ni 0.9 Co 0.05 Mn 0.05 The (OH)2 precursor and LiOH·H2O were mixed in a molar ratio of 1:1.02, along with 33.7g SrCO3, 16.2g ZrO2 and 34.4g H3BO3. The mixture was stirred evenly in a high-speed mixer for 15 minutes at a speed of 800 r / min to obtain the final mixture.

[0110] The resulting mixture was sintered in a box furnace under an oxygen atmosphere, first at 550℃ for 4 hours, then at 880℃ for 12 hours, and finally at 750℃ for 6 hours, with a heating / cooling rate of 2℃ / min. After cooling to room temperature, it was subjected to air jet milling and sieving to obtain the single-crystal cathode material Li. 1.02 Ni 0.9 Co 0.05 Mn 0.05 A 0.005 B 0.003 C 0.0015 O2.

[0111] Figure 1 The scanning electron microscope (EDS) image of the cathode material prepared in Example 1 shows that Sr, Zr, and B elements are uniformly present in the cathode material. Figure 2 The XRD image of the cathode material prepared in Example 1 shows that in addition to the typical XRD characteristic peaks of ternary materials, there are also characteristic peaks of SrZrO3 in the lattice. Combining these two data points, it can be proved that Sr and Zr have been successfully doped into the lattice, while B remains on the surface as a coating layer.

[0112] Example 2

[0113] Single-crystal cathode materials were prepared according to the method of Example 1, the difference being that Ni was used instead of Ni. 0.80 Co 0.15 Mn 0.05 (OH)2 precursor.

[0114] Example 3

[0115] Single-crystal cathode materials were prepared according to the method of Example 1, the difference being that Ni was used instead of Ni. 0.96 Co 0.02 Mn 0.02 (OH)2 precursor.

[0116] Example 4

[0117] Single-crystal cathode materials were prepared according to the method of Example 1, except that LiNO3 lithium salt was used.

[0118] Example 5

[0119] The single-crystal cathode material was prepared according to the method of Example 1, except that the molar ratio of the precursor to lithium salt was 1:1.05.

[0120] Example 6

[0121] The single-crystal cathode material was prepared according to the method of Example 1, except that 23.7g of SrO was used instead of 33.7g of SrCO3.

[0122] Example 7

[0123] The single-crystal cathode material was prepared according to the method of Example 1, except that 3.4 g of SrCO3 was used instead of 33.7 g of SrCO3.

[0124] Example 8

[0125] The single-crystal cathode material was prepared according to the method of Example 1, except that 2.7g of ZrO2 was used instead of 16.2g of ZrO2.

[0126] Example 9

[0127] The single-crystal cathode material was prepared according to the method of Example 1, except that 23.7g of TiO2 was used to replace 16.2g of ZrO2.

[0128] Example 10

[0129] The single-crystal cathode material was prepared according to the method of Example 1, except that 9.7g of B2O3 was used to replace 34.4g of H3BO3.

[0130] Example 11

[0131] The single-crystal cathode material was prepared according to the method of Example 1, except that 11.5g of H3BO3 was used instead of 34.4g of H3BO3.

[0132] Example 12

[0133] The single-crystal cathode material was prepared according to the method of Example 1, except that 600℃ was used instead of 550℃.

[0134] Example 13

[0135] The single-crystal cathode material was prepared according to the method of Example 1, except that 450°C was used instead of 550°C.

[0136] Example 14

[0137] The single-crystal cathode material was prepared according to the method of Example 1, except that 950℃ was used instead of 880℃.

[0138] Example 15

[0139] The single-crystal cathode material was prepared according to the method of Example 1, except that 850℃ was used instead of 880℃.

[0140] Example 16

[0141] The single-crystal cathode material was prepared according to the method of Example 1, except that 700℃ was used instead of 750℃.

[0142] Example 17

[0143] The single-crystal cathode material was prepared according to the method of Example 1, except that 800℃ was used instead of 750℃.

[0144] Comparative Example 1

[0145] The single-crystal cathode material was prepared according to the method of Example 1, except that sintering at 880°C was not performed.

[0146] Comparative Example 2

[0147] The single-crystal cathode material was prepared according to the method of Example 1, except that SrCO3 was not added.

[0148] Comparative Example 3

[0149] The single-crystal cathode material was prepared according to the method of Example 1, except that ZrO2 was not added.

[0150] Comparative Example 4

[0151] The single-crystal cathode material was prepared according to the method of Example 1, except that H3BO3 was not added.

[0152] Comparative Example 5

[0153] The single-crystal cathode material was prepared according to the method of Example 1, except that only SrCO3 was added as an additive.

[0154] Comparative Example 6

[0155] The single-crystal cathode material was prepared according to the method of Example 1, except that only ZrO2 was added as an additive.

[0156] Comparative Example 7

[0157] The single-crystal cathode material was prepared according to the method of Example 1, except that only H3BO3 was added as an additive.

[0158] Comparative Example 8

[0159] The single-crystal cathode material was prepared according to the method of Example 1. The difference from Example 1 is that H3BO3 was not added during the process of obtaining the mixture. After sintering at 750°C, an equal amount of H3BO3 was added, and then sintered at 300°C for 10 hours.

[0160] Comparative Example 9

[0161] The single-crystal cathode material was prepared according to the method of Example 1. The difference from Example 1 is that H3BO3 was not added during the process of obtaining the mixture. After sintering at 750°C, an equal amount of H3BO3 was added, and then sintered at 500°C for 10 hours.

[0162] The raw materials used in the examples and comparative examples, the amounts of each raw material, and the sintering methods are shown in the table below:

[0163]

[0164]

[0165] Performance testing

[0166] The ternary cathode materials prepared in Example 1 and Comparative Examples 1-7 were subjected to SEM testing, and the results are as follows: Figures 3 to 10 As shown, Figure 1The large single-crystal ternary cathode material prepared in Example 1 has a particle size of 3.2 μm and good particle dispersion, which is beneficial for contact with the solid electrolyte in the solid-state battery. However, the single-crystal ternary cathode prepared in Comparative Example 1 has more surface powder due to the lack of intermediate-temperature surface repair, which affects the first-efficiency performance and cycle life of the solid-state battery. In Comparative Example 2, the particle size is small due to the lack of flux, which is not conducive to dispersion in the solid-state battery. In Comparative Example 3, the particle breakage is very serious due to the lack of crystal structure stabilizer, which is not conducive to cycle performance. In Comparative Example 4, the particle agglomeration is serious due to the lack of surface dopant, which is also not conducive to capacity utilization. In Comparative Example 5, although the crystal size is large due to the addition of flux, the lattice stability is poor and the surface is unstable, resulting in a lot of powder. In Comparative Example 6, the crystal size is small due to the addition of lattice stabilizer, and there is also a lot of powder on the surface. In Comparative Example 7, the crystal size is small and the crystal is unstable due to the addition of surface dopant, but there is less surface powder. In summary, the desired high-nickel large single-crystal ternary cathode material can only be obtained by the simultaneous action of the three dopants.

[0167] The high-nickel large single-crystal ternary cathode materials prepared in the examples and comparative examples were applied in solid-state batteries, and their electrochemical performance was tested; the specific fabrication method of the all-solid-state battery is as follows:

[0168] The positive electrode material and Li6PS5Cl solid electrolyte were weighed according to the mass ratio of 5+x:5-x (0≤x<0.4), and stirred for 1 hour to mix evenly to obtain composite positive electrode powder.

[0169] A certain mass of Li6PS5Cl electrolyte powder was weighed and placed in an insulating sleeve. It was pressed under a pressure of 1-3T to form an electrolyte membrane of 300μm. Then, 10mg of the prepared composite positive electrode powder was placed on one side of the electrolyte layer and pressed further under a pressure of 2-4T to obtain the positive electrode and the electrolyte membrane.

[0170] A 50μm In sheet was placed on the other side of the electrolyte membrane and pressed to 0.5T to assemble a battery. All the above operations were carried out in an argon glove box with a moisture partial pressure ≤0.1ppm and an oxygen partial pressure ≤0.1ppm.

[0171] The battery was charged and discharged using a constant current charge-discharge mode at room temperature, with a voltage range of 1.9–3.7V and a current density of 100 mA / g (0.5C rate) for 100 charge-discharge cycles. The results of the first-week charge specific capacity, first-week discharge specific capacity, first-week coulombic efficiency, 1C discharge capacity, and capacity retention after 100 cycles for the all-solid-state battery are as follows:

[0172]

[0173]

[0174]

[0175] As can be seen, the solid-state batteries assembled from the cathode materials prepared in the examples all exhibited good capacity, first-time efficiency, rate capability, and cycle performance. However, Comparative Example 1, lacking a medium-temperature sintering platform, significantly lagged behind the examples in terms of capacity, rate capability, and cycle performance. Comparative Example 2, lacking flux, had small crystal sizes and insufficient contact with the solid electrolyte, resulting in poor rate performance. Comparative Example 3, lacking stabilizer, experienced structural decomposition during cycling, leading to poor cycle performance. Comparative Example 4, lacking surface dopant, had high surface impedance and numerous side reactions, resulting in poor rate and cycle performance. Comparative Example 5, doped only with flux, had large crystal sizes, but both the surface and bulk phases were unstable, resulting in poor first-time efficiency, rate capability, and cycle performance. Comparative Example 6, with only stabilizer, had small grains and high surface impedance, resulting in good cycle performance but poor capacity and rate capability. Comparative Example 7, with only surface dopant, had small grain sizes and unstable structures, resulting in good rate performance but poor capacity and cycle performance. In Comparative Examples 8 and 9, because surface dopants were added during the second sintering, there was no flux to reduce surface energy during sintering; only surface coating occurred, instead of the surface coating plus near-surface doping in the examples. Therefore, the resulting cathode materials exhibited slightly inferior electrochemical performance compared to the examples. It can be seen that the large single-crystal high-nickel ternary materials with large grain size, high crystal stability, and stable surface obtained through the examples perform well in solid-state batteries, while the comparative examples, regardless of the missing dopant, could not achieve good performance.

[0176] The method provided by this invention forms a larger single crystal through a single sintering process, which reduces sintering and crushing costs compared to conventional methods and eliminates water washing pollution. The synergistic effect caused by multiple dopants enables the particles to grow and stabilize the internal and surface of the crystal, thus improving both capacity and rate capability in solid-state batteries.

[0177] While the invention has been described and illustrated with reference to specific embodiments thereof, such description and illustration are not intended to limit the invention. It will be readily understood by those skilled in the art that various changes may be made to suit particular circumstances, materials, compositions, substances, methods, or processes to the objectives, spirit, and scope of this application without departing from the true spirit and scope of the invention as defined by the appended claims. All such modifications are intended to be within the scope of the appended claims. Although the methods disclosed herein have been described with reference to specific operations performed in a particular order, it should be understood that these operations may be combined, subdivided, or reordered to form equivalent methods without departing from the teachings of the invention. Therefore, unless specifically indicated herein, the order and grouping of operations are not a limitation of this application.

Claims

1. A composite-doped high-nickel large single-crystal ternary layered oxide cathode material, comprising: The substrate contains a bulk flux, a lattice stabilizer, and lithium nickel cobalt manganese oxide; A coating layer disposed on the surface of the substrate, the coating layer containing a surface dopant; The chemical formula of the composite-doped high-nickel large single-crystal ternary layered oxide cathode material is shown in Formula I: Li a Ni x Co y Mn z A α B β C γ O2 Formula I; In Equation I, 0.98 ≤ a ≤ 1.05, 0.80 ≤ x ≤ 0.98, 0.05 ≤ y ≤ 0.15, z = 1 - xy. 0.0005 ≤ α ≤ 0.01, 0.0005 ≤ β ≤ 0.01, 0.0005 ≤ γ ≤ 0.01; A is selected from metallic elements in bulk fluxes; B is selected from metallic elements in lattice stabilizers; C is selected from surface dopant elements; The bulk flux is selected from one or more of strontium oxide, strontium carbonate, strontium nitrate, and strontium hydroxide; The lattice stabilizer is selected from one or more of metal oxides, hydroxides, and chlorides; the metal is selected from one or more of zirconium, titanium, tungsten, and yttrium. The surface dopant is selected from boron-containing substances; The composite doped high-nickel large single-crystal ternary layered oxide positive electrode material is subjected to XRD detection, and I 003 / I 104 The c / a value is 4.93-4.94, the FWHM （003） The lithium-nickel mixing rate is 1-3%. The mass content of Li2CO3 in the composite doped high-nickel large single-crystal ternary layered oxide positive electrode material is ≤3000 ppm, the mass content of LiOH is ≤5000 ppm, and the mass content of Free Li + is ≤2000 ppm. The high-nickel large single-crystal ternary layered oxide cathode material is used in solid-state batteries.

2. The composite doped high-nickel large single-crystal ternary layered oxide cathode material of claim 1, characterized in that, The mass of the bulk flux is 500~10000 ppm of the mass of lithium nickel cobalt manganese oxide.

3. The composite doped high-nickel large single-crystal ternary layered oxide cathode material of claim 1, wherein, The mass of the lattice stabilizer is 500~10000 ppm of the mass of lithium nickel cobalt manganese oxide.

4. The composite doped high-nickel large single-crystal ternary layered oxide cathode material of claim 1, wherein, The mass of the surface dopant is 500~10000 ppm of the mass of lithium nickel cobalt manganese oxide.

5. The composite doped high-nickel large single-crystal ternary layered oxide cathode material of claim 1, wherein, The composite-doped high-nickel large single-crystal ternary layered oxide cathode material has a D50 of 4~10μm, a particle diameter of 1.5~25μm, and a SPAN of 0.8~1.

5. The specific surface area of ​​the composite-doped high-nickel large single-crystal ternary layered oxide cathode material is 0.2~0.4 cm². 2 / g; compacted density is 3.2~3.5g / cm³ 3 .

6. A method for preparing the composite-doped high-nickel large single-crystal ternary layered oxide cathode material according to claim 1, comprising: The additives, lithium salts, and lithium nickel cobalt manganese oxide precursor were mixed to obtain a mixture; The mixture was subjected to low-temperature sintering, high-temperature sintering and medium-temperature sintering in sequence to obtain the sintered product; The sintered product is not washed with water to obtain a composite-doped high-nickel large single crystal ternary layered oxide cathode material. The additives include: Bulk flux, lattice stabilizer and surface dopant.

7. The method of claim 6, wherein, The low-temperature sintering temperature is 450~600℃, and the low-temperature sintering time is 2~4h; the high-temperature sintering temperature is 850~950℃, and the high-temperature sintering time is 5~10h; the medium-temperature sintering temperature is 700~800℃, and the medium-temperature sintering time is 5~10h.

8. A composite positive electrode, comprising: The composite-doped high-nickel large single-crystal ternary layered oxide cathode material according to any one of claims 1 to 5, or the composite-doped high-nickel large single-crystal ternary layered oxide cathode material and electrolyte prepared by the preparation method according to claim 6 or 7.

9. A solid-state battery, comprising: The composite-doped high-nickel large single-crystal ternary layered oxide cathode material according to any one of claims 1 to 5, or the composite-doped high-nickel large single-crystal ternary layered oxide cathode material prepared by the preparation method according to claim 6 or 7.

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