High-voltage composite positive electrode material and preparation method and application thereof

Abstract

The invention relates to the technical field of lithium ion batteries, and particularly discloses a high-voltage composite positive electrode material as well as a preparation method and application thereof. A preparation method of the high-voltage composite positive electrode material disclosed by the invention comprises the following steps: co-precipitating a nickel source, a cobalt source, a manganese source and a mixed solution containing a first doping element, a second doping element and a third doping element to obtain a precursor; and S2, mixing the precursor with a lithium source, and sintering to obtain the high-voltage positive electrode material, and S3, crushing the high-voltage positive electrode material, repairing the crushed high-voltage positive electrode material through mixed repairing gas, and cooling and sieving the crushed high-voltage positive electrode material to obtain the high-voltage composite positive electrode material. According to the invention, a high-entropy stable bulk phase is constructed through multi-element co-doping, and a surface interface is optimized in combination with a unique gas phase repair technology, so that the problem that the cycling stability and rate capability of the positive electrode material are sharply deteriorated under high voltage is synergistically solved, and the prepared positive electrode material has high voltage, high capacity and long cycle life.

Description

A high-voltage composite cathode material, its preparation method and application Technical Field

[0001] This invention relates to the field of lithium-ion batteries, specifically to a high-voltage composite cathode material, its preparation method, and its application. Background Technology

[0002] High-voltage, low-nickel ternary cathode materials have become a research hotspot in the power battery field due to their superior thermal stability, structural stability, and lower production cost compared to high-nickel cathode materials. By increasing the charging cut-off voltage of low-nickel ternary cathode materials (typically from 4.2-4.3V to 4.4-4.6V), their capacity potential can be fully exploited, bringing their energy density close to or even comparable to that of high-nickel cathode materials. However, under high-voltage conditions, the intrinsic structural instabilities of the bulk phase and interfaces of the cathode material are drastically amplified, leading to a rapid deterioration in cycle life, rate performance, and safety. Existing technologies mainly modify these materials through bulk doping and surface coating, but a series of insurmountable defects remain. At high voltages (>4.4V vs. Li...), the capacity potential of these materials can be significantly increased. + In the deep delithiation state of / Li, Ni in the material 3+ / Ni 4+ Ni has extremely strong oxidizing properties, easily causing adjacent lattice oxygen to lose electrons and form O2 precipitation. The generation of oxygen vacancies triggers the migration of transition metal (TM) ions (especially Ni ions) to the lithium layer, causing an irreversible transformation of the layered structure into a spinel or rock salt phase (without electrochemical activity). This phase transition is the fundamental cause of capacity decay and increased internal resistance. In addition, the highly active oxidized Ni... 4+ The deposited lattice oxygen directly catalyzes the oxidative decomposition of the electrolyte, forming a thick, uneven, and highly impedance cathode electrolyte interphase (CEI) film on the surface of the cathode material. Simultaneously, the deposition of lattice oxygen on the material surface triggers an irreversible phase transition, forming an electrochemically inert rock salt shell that severely hinders lithium-ion diffusion.

[0003] Traditional single or dual-element doping can stabilize the crystal structure to some extent, and some studies have proposed using Mo and F co-doping to suppress phase transitions. However, the bonding strength formed by this low-entropy doping method is limited, and the distribution of dopants is uneven. Under long-term cycling and high-pressure shocks, its stabilizing effect gradually weakens, and it cannot fundamentally suppress severe lattice oxygen loss and structural collapse. Surface coating (such as Al2O3, ZrO2, etc.) is a common method to improve interface stability. Some studies have used Al2O3 to coat NCM523, but this coating layer is a physical barrier with weak bonding force to the bulk, and it is prone to cracking and failure under long-term cyclic volume expansion / contraction stress. More importantly, the coating layer usually has poor ionic conductivity, which, although suppressing side reactions, often comes at the cost of sacrificing rate performance. Summary of the Invention

[0004] This invention provides a high-voltage composite cathode material, its preparation method, and its application to solve the above-mentioned problems.

[0005] In a first aspect, the present invention provides a method for preparing a high-voltage composite cathode material, comprising the following steps: S1, co-precipitating a nickel source, a cobalt source, and a manganese source with a mixture containing a first dopant element, a second dopant element, and a third dopant element to obtain a precursor; S2, sintering the precursor with a lithium source to obtain a high-voltage cathode material; S3, pulverizing the high-voltage cathode material, repairing it with a mixed repair gas, cooling and sieving to obtain a high-voltage composite cathode material; wherein the first dopant element comprises at least one of 4-5 valent metal cations; the second dopant element comprises at least one of 3 valent metal cations; the third dopant element comprises at least one of 1-2 valent metal cations; and the mixed repair gas comprises a weak reducing gas and a weak oxidizing gas.

[0006] In some optional embodiments, the first dopant element, the second dopant element, and the third dopant element are derived from soluble salts or oxides containing the dopant elements described above; optionally, the soluble salt includes at least one of metal nitrates, metal sulfates, metal acetates, and metal carbonates.

[0007] In some optional embodiments, the molar ratio of the nickel source, cobalt source, and manganese source is (0.5-0.7):(0.1-0.3):(0.1-0.3); in some optional embodiments, the molar ratio of the first dopant element, the second dopant element, the third dopant element, and the nickel source is (0.001-0.05):(0.001-0.02):(0.001-0.02):(0.6-0.7); optionally, the molar ratio of the first dopant element, the second dopant element, and the third dopant element is the same.

[0008] In some alternative implementations, the first dopant element includes Ti. 4+ Zr 4+ Sn 4+ 、Nb 5+ Ta 5+ At least one of the following; in some alternative embodiments, the second doping element includes Al. 3+ Cr 3+ Fe 3+ Ga 3+ At least one of the following; in some optional embodiments, the third doping element includes Na. + K + Mg 2+ At least one of them.

[0009] In some alternative implementations, the repair temperature is 250-400°C and the time is 1-4 hours.

[0010] In some optional embodiments, the volume ratio of the weak reducing gas to the weak oxidizing gas in the mixed remediation atmosphere is (4-10):1.

[0011] In some optional embodiments, the weak reducing gas includes a mixture of reducing gas and inert gas; optionally, the reducing gas accounts for 1%-5% of the volume fraction of the inert gas; optionally, the inert gas includes at least one of nitrogen, helium, and argon; optionally, the reducing gas includes at least one of CO, NH3, and H2; in some optional embodiments, the weak oxidizing gas includes a mixture of oxidizing gas and inert gas; optionally, the oxidizing gas accounts for 1%-5% of the volume fraction of the argon gas; optionally, the oxidizing gas includes at least one of O2 and NO2.

[0012] In some optional embodiments, the molar ratio of Li in the lithium source to the total amount of nickel, cobalt, and manganese metal in the precursor is (1.0-1.05):1.

[0013] In some optional embodiments, the sintering temperature is 900-1000℃ and the time is 10-15h; optionally, the sintering further includes pre-firing; the pre-firing temperature is 500-700℃ and the time is 4-6h; in some optional embodiments, the sintering atmosphere includes a pure oxygen atmosphere.

[0014] In some optional embodiments, the nickel source includes at least one of nickel sulfate, nickel nitrate, and nickel acetate; in some optional embodiments, the cobalt source includes at least one of cobalt sulfate, cobalt nitrate, and cobalt acetate; in some optional embodiments, the manganese source includes at least one of manganese sulfate, manganese nitrate, and manganese acetate; in some optional embodiments, the lithium source includes at least one of lithium carbonate and lithium hydroxide.

[0015] Secondly, the present invention provides a lithium-ion battery comprising a high-voltage composite cathode material prepared by the above-described preparation method.

[0016] Those skilled in the art will understand that the lithium-ion battery provided by the present invention may include structural components such as an electrolyte, a positive electrode, a negative electrode, a separator, and a casing. During the charging and discharging process, lithium ions repeatedly insert and extract between the positive and negative electrode. The electrolyte acts as a conductor between the positive and negative electrode. The separator is disposed between the positive and negative electrode, primarily to prevent short circuits between the positive and negative electrodes, while simultaneously allowing lithium ions to pass through.

[0017] As an example, the positive electrode sheet includes a positive current collector and a positive active layer. The positive current collector has two surfaces opposite each other in its own thickness direction, and the positive active layer is disposed on either or both of the opposite surfaces of the positive current collector. The materials, composition, and manufacturing methods of the positive electrode sheet used in the lithium-ion battery of the present invention may include any techniques disclosed in the prior art.

[0018] As an example, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer. The negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode active layer is disposed on either or both of the opposing surfaces of the negative electrode current collector. The materials, composition, and manufacturing methods of the negative electrode sheet used in the lithium-ion battery of the present invention may include any techniques disclosed in the prior art.

[0019] The material and shape of the separator used in the lithium-ion battery of the present invention are not particularly limited, and may include any technology disclosed in the prior art.

[0020] The electrolyte used in the lithium-ion battery of the present invention may also include any technology disclosed in the prior art.

[0021] This invention does not specifically limit the preparation method of lithium-ion batteries; lithium-ion batteries can be prepared using conventional preparation methods in the art. For example, positive electrode sheets, separators, and negative electrode sheets are stacked sequentially, with the separator located between the positive and negative electrode sheets. A cell is obtained through stacking or winding processes, and then the lithium-ion battery of this invention is obtained through baking, electrolyte injection, formation, and packaging.

[0022] Thirdly, the present invention provides an electrical device comprising the above-described lithium-ion battery.

[0023] It is understood that in the electrical equipment provided by the present invention, the lithium-ion battery can be used as a power source for the electrical equipment, or as an energy storage unit for the electrical equipment. The electrical equipment may be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0024] The technical solution of this invention has the following advantages: 1. The preparation method of a high-voltage composite cathode material provided by this invention includes the following steps: S1, co-precipitating a nickel source, a cobalt source, a manganese source, and a mixture containing a first dopant element, a second dopant element, and a third dopant element to obtain a precursor; S2, sintering the precursor with a lithium source to obtain a high-voltage cathode material; S3, pulverizing the high-voltage cathode material, repairing it with a mixed repair gas, cooling and sieving to obtain a high-voltage composite cathode material; the first dopant element includes at least one of 4-5 valent metal cations; the second dopant element includes at least one of 3 valent metal cations; the third dopant element includes at least one of 1-2 valent metal cations; the mixed repair gas includes a weak reducing gas and a weak oxidizing gas. The first dopant element is mainly used to replace the transition metal site (TM site), and the second dopant element can directly replace Co. 3+ or Ni 3+ It can effectively alleviate lattice distortion and cation mixing, thereby stabilizing the crystal structure; the third doping element is located in the lithium layer and is mainly used to replace Li ions, which can effectively suppress phase transitions during cycling.

[0025] This invention utilizes the aforementioned doping elements to form a high-entropy bulk phase. Its high-entropy effect significantly reduces the Gibbs free energy, thermodynamically suppressing lattice oxygen evolution and the irreversible phase transition of the layered-spinel-rock salt phase. This achieves global and intrinsic stability of the bulk phase structure and greatly increases the activation energy of the phase transition. Simultaneously, a low-temperature vapor phase repair technique is employed to address the core challenge of oxygen vacancies pre-existing on the material surface forming the high-entropy bulk phase. Through a mechanism of "mild reduction activation followed by oxidation filling," the defect sites of catalytic activity are transformed into electrochemically stable complete lattices. This eliminates the trigger points for interfacial side reactions under high pressure at the source, providing robust and stable support for interfacial repair. The repaired surface structure is more durable, and the complete interface provides further protection for the high-entropy bulk phase, effectively isolating it from electrolyte erosion and maintaining its high-entropy stability for a long time. This simultaneously overcomes the two major failure mechanisms of the bulk phase and the interface.

[0026] In summary, the preparation method provided by this invention, while systematically introducing a high-entropy bulk phase into the ternary cathode material, employs low-temperature vapor phase repair technology, which effectively improves the problem that under high pressure conditions, the intrinsic structural instability of the bulk phase and interface of the cathode material is drastically amplified, leading to a rapid deterioration in its cycle life, rate performance, and safety.

[0027] 2. The mixed repair atmosphere in the preparation method provided by this invention, wherein a weakly reducing gas gently reduces the high-valence Ni on the surface. 3+ / Ni 4+This causes some of the oxygen vacancies to detach from the crystal lattice, exposing and activating them. During the oxidation process, the weak oxidizing gas immediately reacts with the activated vacancies and the surrounding metal atoms, refilling the oxygen vacancies and thus repairing the surface structure.

[0028] 3. The lithium-ion battery and electrical equipment provided by the present invention have the same advantages as the above-mentioned high-voltage composite cathode materials because they are prepared by the method provided by the present invention. They will not be described again here.

[0029] Additional aspects and advantages of the embodiments of the present invention will be described and shown in part in the following description, or illustrated by practice of the embodiments of the present invention. Detailed Implementation

[0030] The following embodiments are provided to better understand the present invention, but the following embodiments 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 scope of protection of the present invention.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having” and any variations thereof in the text of this application are intended to cover non-exclusive inclusion.

[0032] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The "scope" disclosed in this application is defined in the form of a lower limit and an upper limit, whereby a given scope is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular scope. Scopes defined in this manner may include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a scope. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein, and "0-5" is merely a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer greater than or equal to 2, it is equivalent to disclosing that the parameter can be, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0033] In the description of the embodiments of this application, the term "and / or" is merely a description of the relationship between related objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone.

[0034] In the description of the embodiments of this application, the term "at least one" refers to one or more (including two).

[0035] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0036] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0037] Example 1 This example provides a method for preparing a high-voltage composite cathode material. The specific steps and parameter settings are as follows: S1, a ternary mixed solution is obtained by mixing a NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O salt solution (Ni:Co:Mn molar ratio = 0.6:0.2:0.2); the ternary mixed solution is then mixed with a mixed solution containing TiO2, ZrO2, Nb2O5, Al2O3, and Mg(OH)2 and co-precipitated at 60℃ for 10 h to obtain a precursor; the Ti in the mixed solution... 4+ Zr 4+ 、Nb 5+ Al 3+ Mg 2+ The molar ratio of the metal salt to NiSO4 in the ternary mixed solution is 0.005:0.005:0.005:0.005:0.005:0.6; S2, the precursor and Li2CO3 are pre-calcined at 600℃ for 6h in a pure oxygen atmosphere, and then sintered at 940℃ for 10h, and cooled with the furnace to obtain a high-voltage cathode material; the molar ratio of Li in Li2CO3 to the total amount of nickel, cobalt and manganese metal in the precursor is 1.04:1; S3, the high-voltage cathode material is air-jet pulverized and placed in a box furnace, and a mixed repair atmosphere composed of a weak reducing gas (CO accounting for 5% of Ar volume fraction) and a weak oxidizing gas (O2 accounting for 5% of Ar volume fraction) in a volume ratio of 10:1 is introduced, and repaired at 350℃ for 4h. After natural cooling and sieving, a high-voltage composite cathode material is obtained.

[0038] Example 2 This example provides a method for preparing a high-voltage composite cathode material. The only difference from Example 1 is that, in S1, the Ti in the mixture... 4+ Zr 4+ 、Nb 5+ Al 3+ Mg 2+ The molar ratio of the metal salt to NiSO4 in the ternary mixed solution is 0.01:0.01:0.01:0.01:0.01:0.6; the remaining steps are the same as in Example 1.

[0039] Example 3 This example provides a method for preparing a high-voltage composite cathode material. The only difference from Example 1 is that, in S1, the Ti in the mixture... 4+ Zr 4+ 、Nb 5+ Al 3+ Mg 2+ The molar ratio of the metal salt to NiSO4 in the ternary mixed solution was 0.015:0.015:0.015:0.015:0.015:0.6; the remaining steps were the same as in Example 1.

[0040] Example 4 This example provides a method for preparing a high-voltage composite cathode material. The only difference from Example 1 is that in S3, a mixed repair atmosphere composed of a weak reducing gas (CO accounting for 5% of the volume fraction of Ar) and a weak oxidizing gas (O2 accounting for 5% of the volume fraction of Ar) in a volume ratio of 8:1 is introduced; the remaining steps are the same as in Example 1.

[0041] Example 5 This example provides a method for preparing a high-voltage composite cathode material. The only difference from Example 1 is that in S3, a mixed repair atmosphere composed of a weak reducing gas (CO accounting for 5% of the volume fraction of Ar) and a weak oxidizing gas (O2 accounting for 5% of the volume fraction of Ar) in a volume ratio of 6:1 is introduced; the remaining steps are the same as in Example 1.

[0042] Example 6 This example provides a method for preparing a high-voltage composite cathode material. The only difference from Example 1 is that in S3, a mixed repair atmosphere composed of a weak reducing gas (CO accounting for 5% of the volume fraction of Ar) and a weak oxidizing gas (O2 accounting for 5% of the volume fraction of Ar) in a volume ratio of 4:1 is introduced; the remaining steps are the same as in Example 1.

[0043] Example 7 This example provides a method for preparing a high-voltage composite cathode material, differing from Example 1 only in that: in S1, the molar ratio of Ni:Co:Mn in the ternary mixed solution is 0.5:0.2:0.3; the molar ratio of Ti in the mixed solution is... 4+ Zr 4+ 、Nb 5+ Al 3+ Mg 2+ The molar ratio of the metal salt to NiSO4 in the ternary mixed solution is 0.02:0.01:0.02:0.001:0.002:0.6; in S2, it is first pre-calcined at 700℃ for 4h, and then sintered at 1000℃ for 10h; the molar ratio of Li2CO3 to the precursor is 1.05:1; in S3, a mixed repair atmosphere composed of a weak reducing gas (CO accounting for 1% of Ar volume fraction) and a weak oxidizing gas (O2 accounting for 5% of Ar volume fraction) in a volume ratio of 4:1 is used for repair at 400℃ for 1h; the remaining steps are the same as in Example 1.

[0044] Example 8 This example provides a method for preparing a high-voltage composite cathode material, differing from Example 1 only in that: in S1, the molar ratio of Ni:Co:Mn in the ternary mixed solution is 0.7:0.1:0.2; the molar ratio of Ti in the mixed solution is... 4+ Zr 4+ 、Nb 5+ Al 3+ Mg 2+The molar ratio of the metal salt to NiSO4 in the ternary mixed solution is 0.0003:0.0004:0.0003:0.02:0.001:0.7; in S2, it is first pre-calcined at 500℃ for 6 hours, and then sintered at 900℃ for 15 hours; the molar ratio of Li2CO3 to the precursor is 1:1; in S3, a mixed repair atmosphere composed of a weak reducing gas (CO accounting for 5% of Ar volume fraction) and a weak oxidizing gas (O2 accounting for 1% of Ar volume fraction) in a volume ratio of 10:1 is used for repair at 250℃ for 4 hours; the remaining steps are the same as in Example 1.

[0045] Comparative Example 1 This comparative example provides a method for preparing a high-voltage composite cathode material. The only difference from Example 1 is that in S1, the first doping element, the second doping element, and the third doping element are not added; the remaining steps are the same as in Example 1.

[0046] Comparative Example 2 provides a method for preparing a high-voltage composite cathode material. The only difference from Example 1 is that in S3, no repair is performed, and the material is directly passed through air jet pulverization and then sieved; the remaining steps are the same as in Example 1.

[0047] Comparative Example 3 provides a method for preparing a high-voltage composite cathode material, which differs from Example 1 only in that: in S1, Ti is used... 4+ 、Nb 5+ 、 Zr 4+ Replace with an equimolar amount of Al 3+ The remaining steps are the same as in Example 1.

[0048] Comparative Example 4 provides a method for preparing a high-voltage composite cathode material, which differs from Example 1 only in that: in S1, Al is... 3+ Replace with an equimolar amount of Mg 2+ The remaining steps are the same as in Example 1.

[0049] Comparative Example 5 provides a method for preparing a high-voltage composite cathode material, which differs from Example 1 only in that: in S1, Mg is... 2+ Replace with an equimolar amount of Al 3+ The remaining steps are the same as in Example 1.

[0050] Comparative Example 6 provides a method for preparing a high-voltage composite cathode material. The only difference from Example 1 is that in S3, the weak reducing gas is replaced with an equal volume of weak oxidizing gas; the remaining steps are the same as in Example 1.

[0051] Comparative Example 7 provides a method for preparing a high-voltage composite cathode material. The only difference from Example 1 is that in S3, the weak oxidizing gas is replaced with an equal volume of weak reducing gas; the remaining steps are the same as in Example 1.

[0052] In Experiment 1, the high-voltage composite cathode materials obtained from each embodiment and comparative example were applied to a lithium-ion battery, and then their electrochemical performance was tested.

[0053] The preparation method of the lithium-ion battery includes the following steps: the positive electrode material prepared above is mixed with active material, conductive agent and binder in a ratio of 8:1:1 to form a slurry and coated on the current collector (aluminum foil). In a glove box filled with inert gas (argon), the components are stacked from bottom to top in the following order: negative electrode shell - spring sheet - gasket - lithium sheet (counter electrode) - electrolyte - separator - electrolyte - working electrode sheet - positive electrode shell. Then the entire assembly is moved to a button cell sealing machine, and sufficient pressure is applied to make the upper and lower battery shells tightly snap together to complete the seal, forming a standard CR2032 button cell. Finally, the battery is taken out and allowed to stand for aging before electrochemical testing.

[0054] The specific methods for electrical performance testing are as follows: (1) First-cycle charge and discharge performance test: The assembled coin cell battery is charged and discharged for the first time at a rate of 0.1C. The first-cycle charging capacity and the first-cycle discharging capacity are recorded, and the first-cycle coulombic efficiency (first efficiency) is calculated.

[0055] The Coulomb efficiency for the first lap is calculated as follows: .

[0056] Where: ICE is the initial coulombic efficiency; D1 is the initial discharge capacity at a specified rate (e.g., 0.1C); and C1 is the initial charge capacity at the same rate.

[0057] (2) Rate performance test: The assembled coin cell battery was charged and discharged at constant currents of 0.1 C and 5 C in the voltage range of 3.0V to 4.4V, with a cutoff voltage of 4.4V. (3) Cycle stability test: The assembled coin cell battery was charged and discharged 100 times at a constant current of 1C in the voltage range of 3.0V to 4.4V.

[0058] The specific results of the electrical performance test are shown in Table 1: Table 1 Electrical Performance Test Data

[0059] Experimental results show that at a 0.1C rate, the first-cycle discharge capacity of the coin cells prepared with the cathode materials of Examples 1-6 is in the range of 167.2 mAh / g-170.2 mAh / g, which is higher than that of the comparative example (153.1 mAh / g-160.1 mAh / g); the first-cycle charging capacity of the coin cells prepared with the cathode materials of Examples 1-6 is in the range of 184.4 mAh / g-189.8 mAh / g, which is higher than that of the comparative example (175.6 mAh / g-183.6 mAh / g); the first-cycle coulombic efficiency of the coin cells prepared with the cathode materials of Examples 1-6 is in the range of 89.7%-90.9%, which is higher than that of the comparative example (86.3%-87.6%); and the 5C rate capacity of the coin cells prepared with the cathode materials of Examples 1-6 is 143.2 mAh / g. Within the range of 147.2 mAh / g, the positive electrode materials prepared in Examples 1-6 all showed higher 100-cycle retention rates than the comparative examples (120.7 mAh / g-130.5 mAh / g). The coin cells made from the positive electrode materials prepared in Examples 1-6 had 100-cycle retention rates of 92.0%-95.1%, which were higher than the comparative examples (85.5%-87.5%). Among them, Example 7 had a slightly lower discharge capacity due to its low nickel content, which is the main contributor to capacity. In Example 8, the nickel content was higher, so the capacity increased significantly, but the cycle retention rate decreased. However, due to the use of the multi-element co-doping and specific mixed atmosphere (CO / O2) post-repair treatment techniques in this invention, the first-cycle charge-discharge capacity, coulombic efficiency, 5C high-rate discharge capacity, and cycle stability of the material were all better than those of the comparative examples.

[0060] Therefore, the high-voltage composite cathode material provided by this invention, through the synergistic effect of multi-element co-doping and post-treatment in a specific mixed atmosphere (CO / O2), can significantly improve the first-cycle charge-discharge capacity, coulombic efficiency, 5C high-rate discharge capacity and cycle stability of the material compared with undoped or unrepaired samples, proving that this composite modification strategy effectively optimizes the high-voltage electrochemical performance of the material.

[0061] 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 method for preparing a high-voltage composite cathode material, characterized in that, Includes the following steps: S1, co-precipitate the nickel source, cobalt source, and manganese source with a mixture containing the first doping element, the second doping element, and the third doping element to obtain the precursor; S2, the precursor is mixed with a lithium source and sintered to obtain a high-voltage cathode material; S3, the high-voltage cathode material is pulverized, repaired by a mixed repair gas, cooled and sieved to obtain a high-voltage composite cathode material; the first doping element includes at least one of 4-5 valent metal cations; the second doping element includes at least one of 3 valent metal cations; the third doping element includes at least one of 1-2 valent metal cations; the mixed repair gas includes a weak reducing gas and a weak oxidizing gas.

2. The method for preparing the high-voltage composite cathode material according to claim 1, characterized in that, The molar ratio of the nickel source, cobalt source, and manganese source is (0.5-0.7):(0.1-0.3):(0.1-0.3); and / or, the molar ratio of the first dopant element, the second dopant element, the third dopant element, and the nickel source is (0.001-0.05):(0.001-0.02):(0.001-0.02):(0.6-0.7).

3. The method for preparing the high-voltage composite cathode material according to claim 1 or 2, characterized in that, The first doping element includes Ti 4+ Zr 4+ Sn 4+ 、Nb 5+ Ta 5+ At least one of the following; and / or, the second doping element includes Al. 3+ Cr 3+ Fe 3+ Ga 3+ At least one of the following; and / or, the third doping element includes Na. + K + Mg 2+ At least one of them.

4. The method for preparing the high-voltage composite cathode material according to any one of claims 1-3, characterized in that, The repair temperature is 250-400℃, and the time is 1-4 hours.

5. The method for preparing the high-voltage composite cathode material according to any one of claims 1-4, characterized in that, The volume ratio of the weak reducing gas to the weak oxidizing gas in the mixed remediation gas is (4-10):

1.

6. The method for preparing the high-voltage composite cathode material according to any one of claims 1-5, characterized in that, The weak reducing gas includes a mixture of reducing gas and inactive gas; and / or, the weak oxidizing gas includes a mixture of oxidizing gas and inactive gas.

7. The method for preparing the high-voltage composite cathode material according to any one of claims 1-6, characterized in that, The molar ratio of Li in the lithium source to the total amount of nickel, cobalt and manganese metal in the precursor is (1.0-1.05):

1.

8. The method for preparing the high-voltage composite cathode material according to any one of claims 1-7, characterized in that, The sintering temperature is 900-1000℃ and the time is 10-15h; and / or the sintering atmosphere includes a pure oxygen atmosphere.

9. A lithium-ion battery, characterized in that, The high-voltage composite cathode material prepared by the preparation method according to any one of claims 1-8.

10. An electrical appliance, characterized in that, Including the lithium-ion battery as described in claim 9.

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