Lithium supplementing agent, preparation method thereof and lithium ion battery

Abstract

This application discloses a lithium replenishing agent and its preparation method, as well as a lithium-ion battery. The lithium replenishing agent comprises a lithium-rich transition metal oxide, wherein the chemical formula of the lithium-rich transition metal oxide satisfies: Li w Co x M y Q z T u O4, wherein the M element includes at least one of Zn, Mg, Cu, and Ca, the Q element includes at least one of Fe and B, and the T element includes at least one of Nb, Ta, Al, Zr, and Ti; 5.2≤w≤6.12, 0.4≤x≤0.85, 0.05≤y≤0.5, 0.4≤x+y≤0.9, 0.05≤z≤0.55, 0.01≤u≤0.05, x+y+z+u=1; the lithium replenishing agent is assembled into a coin cell, and during the first week of charging, the differential capacity curve of the coin cell has a first characteristic peak between 3.0V and 3.45V, and a second characteristic peak between 3.67V and 4.1V, and the ratio of the peak intensity of the second characteristic peak to the peak intensity of the first characteristic peak is 0.0002~0.11. Therefore, this lithium replenishing agent has high air stability and produces less gas, which can effectively improve the first-week charging specific capacity and safety performance of lithium-ion batteries.

Description

Technical Field

[0001] This application relates to the field of lithium battery technology, specifically to lithium replenishing agents and their preparation methods, and lithium-ion batteries. Background Technology

[0002] In recent years, to meet the increasingly stringent requirements for energy density and cycle life of lithium-ion batteries in fields such as electric vehicles and large-scale energy storage, pre-lithiation (lithiation replenishment) technology has become a key path to break through current battery performance. The core of pre-lithiation technology lies in introducing an additional active lithium source during battery manufacturing to compensate for the irreversible lithium-ion loss caused by the formation of a solid electrolyte interphase film during the first charge and discharge process.

[0003] From a technological perspective, pre-lithiation technology can be divided into two main categories: positive electrode pre-lithiation and negative electrode pre-lithiation. Negative electrode pre-lithiation typically uses lithium powder and lithium foil. While these materials offer high lithium replenishment efficiency, the active lithium metal presents serious safety risks and process bottlenecks. In contrast, positive electrode pre-lithiation boasts advantages such as simpler processes, higher safety, and better compatibility with existing production lines, gradually becoming the mainstream direction for industrialization. Adding sacrificial lithium replenishment additives is a common method in positive electrode pre-lithiation, and lithium-rich transition metal oxides like Li6CoO4 are favored due to their high theoretical specific capacity (814 mAh g⁻¹). -1 Its low decomposition potential (3.2V~4.5V) has attracted widespread attention.

[0004] It should be noted that the above statements are only used to provide background information related to this application and do not necessarily constitute prior art. Summary of the Invention

[0005] In a first aspect of this application, a lithium supplement agent is proposed, comprising a lithium-rich transition metal oxide, wherein the chemical formula of the lithium-rich transition metal oxide satisfies: Li w Co x M y Q z T uO4, wherein the M element includes at least one of Zn, Mg, Cu, and Ca, the Q element includes at least one of Fe and B, and the T element includes at least one of Nb, Ta, Al, Zr, and Ti; 5.2≤w≤6.12, 0.4≤x≤0.85, 0.05≤y≤0.5, 0.4≤x+y≤0.9, 0.05≤z≤0.55, 0.01≤u≤0.05, x+y+z+u=1; the lithium replenishing agent is assembled into a coin cell, and during the first week of charging, the differential capacity curve of the coin cell has a first characteristic peak between 3.0V and 3.45V, and a second characteristic peak between 3.67V and 4.1V, and the ratio of the peak intensity of the second characteristic peak to the peak intensity of the first characteristic peak is 0.0002~0.11. Therefore, this lithium replenishing agent has high air stability and produces less gas, which can effectively improve the first-week charging specific capacity and safety performance of lithium-ion batteries.

[0006] In some embodiments of this application, the lithium replenishment agent is assembled into a coin cell. During the first week of charging, the differential capacity curve of the coin cell exhibits a second characteristic peak between 3.75V and 4.1V. Therefore, the rightward shift of the second characteristic peak indicates that the high-pressure oxygen reduction reaction is delayed, which helps to further reduce the tendency for lattice oxygen release.

[0007] In some embodiments of this application, the ratio of the peak intensity of the second characteristic peak to the peak intensity of the first characteristic peak is 0.0002 to 0.03. This helps to further reduce the release of lattice oxygen and suppress the oxygen reduction reaction at high voltage.

[0008] In some embodiments of this application, the peak intensity of the first characteristic peak is 27 mAh / V to 45 mAh / V, and the peak intensity of the second characteristic peak is 0.01 mAh / V to 3.0 mAh / V; optionally, the peak intensity of the first characteristic peak is 32 mAh / V to 45 mAh / V, and the peak intensity of the second characteristic peak is 0.01 mAh / V to 1.0 mAh / V. This helps to reduce the release of lattice oxygen and suppress the oxygen reduction reaction at high voltages.

[0009] In some embodiments of this application, during the first discharge cycle, the differential capacity curve of the coin cell exhibits a third characteristic peak between 2.5V and 2.7V, with a peak intensity of 0.01mAh / V to 0.3mAh / V; optionally, the peak intensity of the third characteristic peak is 0.01mAh / V to 0.2mAh / V. Therefore, the lithium replenishment agent has a low reversible capacity during discharge, resulting in a better lithium replenishment effect and improving the effective utilization rate of lithium ions.

[0010] In some embodiments of this application, the XRD pattern of the lithium replenishing agent exhibits a first diffraction peak at 2θ of 22.5°–24.0° and a second diffraction peak at 2θ of 32.5°–34.0°, with the ratio of the peak intensity of the first diffraction peak to that of the second diffraction peak being 1.5–1.9; optionally, the ratio is 1.5–1.7. This lower peak intensity ratio is beneficial for weakening the Co-dominated tetrahedral ordered environment and mitigating the release of lattice oxygen under high delithiation conditions.

[0011] In some embodiments of this application, the agglomeration index of the lithium replenishing agent is 0.5 to 6. Therefore, the lithium replenishing agent has a moderate degree of particle agglomeration, less surface exposure, is less likely to react with air and moisture, and is conducive to the complete decomposition of the lithium replenishing agent.

[0012] In some embodiments of this application, the particle size D of the lithium supplement is... v50 The primary particle size of the lithium supplement is 1 μm to 30 μm; optionally, 5 μm to 20 μm; and / or, the primary particle size D of the lithium supplement is... 50 The particle size ranges from 0.5 μm to 20 μm; optionally, from 4 μm to 15 μm. This helps to avoid agglomeration and increased side reactions caused by excessively fine particles, as well as uneven dispersion and processing difficulties caused by excessively large particles, thereby improving the processing performance of the cathode slurry.

[0013] In some embodiments of this application, the lithium replenishing agent further includes a coating layer, which at least partially coats the surface of the lithium-rich transition metal oxide. The coating layer includes at least one oxide of the nitrogen element (T); optionally, the coating layer includes at least one of Nb₂O₅, Ta₂O₅, Al₂O₃, ZrO₂, and TiO₂. This effectively inhibits the reaction of the lithium replenishing agent with moisture, carbon dioxide, etc., in the air, thus improving the air stability of the lithium replenishing agent.

[0014] In some embodiments of this application, based on the total mass of the lithium replenishing agent, the mass percentage of the lithium-rich transition metal oxide is 98.0 wt% to 99.5 wt%, and the mass percentage of the coating layer is 0.5 wt% to 2 wt%. This is beneficial for simultaneously achieving both the effective delithiation capacity and air stability of the lithium replenishing agent.

[0015] In some embodiments of this application, the coating layer covers 70% to 90% of the surface of the lithium-rich transition metal oxide. Therefore, the coating layer exhibits good density and stability, which helps to suppress the reaction between the lithium replenishing agent and moisture, carbon dioxide, etc., in the air, thereby improving the storage stability of the lithium replenishing agent.

[0016] In some embodiments of this application, the specific surface area of ​​the lithium replenishing agent is 0.3 m². 2 / g~1.0m 2 / g; optionally, 0.3m 2 / g~0.7m 2 / g. This helps reduce the occurrence of side reactions on the surface of the lithium supplement and improves the processing stability of the cathode slurry.

[0017] In some embodiments of this application, the compaction density of the lithium supplement is 1.5 g / cm³. 3 ~2.5g / cm 3 ; optional, 1.9 g / cm 3 ~2.3g / cm 3 This is beneficial for improving the energy density of lithium-ion batteries.

[0018] In some embodiments of this application, the lithium replenishing agent retains 80% to 99% of its capacity after being placed for 4 hours at a temperature of 25℃±1℃ and a relative humidity of 15%±2%. Therefore, the lithium replenishing agent exhibits high air stability.

[0019] In some embodiments of this application, the total amount of O2 generated per mole of the lithium replenishing agent during the charging process of the coin cell is 0.1 mol to 0.4 mol. This indicates that the lattice oxygen evolution during the charging decomposition process of the lithium replenishing agent is more effectively suppressed, reducing the generation of gaseous byproducts and interfacial side reactions.

[0020] In a second aspect of this application, a method for preparing the aforementioned lithium supplement is proposed, comprising: first mixing a cobalt source, an M source, a Q source, and a first T source to obtain a metal mixture; second mixing the metal mixture with a lithium source to obtain a precursor mixture; subjecting the precursor mixture to a first sintering treatment under an inactive atmosphere to obtain a pre-sintered product; wherein the temperature of the first sintering treatment is 300℃~500℃; and crushing the pre-sintered product and then subjecting it to a second sintering treatment under an inactive atmosphere to obtain the lithium supplement. Thus, this application, by elemental doping of lithium-rich transition metal oxides and controlling sintering conditions, obtains a lithium supplement with high air stability and low gas production. Furthermore, the preparation method is simple, easy to operate, and readily applicable for large-scale industrial production.

[0021] In some embodiments of this application, the first sintering treatment takes 3 to 6 hours; and / or the second sintering treatment takes 500°C to 1000°C for 8 to 24 hours. This is beneficial for obtaining pure-phase lithium supplement materials.

[0022] In some embodiments of this application, the lithium supplement has a D v50 The particle size ranges from 1 μm to 25 μm. This facilitates obtaining lithium supplementers with suitable particle size, thereby improving the dispersibility of the lithium supplementers.

[0023] In some embodiments of this application, the method further includes: after the second sintering treatment, mixing the product with a second T source and performing a third sintering treatment under an inactive atmosphere to form a coating layer to obtain the lithium replenishing agent. This helps to suppress the reaction of the lithium replenishing agent with moisture, carbon dioxide, etc., in the air, further improving the air stability of the lithium replenishing agent.

[0024] In some embodiments of this application, the third sintering treatment is performed at a temperature of 400°C to 800°C for 5 to 10 hours. This helps to form a dense coating layer on the surface of the lithium supplement.

[0025] In some embodiments of this application, the lithium source includes at least one of lithium hydroxide, lithium oxide, and lithium carbonate; and / or, the cobalt source includes at least one of cobalt oxide and cobalt hydroxide; and / or, the M source includes at least one of an oxide or hydroxide corresponding to element M; and / or, the Q source includes at least one of an oxide or hydroxide corresponding to element Q; and / or, the first T source includes at least one of an oxide or hydroxide corresponding to element T; and / or, the second T source includes at least one of an oxide corresponding to element T. Therefore, the raw materials are widely available, the cost is low, and large-scale promotion is convenient.

[0026] In a third aspect, this application proposes a lithium-ion battery comprising a positive electrode, the positive electrode comprising a positive current collector and a positive electrode film layer located on at least one side of the positive current collector, the positive electrode film layer comprising a lithium replenishing agent as described in the first aspect of this application or a lithium replenishing agent prepared using the method described in the second aspect of this application. Thus, the lithium-ion battery has a high initial charge specific capacity. Attached Figure Description

[0027] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, wherein, Figure 1 This is a schematic diagram of the structure of a lithium replenishing agent according to an embodiment of this application; Figure 2 This is a differential capacity curve of a coin cell according to an embodiment of this application; Figure 3 The image shows the XRD pattern of a lithium supplement agent according to one embodiment of this application.

[0028] Explanation of reference numerals in the attached figures: 1-Lithium-rich transition metal oxide, 2-Coating layer. Detailed Implementation

[0029] The embodiments of this application are described in detail below, with examples of these embodiments shown in the accompanying drawings. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0030] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in this application is for the purpose of describing particular embodiments only and is not intended to limit this application; unless otherwise stated, the values ​​of the parameters mentioned in this application can be measured using various measurement methods commonly used in the art (e.g., they can be tested according to the methods given in the embodiments of this application).

[0031] The terms “comprising” and “having”, and any variations thereof, in the specification and claims of this application are open-ended expressions, meaning they include what is specified in this application but do not exclude other aspects.

[0032] In the description of this application, all figures disclosed herein, whether or not the words "approximately" or "about" are used, are approximate values. Each figure may vary by less than 10% or by a difference that is considered reasonable by one of the art, such as 1%, 2%, 3%, 4%, or 5%.

[0033] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for a specific parameter, it is also expected that ranges of 60~110 and 80~120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this application, unless otherwise stated, the numerical range "a~b" 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" indicates that all real numbers between "0~5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0034] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. "First feature" and "second feature" may include one or more of the indicated feature.

[0035] In the description of this application, "A and / or B" can include any of the cases of A alone, B alone, or A and B, where A and B are merely examples and can be any technical feature connected by "and / or" in this application.

[0036] In this application, the order in which the steps are written does not imply a strict execution order and does not limit the implementation process. The specific execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps in this application can be performed sequentially or randomly, preferably sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, if the method may also include step (c), it means that step (c) can 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.

[0037] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0038] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0039] Lithium-rich transition metal oxide Li6CoO4 exhibits some inherent defects in practical applications. For example, this material has poor air stability and is extremely sensitive to humidity in the processing environment, posing a significant challenge to environmental control and quality management in large-scale industrial production. Simultaneously, the material has high residual alkali content, and the delithiation reaction generates gas, which can threaten battery safety. Therefore, developing lithium replenishment agents that are less sensitive to environmental conditions and produce less gas has become a critical issue that urgently needs to be addressed.

[0040] In a first aspect of this application, a lithium supplement agent is proposed, comprising a lithium-rich transition metal oxide, wherein the chemical formula of the lithium-rich transition metal oxide satisfies: Li w Co x M y Q z T u O4, wherein the M element includes at least one of Zn, Mg, Cu, and Ca, the Q element includes at least one of Fe and B, and the T element includes at least one of Nb, Ta, Al, Zr, and Ti; 5.2≤w≤6.12, 0.4≤x≤0.85, 0.05≤y≤0.5, 0.4≤x+y≤0.9, 0.05≤z≤0.55, 0.01≤u≤0.05, x+y+z+u=1; the lithium replenishing agent is assembled into a coin cell, and during the first week of charging, the differential capacity curve of the coin cell has a first characteristic peak between 3.0V and 3.45V, and a second characteristic peak between 3.67V and 4.1V, and the ratio of the peak intensity of the second characteristic peak to the peak intensity of the first characteristic peak is 0.0002~0.11. Therefore, this lithium replenishing agent has high air stability and produces less gas, which can effectively improve the first-week charging specific capacity and safety performance of lithium-ion batteries.

[0041] As an example, w can be 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0 or 6.12, etc. When the molar percentage of lithium is within the aforementioned range, it is beneficial to improve the air stability of the lithium replenishing agent, reduce gas generation during charge-discharge cycles, and at the same time, the specific capacity of the lithium replenishing agent is higher.

[0042] As an example, x can be 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, or 0.85, etc.; y can be 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, or 0.5, etc.; z can be 0.05, 0.15, 0.25, 0.35, 0.45, or 0.55, etc.; u can be 0.01, 0.02, 0.03, 0.04, or 0.05, etc.

[0043] As an example, the ratio of the peak intensity of the second characteristic peak to the peak intensity of the first characteristic peak can be 0.0002, 0.0005, 0.001, 0.005, 0.01, 0.05, 0.08, or 0.11, etc.

[0044] In this application, reference is made to Figure 2 During the first week of charging, the differential capacity curve of the coin cell battery exhibits a first characteristic peak between 3.0V and 3.45V, and a second characteristic peak between 3.67V and 4.1V. The first characteristic peak corresponds to the Co-dominated lithium loss process, where Co... 2+ To Co 4+ The transition, with the second characteristic peak corresponding to the reaction involving charge compensation and lattice oxygen release under high delithiation state. Further XRD results show that the lithium replenisher exhibits a first diffraction peak at 2θ of 22.5°–24.0° and a second diffraction peak at 2θ of 32.5°–34.0°, with the intensity ratio of the first to the second diffraction peak being 1.5–1.9. The decrease in the intensity ratio of the first to the second diffraction peak indicates a weakening of the Co-dominated tetrahedral ordered environment and / or localized order in the lithium replenisher, reducing the proportion of locally highly active Co-O structural units under high delithiation state and weakening the tendency for lattice oxygen to be overactivated. This structural change is further reflected in the electrochemical behavior. Specifically, during the first week of charging, the structural response related to lattice oxygen in the high-voltage delithiation stage is delayed, resulting in a shift of the second characteristic peak towards higher voltage. Simultaneously, the intensity of side reactions in the high-voltage stage weakens, leading to a decrease in the peak intensity of the second characteristic peak. This indicates that the lithium replenisher is less prone to drastic oxygen participation in charge compensation and lattice oxygen release during high-voltage delithiation, which helps suppress gas generation and improve the structural stability of the lithium replenisher.

[0045] In this application, the specific method for preparing a coin cell includes: Lithium supplement, positive electrode conductive agent Super P, and positive electrode binder polyvinylidene fluoride were weighed at a mass ratio of 95:2:3 and added to N-methylpyrrolidone (NMP) to prepare a positive electrode slurry. The solid content of the positive electrode slurry was adjusted to 28%. The mixed positive electrode slurry was then uniformly coated onto aluminum foil with a coating thickness (single-sided) of 100 μm. After drying, the coating was rolled to form the desired electrode. The areal density of the coated electrode was 4 mg / cm³. 2 The positive electrode sheet is dried at 135℃ and then punched into 15mm round sheets. The diaphragm is made of ceramic-modified polyethylene (PE) microporous diaphragm; The negative electrode uses a lithium metal sheet with a diameter of 18mm; The electrolyte consists of ethylene carbonate (EC), ethyl methyl carbonate (DEC), and LiPF6, with the volume ratio of ethylene carbonate (EC) to ethyl methyl carbonate (DEC) being 3:7 and the concentration of LiPF6 being 1 mol / L.

[0046] The positive electrode, separator, negative electrode, electrolyte, battery casing and other accessories are moved into the glove box, and the battery is assembled in the order of stacking from bottom to top and injected with electrolyte. It is then sealed on the packaging machine to obtain a button cell.

[0047] As an example, the differential capacity curve of a coin cell can be obtained by performing the following test on the aforementioned coin cell: The assembled button cell was heated at 25°C with a current of 25 mA g. -1 The current density was used for charge-discharge cycles, with an electrochemical window of 2.0V to 4.5V. The dQ / dV differential capacity curve was obtained from the charge-discharge curve of the first cycle.

[0048] Specifically, the equipment is a Xinwei test cabinet, model: CT4008Tn-5V20mA-HWX, and the test steps are: 1) 25mA g -1 1) Constant current charging to 4.5V; 2) 25mA g -1 3) Discharge at constant current to 2.0V; 4) Stop.

[0049] In some embodiments of this application, the lithium replenishment agent is assembled into a coin cell. During the first week of charging, the differential capacity curve of the coin cell exhibits a second characteristic peak between 3.75V and 4.1V. Therefore, the rightward shift of the second characteristic peak indicates that the high-pressure oxygen reduction reaction is delayed, which helps to further reduce the tendency for lattice oxygen release.

[0050] In some embodiments of this application, the ratio of the peak intensity of the second characteristic peak to the peak intensity of the first characteristic peak is 0.0002 to 0.03. This ratio effectively reflects the proportion of lattice oxygen released. Therefore, it helps to further reduce the release of lattice oxygen and suppress the oxygen reduction reaction at high voltage.

[0051] In some embodiments of this application, the peak intensity of the first characteristic peak is 27 mAh / V to 45 mAh / V (e.g., 27 mAh / V, 30 mAh / V, 35 mAh / V, 40 mAh / V, or 45 mAh / V, etc.), and the peak intensity of the second characteristic peak is 0.01 mAh / V to 3.0 mAh / V (e.g., 0.01 mAh / V, 0.5 mAh / V, 1.0 mAh / V, 2.0 mAh / V, or 3.0 mAh / V, etc.); optionally, the peak intensity of the first characteristic peak is 32 mAh / V to 45 mAh / V, and the peak intensity of the second characteristic peak is 0.01 mAh / V to 1.0 mAh / V. The first characteristic peak represents the Co-dominated lithium loss process, where Co occurs. 2+ To Co 4+ The transition, with the second characteristic peak corresponding to the reaction involving oxygen in charge compensation and lattice oxygen release under high delithiation state, indicates a decrease in the degree of oxygen participation in charge compensation. This stems from the effective suppression of active Co-O units in the lithium supplement structure, reflected in the XRD pattern as a decrease in the ratio of the peak intensities of the first and second diffraction peaks. This helps reduce the release of lattice oxygen and suppress oxygen reduction reactions at high voltages.

[0052] In some embodiments of this application, reference is made to Figure 2 During the first week of discharge, the differential capacity curve of the coin cell exhibits a third characteristic peak between 2.5V and 2.7V. The peak intensity of this third characteristic peak is 0.01mAh / V to 0.3mAh / V (e.g., 0.01mAh / V, 0.05mAh / V, 0.1mAh / V, 0.2mAh / V, or 0.3mAh / V, etc.); optionally, the peak intensity of the third characteristic peak is 0.01mAh / V to 0.2mAh / V. Therefore, the lithium replenishment agent exhibits a low reversible capacity during discharge but a good lithium replenishment effect, which is beneficial for improving the effective utilization rate of lithium ions.

[0053] In some embodiments of this application, reference is made to Figure 3 The XRD pattern of the lithium supplement shows a first diffraction peak at 2θ of 22.5°~24.0°, corresponding to the (101) crystal plane, and a second diffraction peak at 2θ of 32.5°~34.0°, corresponding to the (201) crystal plane.

[0054] In some embodiments of this application, the ratio of the peak intensity of the first diffraction peak to the peak intensity of the second diffraction peak is 1.5 to 1.9, for example, it can be 1.5, 1.6, 1.7, 1.8, or 1.9; optionally, the ratio of the peak intensity of the first diffraction peak to the peak intensity of the second diffraction peak is 1.5 to 1.7. Therefore, this lower peak intensity ratio is beneficial for weakening the tetrahedral ordered environment dominated by Co, and alleviating the release of lattice oxygen under high delithiation state.

[0055] In this application, the XRD pattern testing method is as follows: the sample to be tested is placed in a sample cell, compacted and leveled, and a Rigaku powder X-ray diffractometer (Smartlab 9kW) is used. The target wavelength is Cu (1.5418462Å), tube voltage is 40kV, tube current is 200mA, scanning speed is 10° / min, and scanning range is 10°~90°. A one-dimensional detector (1D) is used for testing. Specific testing conditions are: operating temperature: 21±5℃, humidity: <65%; cooling water circulator: temperature: 23±1℃, water pressure: 0.36MPa; high refrigerant pressure: 0.8MPa~1.8MPa, low refrigerant pressure: 0.4MPa~0.7MPa; step size: 0.0200°.

[0056] In some embodiments of this application, the agglomeration index of the lithium replenishing agent is 0.5 to 6, for example, it can be 0.5, 1, 1.5, 1, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, or 6. Therefore, the lithium replenishing agent has a moderate degree of particle agglomeration, less surface exposure, is less likely to react with air and moisture, and is conducive to the complete decomposition of the lithium replenishing agent.

[0057] In this application, the agglomeration index of the lithium supplement refers to the particle size D of the lithium supplement. v50 With primary particle size D 50 The ratio.

[0058] As an example, the particle size D of the lithium supplement v50 The particle size distribution of the sample was measured using a laser particle size analyzer. The specific test method was as follows: an appropriate amount of the sample to be tested was added to the dry feeding system of the laser particle size analyzer (Mastersizer3000 model). Under the set dispersion pressure and vibration feeding conditions, the sample was uniformly dispersed and passed through the test area for detection. The particle size distribution curve of the sample was recorded.

[0059] As an example, the primary particle size D of the lithium supplement 50The image recognition software used in Metis was employed. The specific testing method was as follows: A scanning electron microscope (SEM) of model ERA-9200 from ELIONIX (Japan) was used to photograph the sample morphology at 1K magnification. The LIBMAS intelligent image analysis system analyzed the SEM images, imported the particle images to be identified, selected a template matching the image scale, and then identified and counted the particles in the image. Contrast analysis was performed on the area of ​​individual particles in the image. A circle with the same area as a single particle was considered an equivalent circle, and the average diameter of these circles was calculated to obtain the average size of the primary particles. For each sample, 10 3K images were identified, and the average size of approximately 500-1000 primary particles was calculated to obtain the particle size D. 50 .

[0060] In some embodiments of this application, the particle size D of the lithium supplement is... v50 The particle size is 1μm to 30μm, for example, it can be 1μm, 5μm, 8μm, 10μm, 15μm, 20μm, 25μm or 30μm, etc.; optionally, 5μm to 20μm; and / or, the primary particle size D of the lithium supplement is... 50 The particle size ranges from 0.5 μm to 20 μm; optionally, from 4 μm to 15 μm. This helps to avoid agglomeration and increased side reactions caused by excessively fine particles, as well as uneven dispersion and processing difficulties caused by excessively large particles, thereby improving the processing performance of the cathode slurry.

[0061] In some embodiments of this application, reference is made to Figure 1 The lithium replenishing agent further includes a coating layer 2, which at least partially coats the surface of the lithium-rich transition metal oxide 1. The coating layer 2 includes at least one oxide of the T element; optionally, the coating layer 2 includes at least one of Nb₂O₅, Ta₂O₅, Al₂O₃, ZrO₂, and TiO₂. These oxides are predominantly composed of strong ionic or covalent bonds, and the coating layer formed from these oxides exhibits good density and stability. Therefore, the coating layer can effectively inhibit the reaction of the lithium replenishing agent with moisture, carbon dioxide, etc., in the air, improving the air stability of the lithium replenishing agent.

[0062] In some embodiments of this application, based on the total mass of the lithium replenishing agent, the mass percentage of the lithium-rich transition metal oxide is 98.0 wt% to 99.5 wt% (e.g., 98.0 wt%, 98.2 wt%, 98.5 wt%, 98.8 wt%, 99.0 wt%, 99.2 wt%, or 99.5 wt%), and the mass percentage of the coating layer is 0.5 wt% to 2 wt% (e.g., 0.5 wt%, 0.8 wt%, 1.0 wt%, 1.2 wt%, 1.5 wt%, 1.8 wt%, or 2 wt%). This is beneficial for simultaneously achieving both the effective delithiation capacity and air stability of the lithium replenishing agent.

[0063] In some embodiments of this application, the coating layer has a coverage of 70% to 90% on the surface of the lithium-rich transition metal oxide, for example, 70%, 75%, 80%, 85%, or 90%. Therefore, the coating layer has good density and stability, which helps to suppress the reaction between the lithium replenishing agent and moisture, carbon dioxide, etc., in the air, thereby improving the storage stability of the lithium replenishing agent.

[0064] In this application, the method for testing the coverage of the coating layer on the lithium-rich transition metal oxide surface is as follows: the sample to be tested is characterized by scanning electron microscopy combined with X-ray energy dispersive spectroscopy to obtain the distribution image of the coating layer elements on the particle surface; multiple fields of view are selected, the area of ​​the region on the outer surface of the particle where the coating layer element signal is detected is statistically analyzed, and its proportion to the total area of ​​the outer surface of the particle is calculated. This proportion is used to characterize the coverage of the coating layer on the lithium-rich transition metal oxide surface.

[0065] In some embodiments of this application, the specific surface area of ​​the lithium replenishing agent is 0.3 m². 2 / g~1.0m 2 / g, for example, can be 0.3m 2 / g, 0.4m 2 / g, 0.5m 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g or 1.0m 2 / g, etc.; optionally, 0.3m 2 / g~0.7m 2 / g. This helps reduce the occurrence of side reactions on the surface of the lithium supplement and improves the processing stability of the cathode slurry.

[0066] In this application, the specific surface area of ​​the lithium supplement was obtained using a Tristar 3020 surface analyzer from Micromeritics. The specific procedure may include: gradually adding N2 to the test material (after which physically adsorbed components have been removed) under vacuum conditions in the testing apparatus; calculating the pressure change caused by N2 adsorption using the constant volume method; and determining the amount of N2 adsorbed according to the gas equation. This yields the amount of N2 adsorbed from 0 atm to 0.3 atm at liquid nitrogen temperature, which is then converted into a specific surface area per unit weight.

[0067] In some embodiments of this application, the compaction density of the lithium supplement is 1.5 g / cm³. 3 ~2.5g / cm 3 For example, it can be 1.5g / cm³. 3 1.7g / cm 3 1.9g / cm 3 2.1g / cm 3 2.3g / cm 3 Or 2.5g / cm 3 etc.; optionally, 1.9 g / cm 3 ~2.3g / cm 3 This is beneficial for improving the energy density of lithium-ion batteries.

[0068] In this application, the method for testing the compaction density of the lithium supplement is as follows: a predetermined mass of the powder to be tested is weighed, added to a mold with a known inner diameter, compacted under a set pressure, and after holding the pressure for a predetermined time, the sample thickness is tested using Powder Loresta software, and a compaction density report is generated.

[0069] In some embodiments of this application, the lithium replenishing agent retains 80% to 99% of its capacity after being left for 4 hours at a temperature of 25℃±1℃ and a relative humidity of 15%±2%. For example, the capacity retention can be 80%, 82%, 85%, 87%, 90%, 92%, 95%, 97%, or 99%. Therefore, the lithium replenishing agent exhibits high air stability.

[0070] In this application, the test method for the capacity retention of the lithium supplement is as follows: (1) Weigh the predetermined mass of the powder to be tested, and prepare a coin cell with a fresh lithium replenishing electrode according to the specific preparation method of the coin cell described above. Incubate the assembled coin cell at 25°C with 25 mA g. -1 The current density was used for charge-discharge cycles, with an electrochemical window of 2.0V~4.5V. The charge specific capacity C1 of the first cycle was obtained from the charge-discharge curve of the first cycle. (2) Weigh the predetermined mass of the powder to be tested, place it in air with a relative humidity of 15%±2% for 4 hours, and then take it out. Prepare a coin cell with an air-exposed lithium replenishment electrode according to the specific preparation method of the coin cell described above. Place the assembled coin cell at 25°C with a concentration of 25 mA g. -1 The current density was used for charge-discharge cycles, with an electrochemical window of 2.0V~4.5V. The first-cycle charge specific capacity C2 was obtained from the charge-discharge curve of the first cycle. (3) The capacity retention rate of the lithium supplement to be tested is C2 / C1.

[0071] In some embodiments of this application, the total amount of O2 generated per mole of the lithium replenishing agent during the charging process of the coin cell is 0.1 mol to 0.4 mol, for example, 0.1 mol, 0.2 mol, 0.3 mol, or 0.4 mol. This indicates that the lattice oxygen evolution during the charging decomposition process of the lithium replenishing agent is more effectively suppressed, reducing the generation of gaseous byproducts and interfacial side reactions.

[0072] In this application, the total amount of O2 generated per mole of lithium replenisher during the decomposition of the coin cell charging process was measured by differential electrochemical mass spectrometry.

[0073] In a second aspect, this application proposes a method for preparing the aforementioned lithium replenishing agent. This application obtains a lithium replenishing agent with high air stability and low gas production by elemental doping of lithium-rich transition metal oxides and controlling sintering conditions. Furthermore, the preparation method is simple, easy to operate, and readily applicable for large-scale industrial production. Specifically, the method includes: S1: The cobalt source, M source, Q source and the first T source are mixed to obtain a metal mixture.

[0074] In some embodiments of this application, the cobalt source includes at least one of cobalt oxide and cobalt hydroxide; the M source includes at least one of an oxide or hydroxide corresponding to element M; the Q source includes at least one of an oxide or hydroxide corresponding to element Q; and the first T source includes at least one of an oxide or hydroxide corresponding to element T. Therefore, the raw materials are widely available, the cost is low, and large-scale promotion is convenient.

[0075] S2: The metal mixture is mixed with the lithium source for a second time to obtain a precursor mixture.

[0076] In some embodiments of this application, the lithium source includes at least one of lithium hydroxide, lithium oxide, and lithium carbonate.

[0077] S3: The precursor mixture is subjected to a first sintering treatment under an inactive atmosphere to obtain a pre-sintered product.

[0078] In some embodiments of this application, the temperature of the first sintering treatment is 300℃~500℃, for example, it can be 300℃, 350℃, 400℃, 450℃ or 500℃, etc.; the time of the first sintering treatment is 3h~6h, for example, it can be 3h, 4h, 5h or 6h, etc.

[0079] Furthermore, the inactive atmosphere is nitrogen or argon, and the equipment used for the first sintering process can be a tube furnace, a box furnace, a pusher kiln, or a roller kiln, etc.

[0080] S4: After crushing the pre-calcined product, a second sintering treatment is performed under an inactive atmosphere to obtain the lithium supplement.

[0081] In some embodiments of this application, the temperature of the second sintering treatment is 500℃~1000℃ (e.g., 500℃, 600℃, 700℃, 800℃, 900℃, or 1000℃), and the time is 8h~24h (e.g., 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, or 24h). This is beneficial for obtaining pure-phase lithium supplement materials.

[0082] In some embodiments of this application, the lithium supplement has a D v50 The particle size can range from 1 μm to 25 μm, for example, it can be 1 μm, 5 μm, 8 μm, 10 μm, 15 μm, 20 μm, or 25 μm. This is beneficial for obtaining lithium supplementers with suitable particle size, thereby improving the dispersibility of the lithium supplementers.

[0083] As an example, the pre-calcined product is crushed, sieved, and then subjected to a second sintering treatment under an inactive atmosphere to obtain a lithium supplement.

[0084] Furthermore, the inactive atmosphere is nitrogen or argon, and the equipment used for the second sintering process can be a tube furnace, box furnace, pusher kiln, or roller kiln, etc.

[0085] Furthermore, the crushing method includes at least one of ball milling, sand milling, air jet milling, and colloid milling.

[0086] Furthermore, sieving is performed using a 200-400 mesh sieve.

[0087] In some embodiments of this application, the method further includes: after the second sintering treatment, mixing the product with a second T source and performing a third sintering treatment under an inactive atmosphere to form a coating layer to obtain the lithium replenishing agent. This helps to suppress the reaction of the lithium replenishing agent with moisture, carbon dioxide, etc., in the air, further improving the air stability of the lithium replenishing agent.

[0088] In some embodiments of this application, the second T source includes at least one oxide corresponding to the T element. Therefore, the raw materials are widely available, the cost is low, and large-scale promotion is easy.

[0089] In some embodiments of this application, the temperature of the third sintering treatment is 400°C to 800°C (e.g., 400°C, 500°C, 600°C, 700°C, or 800°C), and the time is 5h to 10h (e.g., 5h, 6h, 7h, 8h, 9h, or 10h). This helps to form a dense coating layer on the surface of the lithium supplement.

[0090] In a third aspect, this application proposes a lithium-ion battery comprising a positive electrode, the positive electrode comprising a positive current collector and a positive electrode film layer located on at least one side of the positive current collector, the positive electrode film layer comprising a lithium replenishing agent as described in the first aspect of this application or a lithium replenishing agent prepared using the method described in the second aspect of this application. Thus, the lithium-ion battery has a high initial charge specific capacity.

[0091] In some embodiments of this application, the aforementioned lithium supplement can be directly used as the positive electrode active material.

[0092] In some embodiments of this application, the positive electrode film layer further includes a positive electrode active material, which includes at least one of lithium iron phosphate, lithium manganese phosphate, lithium iron manganese phosphate, lithium cobalt phosphate, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium nickel manganese oxide, and lithium-rich layered oxides. The lithium replenishing agent of this application can be compounded with the aforementioned positive electrode active materials, thereby effectively improving the energy density and cycle life of lithium-ion batteries.

[0093] The description of the various embodiments above tends to emphasize the differences between the various embodiments. The similarities or similarities between them can be referred to, and for the sake of brevity, they will not be repeated here.

[0094] The following specific embodiments illustrate the solution of this application. It should be noted that these embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0095] Example 1 (1) Weigh CoO, ZnO, Al2O3 and Fe2O3 in a ratio of 0.5:0.2:0.015:0.135, mix them evenly to obtain a metal mixture; (2) A certain amount of Li2O is added to the metal mixture (the ratio of Li2O, CoO, ZnO, Al2O3 and Fe2O3 is 2.85:0.5:0.2:0.015:0.135), and after mixing evenly, a precursor mixture is obtained; (3) The precursor mixture was subjected to a first sintering treatment under a nitrogen atmosphere. The temperature of the first sintering treatment was 450°C and the time was 4h to obtain the pre-sintered product. (4) The pre-calcined product was crushed by air jet milling and sieved through a 400-mesh sieve. Then, a second sintering treatment was carried out under a nitrogen atmosphere at a temperature of 750°C for 12 hours to obtain the product with the chemical formula Li. 5.7 Co 0.5 Zn 0.2 Al 0.03 Fe 0.27 Lithium-rich transition metal oxides of O4; (5) Weigh the aforementioned lithium-rich transition metal oxide and ZrO2 at a molar ratio of 1:0.02, mix them, and then perform a third sintering treatment under a nitrogen atmosphere. The temperature of the third sintering treatment is 500℃ and the time is 8h. The above sample was crushed by an air jet mill and sieved through a 400-mesh sieve to obtain the chemical formula Li. 5.7 Co 0.5 Zn 0.2 Al 0.03 Fe 0.27 Lithium supplementer of O4·0.02ZrO2.

[0096] The differences between other embodiments and comparative examples and embodiment 1 are shown in Tables 1-1, 1-2 and 1-3.

[0097] Table 1-1

[0098] Table 1-2

[0099] Table 1-3

[0100] In this context, " / " indicates that the step was not performed or the substance was not added.

[0101] The lithium supplement prepared above was subjected to the aforementioned tests, and the test results are shown in Table 2.

[0102] Table 2

[0103] Battery assembly: Lithium supplement, positive electrode conductive agent Super P, and positive electrode binder polyvinylidene fluoride were weighed at a mass ratio of 95:2:3 and added to N-methylpyrrolidone (NMP) to prepare a positive electrode slurry. The solid content of the positive electrode slurry was adjusted to 28%. The mixed positive electrode slurry was then uniformly coated onto aluminum foil with a coating thickness (single-sided) of 100 μm. After drying, the coating was rolled to form the desired electrode. The areal density of the coated electrode was 4 mg / cm³. 2 The positive electrode sheet is dried at 135℃ and then punched into 15mm round sheets. The diaphragm is made of ceramic-modified polyethylene (PE) microporous diaphragm; The negative electrode uses a lithium metal sheet with a diameter of 18mm; The electrolyte consists of ethylene carbonate (EC), ethyl methyl carbonate (DEC), and LiPF6, with the volume ratio of ethylene carbonate (EC) to ethyl methyl carbonate (DEC) being 3:7 and the concentration of LiPF6 being 1 mol / L.

[0104] The positive electrode, separator, negative electrode, electrolyte, battery casing and other accessories are moved into the glove box, and the battery is assembled in the order of stacking from bottom to top and injected with electrolyte. It is then sealed on the packaging machine to obtain a button cell.

[0105] The aforementioned button cells were subjected to the tests described above and the following tests. The test results are shown in Tables 3-1 and 3-2.

[0106] (1) First week charge specific capacity: The assembled coin cell was charged and discharged at 25°C with a current density of 25 mA / g, where the electrochemical window was 2.0V~4.5V, and the first week charge specific capacity was read from the test software.

[0107] (2) Gas production: The gas production of lithium supplement I gas The total amount of O2 produced per mole of lithium replenisher during the decomposition process is measured by differential electrochemical mass spectrometry.

[0108] (3) Capacity retention: Weigh the predetermined mass of the powder to be tested, and prepare a coin cell with a fresh lithium replenishing electrode according to the specific preparation method of the coin cell described above. Incubate the assembled coin cell at 25°C with a capacity of 25 mA g. -1 The current density was used for charge-discharge cycles, with an electrochemical window of 2.0V~4.5V. The charge specific capacity C1 of the first cycle was obtained from the charge-discharge curve of the first cycle. Weigh a predetermined amount of the test powder, place it in air with a relative humidity of 15%±2% for 4 hours, then remove it. Prepare a coin cell with an air-exposed lithium replenishment electrode according to the specific preparation method of the coin cell described above. Incubate the assembled coin cell at 25°C with a 25 mA g-pressure.-1 The current density was used for charge-discharge cycles, with an electrochemical window of 2.0V~4.5V. The first-cycle charge specific capacity C2 was obtained from the charge-discharge curve of the first cycle. The capacity retention of the lithium supplement under test is C2 / C1.

[0109] (4) First-week coulombic efficiency: The assembled coin cells were subjected to 25°C at 25 mA g. -1 The current density was used for charge-discharge cycles, with an electrochemical window of 2.0V~4.5V. The first-cycle charge specific capacity and the first-cycle discharge specific capacity were read from the test software. The ratio of the first-cycle discharge specific capacity to the first-cycle charge specific capacity is the first-cycle coulombic efficiency.

[0110] Table 3-1

[0111] Table 3-2

[0112] As can be seen from Tables 3-1 and 3-2, the coin cells assembled with the lithium replenishing agent prepared in the embodiments of this application exhibit a first characteristic peak between 3.0V and 3.45V and a second characteristic peak between 3.67V and 4.1V during the first week of charging. Furthermore, the ratio of the peak intensity of the second characteristic peak to that of the first characteristic peak is within the range of 0.0002 to 0.11. This indicates that the lithium replenishing agent prepared in this application is less prone to drastic oxygen participation in charge compensation and lattice oxygen release during high-voltage delithiation, which helps suppress gas generation and improve the structural stability of the lithium replenishing agent, effectively increasing the specific capacity of the lithium-ion battery during the first week of charging.

[0113] In Comparative Example 1, the lithium-rich transition metal oxide was not coated and no elemental doping was performed during the preparation of the lithium replenishment agent. As a result, during the first week of charging of the coin cell, the peak position of the second characteristic peak in the differential capacity curve shifted to the left, the peak intensity increased, and the ratio of the peak intensity of the second characteristic peak to the peak intensity of the first characteristic peak increased. This led to the intensification of side reactions, the increase in gas production, the decrease in capacity retention, and the deterioration of air stability.

[0114] Comparative Example 2 did not dop with element M during the preparation of the lithium replenishment agent, which could not effectively regulate the electronic state of oxygen and enhance the stability of lattice oxygen. As a result, during the first charging cycle of the coin cell, the peak position of the second characteristic peak in the differential capacity curve shifted to the left, the peak intensity increased, and the ratio of the peak intensity of the second characteristic peak to the peak intensity of the first characteristic peak increased, leading to enhanced side reactions, increased gas production, reduced capacity retention, and worsened air stability.

[0115] Comparative Example 3 did not dop with T element when preparing the lithium replenishment agent, which could not effectively pin oxygen ions and suppress structural distortion. As a result, during the first week of charging of the coin cell, the peak position of the second characteristic peak in the differential capacity curve shifted to the left, the peak intensity increased, and the ratio of the peak intensity of the second characteristic peak to the peak intensity of the first characteristic peak increased, which led to the enhancement of side reactions, increased gas production, reduced capacity retention, and worsened air stability.

[0116] Comparative Example 4 did not dop with Q element when preparing the lithium replenishment agent, which could not effectively regulate the electronic state of oxygen and enhance the stability of lattice oxygen. As a result, during the first charging cycle of the coin cell, the peak position of the second characteristic peak in the differential capacity curve shifted to the left, the peak intensity increased, and the ratio of the peak intensity of the second characteristic peak to the peak intensity of the first characteristic peak increased, leading to enhanced side reactions, increased gas production, reduced capacity retention, and worsened air stability.

[0117] In Comparative Example 5, the lithium-rich transition metal oxide was not coated during the preparation of the lithium replenishment agent. As a result, during the first week of charging of the coin cell, the peak position of the second characteristic peak in the differential capacity curve shifted to the left, the peak intensity increased, and the ratio of the peak intensity of the second characteristic peak to the peak intensity of the first characteristic peak increased. This led to enhanced side reactions, increased gas production, reduced capacity retention, and worsened air stability.

[0118] Comparative Example 6 did not undergo the first sintering treatment during the preparation of the lithium replenishing agent, and the second sintering temperature was low and the time was short. As a result, during the first week of charging of the coin cell, the peak position of the second characteristic peak in the differential capacity curve shifted to the left, the peak intensity increased, and the ratio of the peak intensity of the second characteristic peak to the peak intensity of the first characteristic peak increased. This led to the intensification of side reactions, the increase in gas production, the decrease in capacity retention, and the deterioration of air stability.

[0119] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A lithium supplement, characterized in that, Li1-xMxO2, wherein M includes at least one of Zn, Mg, Cu, Ca, and x satisfies 0 < x < 0.

2. w Co x M y Q z T u O4, wherein M includes at least one of Zn, Mg, Cu, Ca, Q includes at least one of Fe, B, and T includes at least one of Nb, Ta, Al, Zr, and Ti; 5.2 ≤ w ≤ 6.12, 0.4 ≤ x ≤ 0.85, 0.05 ≤ y ≤ 0.5, 0.4 ≤ x+y ≤ 0.9, 0.05 ≤ z ≤ 0.55, 0.01 ≤ u ≤ 0.05, and x+y+z+u = 1. The lithium replenishing agent is assembled into a coin cell. During the first week of charging, the differential capacity curve of the coin cell has a first characteristic peak between 3.0V and 3.45V, and a second characteristic peak between 3.67V and 4.1V. The ratio of the peak intensity of the second characteristic peak to the peak intensity of the first characteristic peak is 0.0002 to 0.

11.

2. The lithium supplement of claim 1, wherein, The lithium replenishing agent is assembled into a coin cell, and during the first week of charging, the differential capacity curve of the coin cell has a second characteristic peak between 3.75V and 4.1V.

3. The lithium supplement according to claim 1 or 2, characterized in that The ratio of the peak intensity of the second characteristic peak to the peak intensity of the first characteristic peak is 0.0002~0.

03.

4. The lithium supplement agent according to claim 1 or 2, characterized in that, The peak intensity of the first characteristic peak is 27 mAh / V to 45 mAh / V, and the peak intensity of the second characteristic peak is 0.01 mAh / V to 3.0 mAh / V; Optionally, the peak intensity of the first characteristic peak is 32 mAh / V to 45 mAh / V, and the peak intensity of the second characteristic peak is 0.01 mAh / V to 1.0 mAh / V.

5. The lithium supplement agent according to claim 1, characterized in that, During the first discharge cycle, the differential capacity curve of the coin cell battery exhibits a third characteristic peak between 2.5V and 2.7V, with a peak intensity of 0.01mAh / V to 0.3mAh / V. Optionally, the peak intensity of the third characteristic peak is 0.01 mAh / V to 0.2 mAh / V.

6. The lithium supplement agent according to claim 1 or 2, characterized in that, The XRD pattern of the lithium supplement shows a first diffraction peak at 2θ of 22.5°~24.0° and a second diffraction peak at 2θ of 32.5°~34.0°. The ratio of the peak intensity of the first diffraction peak to the peak intensity of the second diffraction peak is 1.5~1.

9. Optionally, the ratio of the peak intensity of the first diffraction peak to the peak intensity of the second diffraction peak is 1.5 to 1.

7.

7. The lithium supplement agent according to claim 1 or 2, characterized in that, The aggregation index of the lithium supplement is 0.5 to 6.

8. The lithium supplement agent according to claim 7, characterized in that, The particle size D of the lithium supplement v50 The thickness is 1 μm to 30 μm; optionally, 5 μm to 20 μm; and / or, The primary particle size D of the lithium supplement is... 50 The range is 0.5μm to 20μm; optionally, it is 4μm to 15μm.

9. The lithium supplement agent according to claim 1 or 2, characterized in that, The lithium replenishing agent further includes a coating layer, which at least partially coats the surface of the lithium-rich transition metal oxide, and the coating layer includes at least one of the oxides of the T element; Optionally, the coating layer includes at least one of Nb2O5, Ta2O5, Al2O3, ZrO2, and TiO2.

10. The lithium supplement agent according to claim 9, characterized in that, Based on the total mass of the lithium replenishing agent, the mass percentage of the lithium-rich transition metal oxide is 98.0 wt% to 99.5 wt%, and the mass percentage of the coating layer is 0.5 wt% to 2 wt%.

11. The lithium supplement agent according to claim 9, characterized in that, The coating layer has a coverage of 70% to 90% on the surface of the lithium-rich transition metal oxide.

12. The lithium supplement agent according to claim 1 or 2, characterized in that, the specific surface area of the lithium supplement is 0.3 m 2 / g ~ 1.0 m 2 / g; optionally, 0.3 m 2 / g ~ 0.7 m 2 / g; and / or, The compaction density of the lithium supplement is 1.5 g / cm 3 2.5 g / cm 3 ; optionally, 1.9 g / cm 3 2.3 g / cm 3 .

13. A method for preparing the lithium supplement agent according to any one of claims 1 to 12, characterized in that, include: The cobalt source, M source, Q source and the first T source are mixed in the first mixture to obtain a metal mixture. The metal mixture is mixed with a lithium source in a second process to obtain a precursor mixture. The precursor mixture is subjected to a first sintering treatment under an inactive atmosphere to obtain a pre-sintered product; wherein the temperature of the first sintering treatment is 300℃~500℃. The pre-calcined product is crushed and then subjected to a second sintering treatment under an inactive atmosphere to obtain the lithium supplement.

14. The method according to claim 13, characterized in that, The first sintering treatment takes 3 to 6 hours; and / or, The second sintering treatment is performed at a temperature of 500℃~1000℃ for 8h~24h.

15. The method according to claim 13 or 14, characterized in that, The D of the lithium supplementing agent is 1 μm to 25 μm. v50 1 μm to 25 μm.

16. The method according to claim 13 or 14, characterized in that, Also includes: After the second sintering treatment, the product is mixed with a second T source and subjected to a third sintering treatment under an inactive atmosphere to form a coating layer to obtain the lithium supplement.

17. The method according to claim 16, characterized in that, The third sintering treatment is performed at a temperature of 400℃ to 800℃ for 5 hours to 10 hours.

18. The method according to claim 16, characterized in that, The lithium source includes at least one of lithium hydroxide, lithium oxide, and lithium carbonate; and / or, The cobalt source includes at least one of cobalt oxide and cobalt hydroxide; and / or, The M source includes at least one of the oxides and hydroxides corresponding to the M element; and / or, The Q source includes at least one of the oxides and hydroxides corresponding to the Q element; and / or, The first T source includes at least one of the oxides and hydroxides corresponding to the element T; and / or, The second T source includes at least one of the oxides corresponding to the T element.

19. A lithium-ion battery, characterized in that, The invention includes a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive electrode film layer located on at least one side of the positive current collector, the positive electrode film layer comprising a lithium replenishing agent as described in any one of claims 1 to 12 or a lithium replenishing agent prepared by the method described in any one of claims 13 to 18.

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