Positive electrode lithium replenishing agent and its preparation method, positive electrode sheet and lithium-ion battery

Abstract

The present application relates to a positive electrode lithium supplement and a preparation method thereof, a positive electrode sheet and a lithium ion battery. The positive electrode lithium supplement comprises a core and a coating layer covering the core; the core comprises a modified lithium-rich nickel oxide, expressed as: Li2Ni 1‑x‑y A x B y M z O 2‑z ; Among them, 0

Description

Technical Field

[0001] The present application relates to the technical field of lithium-ion batteries, and in particular to a positive electrode lithium supplement and a preparation method thereof, a positive electrode sheet and a lithium-ion battery. Background Art

[0002] Lithium-ion batteries are widely used in portable electronic devices, electric vehicles and energy storage systems due to their high energy density, long cycle life and good rate performance. How to further improve the energy density and cycle life of lithium-ion batteries has also become a research hotspot in the field of lithium-ion batteries. Lithium loss is the direct cause of battery degradation. During the first charge and discharge process of the battery, part of the active lithium will react with the electrolyte at the solid-liquid interface of the negative electrode to form a solid electrolyte interface (SEI) film, and permanently consume a large amount of active lithium, thereby reducing the first coulomb efficiency of the battery and causing the battery capacity and energy density to decay. For example, when using a graphite negative electrode, about 10% of the active lithium source will be consumed in the first cycle, and when Si, SiO, etc. are used as the negative electrode, more active lithium will be consumed.

[0003] At present, pre-lithiation technology, also known as lithium replenishment technology, is to add lithium replenisher to the battery before the battery works to replenish lithium ions, thereby offsetting the permanent consumption of active lithium in the battery to improve the reversible energy density of the battery. Pre-lithiation technology includes negative electrode lithium replenishment and positive electrode lithium replenishment. Compared with the difficult and high-investment negative electrode lithium replenishment technology, the positive electrode lithium replenishment process is simple, low-cost and safe, and can be combined with traditional battery production processes, with broad industrial application prospects.

[0004] Although positive electrode lithium replenishment, that is, adding a small amount of positive electrode lithium replenisher during the slurrying process of the positive electrode material, is an effective strategy to compensate for the loss of active lithium, the traditional positive electrode lithium replenisher has serious gas production side reactions, high surface residual alkali content and poor air stability, which has an adverse effect on the electrochemical performance of the battery. Summary of the invention

[0005] Based on this, it is necessary to provide a positive electrode lithium replenisher and its preparation method, a positive electrode sheet and a lithium ion battery to solve the problems of serious gas production side reaction, high surface residual alkali content and poor air stability of traditional positive electrode lithium replenishers.

[0006] In the first aspect of the present application, a positive electrode lithium supplement is provided, comprising a core and a coating layer covering the core; the core comprises a modified lithium-rich nickel oxide, and the expression is: Li2Ni 1-x-y A x B y M z O2;

[0007] Among them, 0 <x≤0.1,0<y≤0.1,0<z≤0.1;

[0008] The A element and the B element each independently include at least one of La, Ce, Ta, W, Zr, Ti, Sr, Sn, Sb, Nb, Mo, Y and Al, and the A element and the B element are different;

[0009] M elements include C;

[0010] The coating layer includes lithium oxide and carbide;

[0011] The lithium oxide and the carbide each independently contain the A element and the B element;

[0012] The carbide has oxygen vacancies.

[0013] In one embodiment, the M element further includes F;

[0014] The coating layer further includes fluoride, and the fluoride contains the A element and the B element.

[0015] In one embodiment, the A element includes at least one of Ce, Ta, Ti, Sr, Sn, Sb and Al, and the B element includes at least one of La, W, B, Zr, Mo, Y and Nb.

[0016] In one embodiment, the coating layer has a thickness of 1 nm to 25 nm.

[0017] In one embodiment, the coating layer accounts for 0.1% to 3% by mass in the positive electrode lithium supplement.

[0018] In one embodiment, the median particle size of the positive electrode lithium supplement is 5 μm to 10 μm.

[0019] In a second aspect of the present application, a method for preparing the positive electrode lithium supplement as described above is provided, comprising the following steps:

[0020] Mixing lithium-rich nickel oxide, reducing organic matter and coating material to prepare a second powder;

[0021] calcining the second powder under an inert atmosphere to prepare the positive electrode lithium supplement;

[0022] Wherein, the coating material includes source A and source B, and the source A and / or the source B include metal organic matter.

[0023] In one embodiment, the reducing organic matter includes at least one of urea, glycine and citric acid.

[0024] In one embodiment, the A source includes at least one of the oxide, fluoride, hydroxide and ethanolate of the A element.

[0025] In one embodiment, the B source includes at least one of an oxide, a fluoride, a hydroxide and an ethoxide of the B element.

[0026] In one embodiment, the reducing organic matter includes urea.

[0027] In one embodiment, the A source includes at least one of tantalum oxide, titanium oxide and cerium fluoride.

[0028] In one embodiment, the B source includes niobium ethoxide.

[0029] In one embodiment, in the second powder, the mass ratio of the lithium-rich nickel oxide, the reducing organic matter, the source A and the source B is 100: (0.1~0.8): (0.01~5): (0.01~5).

[0030] In one embodiment, the method of mixing the lithium-rich nickel oxide, the reducing organic matter and the coating material comprises ball milling.

[0031] In one embodiment, the inert atmosphere of the calcination process includes at least one of nitrogen, helium, neon, argon, krypton and xenon.

[0032] In one embodiment, the calcination temperature of the calcination treatment is 500°C to 800°C.

[0033] In one embodiment, the calcination time of the calcination treatment is 5h~10h.

[0034] In one embodiment, the method for preparing the lithium-rich lithium nickelate comprises the following steps:

[0035] Mixing a lithium source and a nickel source to prepare a first powder;

[0036] The first powder is sintered in an inert atmosphere to prepare the lithium-rich lithium nickel oxide.

[0037] In one embodiment, the lithium source includes at least one of lithium oxide, lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate and lithium oxalate.

[0038] In one embodiment, the nickel source includes at least one of nickel oxide, nickel hydroxide, nickel nitrate, nickel chloride and nickel sulfate.

[0039] In one embodiment, the BET specific surface area of ​​the lithium source and the nickel source is independently 5 m 2 / g~10m 2 / g.

[0040] In one embodiment, the median particle size of the lithium source and the nickel source is independently 1 μm to 3 μm.

[0041] In one embodiment, the molar ratio of the lithium element in the lithium source to the nickel element in the nickel source is (1.8~2.0):1.

[0042] In one embodiment, the method of mixing the lithium source and the nickel source comprises ball milling.

[0043] In one embodiment, the inert atmosphere of the sintering process includes at least one of nitrogen, helium, neon, argon, krypton and xenon.

[0044] In one of the embodiments, the sintering temperature of the sintering process is 700°C~800°C.

[0045] In one embodiment, the sintering time of the sintering treatment is 15h~20h.

[0046] In one embodiment, the heating rate of the sintering process is 0.5°C / min~3°C / min.

[0047] In a third aspect of the present application, there is provided a positive electrode sheet, comprising a positive electrode current collector and a positive electrode active layer covering the positive electrode current collector;

[0048] The positive electrode active layer includes the positive electrode lithium replenisher as described above, or includes the positive electrode lithium replenisher prepared by the preparation method of the positive electrode lithium replenisher as described above.

[0049] In one embodiment, the mass proportion of the positive electrode lithium supplement in the positive electrode active layer is 1% to 10%.

[0050] In a fourth aspect of the present application, a lithium-ion battery is provided, comprising the positive electrode sheet as described above.

[0051] This application has at least the following beneficial effects:

[0052] This application uses modified lithium-rich nickel-acid lithium as the core, and uses lithium oxide and carbide to form a coating layer on the surface of the core. The A and B elements in the core and the coating layer will generate lithium oxide with the active lithium, reduce the free lithium content on the surface, and reduce the gas production side reaction between the positive electrode lithium supplement and the electrolyte during the charge and discharge cycle. At the same time, it is also beneficial to reduce the residual alkali content on the surface, avoid the problem of poor gelation during the pulping process, and improve the processing performance. Providing a coating layer on the surface of the core can effectively prevent moisture in the air from having side reactions on the surface and improve the air stability of the positive electrode lithium supplement; at the same time, the A and B elements in the coating layer form amorphous carbides with carbon atoms, which have certain oxygen vacancies and can adsorb lattice oxygen to inhibit the escape of lattice oxygen from the positive electrode lithium supplement, thereby achieving the purpose of inhibiting gas production.

[0053] In addition, the binding energy of element A and element B with oxygen is higher than that of nickel and oxygen, which can jointly inhibit the precipitation of lattice oxygen. The co-doping of element A and element B can effectively improve the valence state of some elements in the material to improve the stability of the material structure and the conductivity of the material surface, provide lithium ion migration channels, and reduce the occurrence of electrolyte side reactions, thereby achieving the effect of reducing gas production. Compared with single metal element doping, bimetallic element doping can play a synergistic role, which can greatly reduce the residual alkali on the surface of the positive electrode lithium supplement, effectively reduce the occurrence of side reactions between the positive electrode lithium supplement and the electrolyte, and also can form a more complete and stable carbide coating network, thereby effectively inhibiting the release of lattice oxygen. Therefore, the positive electrode lithium supplement of the present application has the advantages of good air stability, low surface residual alkali content and low gas production during the cycle, which is beneficial to improve the electrochemical properties of lithium-ion batteries such as safety, cycle stability and battery capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] In order to more clearly illustrate the technical solutions in the embodiments of the present application and to more completely understand the present application and its beneficial effects, the following is a brief introduction to the drawings required for the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present application, and those skilled in the art can obtain other drawings based on these drawings without creative work.

[0055] Figure 1 Element distribution diagram of the positive electrode lithium supplement agent of Example 1;

[0056] Figure 2 This is the Raman spectrum of the positive electrode lithium supplement agent of Example 1;

[0057] Figure 3 This is a SEM image of the positive electrode lithium supplement agent of Example 1;

[0058] Figure 4 This is a SEM image of the positive electrode lithium supplement agent of Example 2;

[0059] Figure 5 This is a SEM image of the positive electrode lithium supplement agent of Example 3;

[0060] Figure 6 This is the SEM image of the positive electrode lithium supplement agent of Example 4. DETAILED DESCRIPTION

[0061] In order to facilitate the understanding of the present application, the present application is further described in detail below in conjunction with specific embodiments. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present application more thorough and comprehensive.

[0062] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0063] In the present application, the meaning of "and / or" includes any and all combinations of one or more related listed items. "At least one" means more than one, such as one, two and more than two. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layer" means at least two layers, such as two layers, three layers, etc., unless otherwise clearly and specifically defined. In the description of the present application, "several" means at least one, such as one, two, etc., unless otherwise clearly and specifically defined.

[0064] When a numerical range is disclosed in this application, the above range is considered to be continuous and includes the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed in this application should be understood to include any and all subranges included therein.

[0065] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0066] In this application, "above" or "below" includes the number itself. For example, "1 below" includes 1.

[0067] The temperature parameters in this application, unless otherwise specified, are allowed to be either constant temperature treatment or to vary within a certain temperature range. It should be understood that the constant temperature treatment allows the temperature to fluctuate within the accuracy range controlled by the instrument. Fluctuations within the range of ±5°C, ±4°C, ±3°C, ±2°C, and ±1°C are allowed.

[0068] In the present application, room temperature refers to indoor temperature, normal temperature or general temperature. Generally speaking, the range of room temperature can be any one of the following temperature intervals: 23°C ± 2°C, 25°C ± 5°C or 20°C ± 5°C.

[0069] Pre-lithiation technology, also known as lithium replenishment technology, can be divided into two methods: negative electrode lithium replenishment and positive electrode lithium replenishment. Negative electrode lithium replenishment includes lithium foil replenishment, lithium powder replenishment and electrolytic lithium salt replenishment, but there are problems such as the incompatibility of the use of metallic lithium with the production environment and conventional solvents, and the chemical stability of the negative electrode lithium replenisher is poor, posing a major safety hazard. Compared with negative electrode lithium replenishment, the positive electrode lithium replenisher can be made into a positive electrode slurry together with positive electrode active materials and binders, and coated on the surface of the positive electrode current collector to form a positive electrode active layer. It can be combined with traditional battery production processes and has the advantages of high safety, low cost and simple process, thus showing a broader industrial application prospect.

[0070] Most positive electrode lithium supplements use Li2NiO2 (i.e., lithium-rich lithium nickelate). During the first cycle, Li2NiO2 with an orthorhombic phase structure will be irreversibly converted into LiNiO2 with a layered structure (i.e., layered lithium nickelate) and release lithium ions. In the subsequent cycle process, lithium is deintercalated through the LiNiO2 phase. Without any modification, modification or doping, the structure of LiNiO2 is unstable, and it is easy to collapse and decompose into NiO and O2 during the cycle of lithium deintercalation. This phenomenon is the direct cause of the sharp increase in gas production in batteries with positive electrode lithium supplements, and the increase in gas production O2 is proportional to the increase in NiO phase, which in turn has an adverse effect on the safety and cycle stability of the battery.

[0071] At the same time, positive electrode lithium supplements usually have strong alkalinity, and will react with binders such as polyvinylidene fluoride (PVDF) during slurry preparation, resulting in poor chemical gelation of the positive electrode slurry, which reduces the bonding force between the positive electrode active layer and the positive electrode current collector, causing the positive electrode active layer to easily peel off from the surface of the positive electrode current collector. In addition, positive electrode lithium supplements may also react with moisture in the air on the surface, have poor air stability, are difficult to store and transport, and can also cause battery capacity decay.

[0072] Based on this, in the first aspect of the present application, a positive electrode lithium replenisher is provided to solve the problems of serious gas production side reaction, high surface residual alkali content and poor air stability of traditional positive electrode lithium replenishers.

[0073] In some embodiments, the positive electrode lithium supplement includes a core, and a coating layer coating the core;

[0074] The core includes a modified lithium-rich nickel oxide, which is expressed as: Li2Ni 1-x-y A x B y M z O2;

[0075] Among them, 0 <x≤0.1,0<y≤0.1,0<z≤0.1;

[0076] The A element and the B element each independently include at least one of La, Ce, Ta, W, Zr, Ti, Sr, Sn, Sb, Nb, Mo, Y and Al, and the A element and the B element are different;

[0077] M elements include C;

[0078] The coating layer includes lithium oxide and carbide;

[0079] The lithium oxide and carbide each independently contain the A element and the B element;

[0080] Carbides have oxygen vacancies.

[0081] This application uses modified lithium-rich nickel-acid lithium as the core, and uses lithium oxide and carbide to form a coating layer on the surface of the core. The A and B elements in the core and the coating layer will generate lithium oxide with the active lithium, reduce the free lithium content on the surface, and reduce the gas production side reaction between the positive electrode lithium supplement and the electrolyte during the charge and discharge cycle. At the same time, it is also beneficial to reduce the residual alkali content on the surface, avoid the problem of poor gelation during the pulping process, and improve the processing performance. Providing a coating layer on the surface of the core can effectively prevent moisture in the air from having side reactions on the surface and improve the air stability of the positive electrode lithium supplement; at the same time, the A and B elements in the coating layer form amorphous carbides with carbon atoms, which have certain oxygen vacancies and can adsorb lattice oxygen to inhibit the escape of lattice oxygen from the positive electrode lithium supplement, thereby achieving the purpose of inhibiting gas production.

[0082] In addition, the binding energies of element A and element B with oxygen are both higher than that of nickel and oxygen, which can jointly inhibit the precipitation of lattice oxygen. The co-doping of element A and element B can effectively improve the valence states of some elements in the material to enhance the structural stability of the material and the conductivity of the material surface, provide lithium-ion migration channels, and reduce the occurrence of side reactions of the electrolyte, achieving the effect of reducing gas generation. Compared with single-metal element doping, dual-metal element doping can play a synergistic effect, which can greatly reduce the residual alkali on the surface of the cathode lithium supplement agent, effectively reduce the occurrence of side reactions between the cathode lithium supplement agent and the electrolyte, and at the same time can also form a more perfect and stable carbide coating network, thereby effectively inhibiting the release of lattice oxygen. Therefore, the cathode lithium supplement agent of this application has the advantages of good air stability, low surface residual alkali content, and less gas generation during the cycling process, which is beneficial to improving the electrochemical performance such as the safety, cycling stability, and battery capacity of lithium-ion batteries.

[0083] As an example, the value of x can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, and 0.10. Further, it can be optionally 0 < x ≤ 0.01, still further optionally 0 < x ≤ 0.001, and even further optionally 0 < x ≤ 0.0001, such as 0.00001, 0.00002, 0.00003, 0.00004, 0.00005, 0.00006, 0.00007, 0.00008, 0.00009, or 0.0001.

[0084] As an example, the value of y can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, and 0.10. Further, it can be optionally 0 < y ≤ 0.01, still further optionally 0 < y ≤ 0.001, and even further optionally 0 < y ≤ 0.0001, such as 0.00001, 0.00002, 0.00003, 0.00004, 0.00005, 0.00006, 0.00007, 0.00008, 0.00009, or 0.0001.

[0085] As an example, the value of z can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, and 0.10. Further, it can be optionally 0 < z ≤ 0.01, still further optionally 0 < z ≤ 0.001, and even further optionally 0 < z ≤ 0.0001, such as 0.00001, 0.00002, 0.00003, 0.00004, 0.00005, 0.00006, 0.00007, 0.00008, 0.00009, or 0.0001.

[0086] It can be understood that the values ​​of x, y and z can be below 0.0001, indicating that the doping elements of the positive electrode lithium supplement of the present application can promote lithium-ion batteries to achieve better electrochemical performance at extremely low doping levels, with low cost, which is conducive to industrial application.

[0087] As an example, the A element and the B element can be independently selected from any one of La, Ce, Ta, W, Zr, Ti, Sr, Sn, Sb, Nb, Mo, Y and Al, or can be independently selected from a combination of two or more of La, Ce, Ta, W, Zr, Ti, Sr, Sn, Sb, Nb, Mo, Y and Al. At the same time, the A element and the B element are different, that is, the modified lithium-rich nickel oxide is doped with at least two metal elements. For example, if the A element is selected from La, the B element is selected from at least one of Ce, Ta, W, Zr, Ti, Sr, Sn, Sb, Nb, Mo, Y and Al; or, if the A element is selected from Ce and Ti, the B element is selected from at least one of La, Ta, W, Zr, Sr, Sn, Sb, Nb, Mo, Y and Al; and so on.

[0088] As an example, the M element includes C, that is, the M element can be selected from C only, or can be selected from a combination of C and other non-metallic elements. There is no special limitation on the types of non-metallic elements, including but not limited to: F, Cl, Br, S and B.

[0089] As an example, the lithium oxide in the coating layer is selected from at least two of lanthanum lithium oxide, cerium lithium oxide, tantalum lithium oxide, tungsten lithium oxide, zirconium lithium oxide, titanium lithium oxide, strontium lithium oxide, tin lithium oxide, antimony lithium oxide, niobium lithium oxide, molybdenum lithium oxide, yttrium lithium oxide and aluminum lithium oxide.

[0090] As an example, the carbide in the coating layer is selected from at least two of lanthanum carbide, cerium carbide, tantalum carbide, tungsten carbide, zirconium carbide, titanium carbide, strontium carbide, tin carbide, antimony carbide, niobium carbide, molybdenum carbide, yttrium carbide and aluminum carbide.

[0091] Optionally, the M element also includes F;

[0092] The coating layer further includes fluoride, and the fluoride contains A element and B element.

[0093] In this way, the M element includes C and F, the coating layer includes lithium oxide, carbide and fluoride, and the lithium oxide, carbide and fluoride each independently contain the A element and the B element. The introduction of an appropriate amount of fluorine can replace the oxygen element, reduce the active sites on the surface that can react with water and carbon dioxide in the air, and further enhance the air stability of the positive electrode lithium supplement. In addition, fluorine and carbon elements can also form carbon fluoride to enhance the hydrophobicity of the surface, thereby improving the air stability of the positive electrode lithium supplement in a high humidity environment.

[0094] As an example, the fluoride in the coating layer is selected from at least two of lanthanum fluoride, cerium fluoride, tantalum fluoride, tungsten fluoride, zirconium fluoride, titanium fluoride, strontium fluoride, tin fluoride, antimony fluoride, niobium fluoride, molybdenum fluoride, yttrium fluoride and aluminum fluoride.

[0095] Optionally, the A element includes at least one of Ce, Ta, Ti, Sr, Sn, Sb and Al, and the B element includes at least one of La, W, B, Zr, Mo, Y and Nb.

[0096] Optionally, the A element is selected from at least one of Ta, Ti and Ce, and the B element is selected from Nb.

[0097] Optionally, the coating layer has a thickness of 1 nm to 25 nm, and further optionally 5 nm to 12 nm. As an example, the coating layer has a thickness of 1 nm, 2 nm, 4 nm, 5 nm, 6 nm, 8 nm, 10 nm, 12 nm, 14 nm, 15 nm, 16 nm, 18 nm, 20 nm, 22 nm, 24 nm, and 25 nm.

[0098] Optionally, the mass proportion of the coating layer in the positive electrode lithium supplement agent is 0.1% to 3%, and further optionally 0.5% to 1.5%. As an example, the mass proportion of the coating layer in the positive electrode lithium supplement agent can be 0.1%, 0.2%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, 2%, 2.2%, 2.4%, 2.5%, 2.6%, 2.8% and 3%.

[0099] Optionally, the median particle size (D50) of the positive electrode lithium supplement is 5μm-10μm, and further optionally 6μm-8μm. As an example, the D50 of the positive electrode lithium supplement can be 5μm, 5.5μm, 6μm, 6.5μm, 7μm, 7.5μm, 8μm, 8.5μm, 9μm, 9.5μm and 10μm.

[0100] In a second aspect of the present application, a method for preparing the positive electrode lithium supplement as described above is provided.

[0101] In some embodiments, the preparation method of the positive electrode lithium supplement comprises the following steps:

[0102] S200: mixing lithium-rich nickel oxide, reducing organic matter and coating material to prepare a second powder;

[0103] S300: calcining the second powder under an inert atmosphere to prepare a positive electrode lithium supplement;

[0104] The coating material includes source A and source B, and source A and / or source B include metal organic matter.

[0105] The present application uses reducing organic matter and coating materials to modify lithium-rich nickel oxide (Li2NiO2) to form a positive electrode lithium supplement with a core-shell structure. The A element and the B element in the coating material react with the active lithium to generate lithium oxide and coat the surface of the positive electrode lithium supplement, which is beneficial to reduce the free lithium content and residual alkali content on the surface, thereby inhibiting gas production and improving processing performance. The A source and / or the B source in the coating material include metal organic matter, which will decompose during the calcination process and can be used as an organic carbon source to promote the formation of carbon doping in the core and the formation of amorphous carbide in the coating layer. The reducing organic matter has mild reducing properties and can undergo redox reactions with the A source and / or B source in the coating material. On the one hand, it can assist in the formation of carbides containing elements A and B, preventing the product from being converted into a single carbon substance, and on the other hand, it can promote the formation of oxygen vacancies, thereby obtaining an amorphous carbide coating containing oxygen vacancies; at the same time, the reducing organic matter also plays a role in combustion, and it will decompose rapidly during the calcination process, generating a large amount of small molecule gas and diffusing to the surface of the material, so that the raw materials are evenly mixed, thereby forming a uniform and stable coating. The coating can not only prevent the positive electrode lithium supplement from having side reactions with water vapor in the air and improve air stability, but also play a role in adsorbing lattice oxygen, preventing the lattice oxygen from forming oxygen and escaping from the positive electrode lithium supplement, thereby effectively inhibiting the gas production side reaction.

[0106] The preparation method of the positive electrode lithium supplement is described in detail below in a step-by-step manner.

[0107] Before step S200, the method further includes step S100: preparing lithium-rich lithium nickel oxide.

[0108] Optionally, the method for preparing lithium-rich lithium nickelate comprises the following steps:

[0109] S110: mixing a lithium source and a nickel source to prepare a first powder;

[0110] S120: Sintering the first powder in an inert atmosphere to prepare lithium-rich lithium nickel oxide.

[0111] Optionally, the lithium source includes at least one of lithium oxide (Li2O), lithium hydroxide (LiOH), lithium carbonate (Li2CO3), lithium nitrate (LiNO3), lithium acetate (CH3COOLi) and lithium oxalate (Li2C2O4), and may further be at least one of lithium oxide and lithium hydroxide.

[0112] Optionally, the nickel source includes at least one of nickel oxide (NiO), nickel hydroxide (Ni(OH)2), nickel nitrate (Ni(NO3)2), nickel chloride (NiCl2) and nickel sulfate (NiSO4), and may further be nickel oxide.

[0113] It can be understood that the lithium source and the nickel source can be compounds containing bound water, such as lithium hydroxide monohydrate (LiOH·H2O), or compounds not containing bound water, such as anhydrous lithium carbonate.

[0114] Optionally, the BET specific surface area of ​​the lithium source and the nickel source is independently 5 m 2 / g~10m 2 / g, for example 5m 2 / g, 6m 2 / g, 7m 2 / g, 8m 2 / g, 9m 2 / g and 10m 2 / g.

[0115] Optionally, the median particle size (D50) of the lithium source and the nickel source is each independently 1 μm to 3 μm, for example 1 μm, 1.2 μm, 1.5 μm, 1.8 μm, 2 μm, 2.2 μm, 2.5 μm, 2.8 μm and 3 μm.

[0116] Optionally, the molar ratio of lithium in the lithium source to nickel in the nickel source is (1.8-2.0):1, and further optionally (1.95-2.0):1. As an example, the molar ratio of lithium in the lithium source to nickel in the nickel source may be 1.8:1, 1.85:1, 1.9:1, 1.95:1 and 2.0:1. It can be understood that the molar ratio of lithium to nickel in the lithium-rich nickel oxide is also (1.8-2.0):1, that is, the expression of the lithium-rich nickel oxide is Li a NiO2, and a=1.8~2.0.

[0117] Optionally, the method of mixing the lithium source and the nickel source comprises a ball milling method. Specifically, the lithium source and the nickel source are subjected to ball milling to mix them uniformly; the equipment for ball milling the lithium source and the nickel source is a vacuum ball mill with a rotation speed of 400 rpm to 700 rpm and a time of 0.5 h to 2 h.

[0118] Optionally, the inert atmosphere of the sintering process includes at least one of nitrogen, helium, neon, argon, krypton and xenon, and may further be nitrogen or argon.

[0119] Optionally, the sintering temperature of the sintering process is 700° C. to 800° C., and further optionally 740° C. to 760° C. As an example, the sintering temperature of the sintering process may be 700° C., 710° C., 720° C., 730° C., 740° C., 750° C., 760° C., 770° C., 780° C., 790° C., and 800° C.

[0120] Optionally, the sintering time of the sintering process is 15h~20h, and further optionally 13h~16h. As an example, the sintering time of the sintering process can be 15h, 15.5h, 16h, 16.5h, 17h, 17.5h, 18h, 18.5h, 19h, 19.5h and 20h.

[0121] Optionally, the heating rate of the sintering process is 0.5°C / min to 3°C / min, and further optionally 1°C / min to 2°C / min. As an example, the heating rate of the sintering process may be 0.5°C / min, 1°C / min, 1.5°C / min, 2°C / min, 5.5°C / min, and 3°C / min.

[0122] Optionally, after the sintering treatment, the following steps are further included: cooling the sintered product, and then subjecting the product to ball milling and / or crushing treatment to make the median particle size (D50) of the lithium-rich nickel oxide to be 6 μm to 9 μm.

[0123] S200: mixing lithium-rich nickel oxide, reducing organic matter and coating material to prepare a second powder.

[0124] Optionally, the reducing organic matter comprises at least one of urea, glycine and citric acid. Further optionally, the reducing organic matter comprises urea.

[0125] Optionally, the source A includes at least one of an oxide, a fluoride, a hydroxide and an ethoxide of element A. Further optionally, the source A includes at least one of tantalum oxide, titanium oxide and cerium fluoride.

[0126] Optionally, the B source includes at least one of an oxide, a fluoride, a hydroxide and an ethoxide of the element B. Further optionally, the B source includes niobium ethoxide.

[0127] It can be understood that the coating material can not only serve as a doping source for element A and a doping source for element B, but also as an organic carbon source or a fluorine source. Specifically, the ethanolate of element A and / or element B serves as an organic carbon source, which decomposes to form corresponding carbides during the calcination process, thereby enhancing the air stability of the positive electrode lithium replenisher. The fluoride of element A and / or element B can be used as a fluorine source to dope the positive electrode lithium replenisher with a certain amount of fluorine, reduce the active sites on the surface that can react with water vapor and carbon dioxide, and further enhance the air stability of the positive electrode lithium replenisher. In addition, carbon fluoride may also form between carbon and fluorine, thereby enhancing the hydrophobicity of the positive electrode lithium replenisher.

[0128] Optionally, in the second powder, the mass ratio of lithium-rich nickel oxide, reducing organic matter, source A and source B is 100: (0.1-0.8): (0.01-5): (0.01-5), and can further be 100: (0.3-0.7): (0.1-3.5): (0.5-3.5). As an example, the mass ratio of lithium-rich nickel oxide and reducing organic matter can be 100: 0.1, 100: 0.2, 100: 0.3, 100: 0.4, 100: 0.5, 100: 0.6, 100: 0.7 or 100: 0.8; the mass ratio of lithium-rich nickel oxide and source A can be 100: 0.01, 100: 0.05, 100: 0.1, 100: 0.2, 100: 0.3, 100: 0.4, 100: 0.5, 100: 0.6, 100: 0.7 or 100: 0.8. The mass ratio of the lithium-rich nickel oxide to the B source can be 100:0.01, 100:0.05, 100:0.1, 100:0.2, 100:0.5, 100:0.8, 100:1, 100:2, 100:3, 100:4 or 100:5.

[0129] Optionally, the method of mixing the lithium-rich nickel acid, the reducing organic matter and the coating material comprises a ball milling method. Specifically, the lithium-rich nickel acid, the reducing organic matter and the coating material are subjected to ball milling to mix them uniformly; the equipment for ball milling the lithium-rich nickel acid, the reducing organic matter and the coating material is a vacuum ball mill with a rotation speed of 400 rpm to 600 rpm and a time of 1 hour to 4 hours.

[0130] S300: calcining the second powder under an inert atmosphere to prepare a positive electrode lithium supplement;

[0131] Optionally, the inert atmosphere of the calcination treatment includes at least one of nitrogen, helium, neon, argon, krypton and xenon, and may further be nitrogen or argon.

[0132] Optionally, the calcination temperature of the calcination treatment is 500° C. to 800° C. As an example, the calcination temperature of the calcination treatment may be 500° C., 550° C., 600° C., 650° C., 700° C., 750° C., and 800° C.

[0133] Optionally, the calcination time of the calcination treatment is 5 h to 10 h. As an example, the calcination time of the calcination treatment can be 5 h, 5.5 h, 6 h, 6.5 h, 7 h, 7.5 h, 8 h, 8.5 h, 9 h, 9.5 h and 10 h.

[0134] In a third aspect of the present application, a positive electrode sheet is provided, which is an application of the positive electrode lithium supplement agent as described above in the field of lithium-ion batteries.

[0135] Optionally, the positive electrode sheet includes a positive electrode current collector and a positive electrode active layer covering the positive electrode current collector; wherein the positive electrode active layer includes the positive electrode lithium replenisher as described above, or includes the positive electrode lithium replenisher prepared by the preparation method of the positive electrode lithium replenisher as described above.

[0136] It can be understood that the positive electrode active layer covers at least one surface of the positive electrode current collector.

[0137] Optionally, the positive electrode current collector includes a metal foil or a composite current collector. The metal foil may be aluminum foil; the composite current collector includes a polymer substrate and a metal layer formed on the polymer substrate, the polymer substrate may be made of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS) and polyethylene (PE), and the metal layer may be made of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy.

[0138] Optionally, the mass proportion of the positive electrode lithium supplement in the positive electrode active layer is 1% to 10%, and further optionally 1% to 5%. As an example, the mass proportion of the positive electrode lithium supplement in the positive electrode active layer can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% and 10%.

[0139] When the positive electrode active layer contains 1% to 10% of the positive electrode lithium supplement, there can be an appropriate amount of lithium supplement to make up for the loss of active lithium, but it will not lead to too little positive electrode active material, resulting in the reversible lithium insertion vacancies in the positive electrode active layer being supplemented and reducing the energy density of the battery.

[0140] Optionally, the positive electrode active layer further includes a positive electrode active material, and the mass ratio of the positive electrode active material to the lithium supplement is 1: (0.03-0.1), and further optionally 1: (0.03-0.05). As an example, the mass ratio of the positive electrode active material to the lithium supplement may be 1: 0.03, 1: 0.04, 1: 0.05, 1: 0.06, 1: 0.07, 1: 0.08, 1: 0.09, and 1: 0.1.

[0141] Optionally, the positive electrode active material is a positive electrode active material for lithium ion batteries known in the art. As an example, the positive electrode active material can be at least one of a lithium transition metal oxide and an olivine structured lithium phosphate. The lithium transition metal oxide includes but is not limited to: lithium cobalt oxide, such as LiCoO2; lithium nickel oxide, such as LiNiO2; lithium manganese oxide, such as LiMnO2 or LiMn2O4; lithium nickel cobalt oxide; lithium manganese cobalt oxide; lithium nickel manganese oxide; lithium nickel cobalt manganese oxide, such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2(NCM 333 )、LiNi 0.5 Co 0.2 Mn 0.3 O2(NCM 523 )、LiNi 0.5 Co 0.25 Mn 0.25 O2(NCM 211 )、LiNi 0.6 Co 0.2 Mn 0.2 O2(NCM 622 )、LiNi 0.8 Co 0.1 Mn 0.1 O2(NCM 811 ); lithium nickel cobalt aluminum oxide, such as LiNi 0.8 Co 0.15 Al 0.05 O2; and modified compounds of the above-mentioned lithium transition metal oxides. Lithium-containing phosphates with an olivine structure include, but are not limited to: lithium iron phosphate, such as LiFePO4 (LFP); a composite material of lithium iron phosphate and carbon; lithium manganese phosphate, such as LiMnPO4; a composite material of lithium manganese phosphate and carbon; lithium iron manganese phosphate; a composite material of lithium iron manganese phosphate and carbon; and modified compounds of the above-mentioned lithium-containing phosphates with an olivine structure. The modified compound of each material may be at least one of doping modification and surface coating modification.

[0142] Optionally, the positive electrode active layer further includes a binder to improve the bonding strength between the positive electrode active layer and the positive electrode current collector. The binder includes at least one of polyvinylidene fluoride (PVDF), sodium alginate (SA), polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), hydrogenated nitrile rubber (HNBR), polytetrafluoroethylene (PTFE), and polyacrylic acid (PAA).

[0143] Optionally, the positive electrode active layer further includes a conductive agent, and the conductive agent includes at least one of conductive carbon, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon quantum dots, carbon nanotubes, graphene and carbon nanofibers.

[0144] Optionally, in the positive electrode active layer, the mass ratio of the positive electrode active material, the conductive agent and the binder is (8-9.5): (0.25-1): (0.25-1).

[0145] Optionally, the preparation method of the positive electrode sheet includes the following steps: dispersing the positive electrode active material, the conductive agent, the binder and the positive electrode lithium supplement in an organic solvent to prepare a positive electrode slurry; covering the positive electrode slurry on at least one surface of the positive electrode current collector, and obtaining the positive electrode sheet after drying, rolling and cutting. The organic solvent is selected from N-methylpyrrolidone (NMP); the solid content of the positive electrode slurry is 20% to 50%, and can be further selected as 30%; the drying temperature is 100°C to 150°C, the time is 60min to 120min, and can be further selected as drying at 120°C for 80min.

[0146] In a fourth aspect of the present application, a lithium-ion battery is provided, comprising the positive electrode sheet as described above.

[0147] As can be understood, lithium-ion batteries include positive and negative electrodes, electrolytes, and separators. During the charge and discharge cycle, active lithium ions are intercalated and deintercalated between the positive and negative electrodes; the electrolyte conducts lithium ions between the positive and negative electrodes; and the separator is located between the positive and negative electrodes to prevent short circuits while allowing lithium ions to pass through.

[0148] Optionally, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer covering at least one surface of the negative electrode current collector.

[0149] Optionally, the negative electrode current collector includes a metal foil or a composite current collector. The metal foil in the negative electrode current collector may be copper foil. The composite current collector in the negative electrode current collector is substantially the same as that in the positive electrode current collector and will not be described in detail.

[0150] Optionally, the negative electrode active layer includes a negative electrode active material, and the negative electrode active material includes at least one of elemental silicon, silicon oxide, a silicon-carbon composite, a silicon-nitrogen composite, and a silicon alloy material.

[0151] Optionally, the negative electrode active layer further includes a binder, and the binder includes at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0152] Optionally, the negative electrode active layer further includes a conductive agent, and the conductive agent includes at least one of conductive carbon, superconducting carbon, acetylene black, carbon black, Ketjen black, carbon quantum dots, carbon nanotubes, graphene and carbon nanofibers.

[0153] It is understood that the electrolyte in a lithium-ion battery can be liquid, gel or all-solid.

[0154] Optionally, the electrolyte adopts an electrolyte solution, which includes a lithium salt and an organic solvent. Among them, the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl imide), lithium bis(trifluoromethanesulfonyl imide), lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate and lithium tetrafluorooxalate phosphate; the organic solvent includes at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0155] Optionally, the electrolyte further includes additives, such as negative electrode film-forming additives, positive electrode film-forming additives, additives for improving battery overcharge performance, additives for improving battery high or low temperature performance, etc.

[0156] It is understandable that the separator can be a porous separator with good chemical stability and mechanical stability; at the same time, the separator can be a single-layer film or a multi-layer composite film. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without special restrictions.

[0157] Optionally, the material of the diaphragm includes at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride.

[0158] It can be understood that the lithium-ion battery of the present application includes a battery cell form, a battery module form and a battery pack form. The shape of the lithium-ion battery can be cylindrical, square or other arbitrary shapes.

[0159] Optionally, the positive electrode sheet, the negative electrode sheet and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0160] Optionally, the lithium-ion battery may include an outer package for encapsulating the electrode assembly and the electrolyte. The outer package of the lithium-ion battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer package of the lithium-ion battery may also be a soft package, such as a bag-type soft package, and the material of the soft package may be plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate, etc.

[0161] Optionally, the battery cells can be assembled into a battery module, and the number of battery cells contained in the battery module can be one or more. The battery modules can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more.

[0162] Optionally, the battery cells, battery modules, and battery packs can be used as power sources for electrical devices or as energy storage units for electrical devices. Electrical devices include, but are not limited to: mobile devices, such as mobile phones, tablet computers, and laptop computers; electric vehicles, such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.; electric trains; ships; satellites; and energy storage systems.

[0163] The following is further described in conjunction with specific embodiments and comparative examples. The raw materials involved in the following specific embodiments and comparative examples, unless otherwise specified, can all be commercially available, the instruments used, unless otherwise specified, can all be commercially available, and the processes involved, unless otherwise specified, are all routinely selected by those skilled in the art.

[0164] Example 1

[0165] In this embodiment, the A element is Ta, the B element is Nb, and the M element is C.

[0166] The preparation method of the positive electrode lithium supplement agent of this embodiment comprises the following steps:

[0167] (1) Preparation of lithium-rich nickel oxide: lithium hydroxide and nickel oxide are prepared according to a molar ratio of Li:Ni=2:1, and placed in a vacuum ball mill, and ball milled at a speed of 500 rpm for 1 hour to mix evenly to obtain a first powder; in a nitrogen atmosphere, the temperature is increased to 750°C at a heating rate of 2°C / min, and sintered at 750°C for 16 hours. After cooling in the furnace, ball milling and crushing are performed to obtain lithium-rich nickel oxide (Li2NiO2).

[0168] (2) Preparation of positive electrode lithium supplement: lithium nickel-rich lithium oxide, urea, tantalum oxide and niobium ethanol were prepared in a mass ratio of 100:0.6:0.3:1, and placed in a vacuum ball mill, ball milled at a speed of 500 rpm for 2 hours to mix evenly to obtain a second powder; calcined at 500 ° C for 10 hours in a nitrogen atmosphere, and cooled with the furnace to obtain a positive electrode lithium supplement, the core of which is Li2Ni 0.999954 Ta 0.00001 4Nb 0.000032 C 0.00003 O2, the coating layer contains tantalum lithium oxide, niobium lithium oxide, tantalum carbide and niobium carbide, and the tantalum carbide and niobium carbide have oxygen vacancies.

[0169] Example 2

[0170] In this embodiment, the A element is Ti, the B element is Nb, and the M element is C.

[0171] The preparation method of the positive electrode lithium supplement agent of this embodiment comprises the following steps:

[0172] (1) Preparation of lithium-rich nickel oxide: lithium hydroxide, lithium oxide and nickel oxide are prepared according to a molar ratio of Li:Ni=2:1 and a molar ratio of lithium hydroxide to lithium oxide of 0.93:0.1, and are placed in a vacuum ball mill and ball-milled at a speed of 500 rpm for 1 hour to mix them evenly to obtain a first powder; in a nitrogen atmosphere, the temperature is increased to 750°C at a heating rate of 2°C / min, and sintered at 750°C for 16 hours. After cooling in the furnace, the powder is ball-milled and crushed to obtain lithium-rich nickel oxide (Li2NiO2).

[0173] (2) Preparation of positive electrode lithium supplement: lithium nickel oxide, urea, titanium dioxide and niobium ethanol were prepared in a mass ratio of 100:0.6:0.3:1, and placed in a vacuum ball mill, ball milled at a speed of 500 rpm for 2 hours to mix evenly to obtain a second powder; calcined at 500 ° C for 5 hours in a nitrogen atmosphere, and cooled with the furnace to obtain a positive electrode lithium supplement, the core of which is Li2Ni 0.999929 Ti 0.000039 Nb 0.000032 C 0.00003 O2, the coating layer contains titanium lithium oxide, niobium lithium oxide, titanium carbide and niobium carbide, and the titanium carbide and niobium carbide have oxygen vacancies.

[0174] Example 3

[0175] In this embodiment, the A element is Ce, the B element is Nb, and the M element is C and F.

[0176] The preparation method of the positive electrode lithium supplement agent of this embodiment comprises the following steps:

[0177] (1) Preparation of lithium-rich nickel oxide: lithium oxide, lithium hydroxide and nickel oxide were prepared according to a molar ratio of Li:Ni=1.96:1 and a molar ratio of lithium oxide to lithium hydroxide of 0.95:0.1, and placed in a vacuum ball mill, ball milled at a speed of 500 rpm for 1 hour to mix evenly to obtain a first powder; in a nitrogen atmosphere, the temperature was increased to 750°C at a heating rate of 2°C / min, and sintered at 750°C for 16 hours. After cooling in the furnace, ball milling and crushing were performed to obtain lithium-rich nickel oxide (Li 1.96 NiO2).

[0178] (2) Preparation of positive electrode lithium supplement: prepare lithium nickel-rich lithium oxide, urea, cerium fluoride and niobium ethanol in a mass ratio of 100:0.6:0.3:1, place in a vacuum ball mill, and ball mill at a speed of 500 rpm for 2 hours to mix evenly to obtain a second powder; calcine at 500 ° C for 10 hours in a nitrogen atmosphere, and cool with the furnace to obtain a positive electrode lithium supplement, the core of which is Li2Ni 0.999952 Ce 0.00001 6Nb 0.000032 C 0.00003 F 0.000048 O2, the coating layer contains lithium cerium oxide, lithium niobium oxide, cerium carbide, niobium carbide, cerium fluoride and niobium fluoride, and the cerium carbide and niobium carbide have oxygen vacancies.

[0179] Example 4

[0180] In this embodiment, the A element is Ce, the B element is Nb, and the M element is C and F.

[0181] The preparation method of the positive electrode lithium supplement agent of this embodiment comprises the following steps:

[0182] (1) Preparation of lithium-rich nickel oxide: lithium hydroxide, lithium oxide and nickel oxide were prepared according to a molar ratio of Li:Ni=1.98:1 and a molar ratio of lithium hydroxide to lithium oxide of 0.91:0.1, and placed in a vacuum ball mill, ball milled at a speed of 500 rpm for 1 hour to mix evenly to obtain a first powder; in a nitrogen atmosphere, the temperature was increased to 750°C at a heating rate of 2°C / min, and sintered at 750°C for 16 hours. After cooling in the furnace, ball milling and crushing were performed to obtain lithium-rich nickel oxide (Li 1.98 NiO2).

[0183] (2) Preparation of positive electrode lithium supplement: lithium nickel oxide, urea, cerium fluoride and niobium ethanol were prepared in a mass ratio of 100:0.6:0.3:1, and placed in a vacuum ball mill, ball milled at a speed of 500 rpm for 2 hours to mix evenly to obtain a second powder; calcined at 700 ° C for 10 hours in a nitrogen atmosphere, and cooled with the furnace to obtain a positive electrode lithium supplement, the core of which is Li2Ni0.999952 Ce 0.00001 6Nb 0.000032 C 0.00003 F 0.000048 O2, the coating layer contains lithium cerium oxide, lithium niobium oxide, cerium carbide, niobium carbide, cerium fluoride and niobium fluoride, and the cerium carbide and niobium carbide have oxygen vacancies.

[0184] Example 5

[0185] This embodiment is basically the same as embodiment 1, except that the sintering temperature in step (1) is 700°C.

[0186] Example 6

[0187] This embodiment is basically the same as embodiment 1, except that the sintering temperature in step (1) is 800°C.

[0188] Example 7

[0189] This embodiment is basically the same as embodiment 1, except that the sintering time in step (1) is 20 hours.

[0190] Example 8

[0191] This embodiment is basically the same as embodiment 1, except that the calcination temperature in step (2) is 800°C.

[0192] Example 9

[0193] This embodiment is basically the same as embodiment 1, except that the calcination time in step (2) is 5 hours.

[0194] Example 10

[0195] This embodiment is basically the same as embodiment 1, except that the calcination condition in step (2) is calcination at 800° C. for 5 h.

[0196] Embodiment 11

[0197] This embodiment is substantially the same as the embodiment 1, except that the mass ratio of lithium-rich nickel oxide, urea, tantalum oxide and niobium ethoxide is 100:0.1:0.3:1.

[0198] Example 12

[0199] This embodiment is substantially the same as the embodiment 1, except that the mass ratio of lithium-rich nickel oxide, urea, tantalum oxide and niobium ethoxide is 100:0.8:0.3:1.

[0200] Embodiment 13

[0201] This embodiment is substantially the same as the embodiment 1, except that the mass ratio of lithium-rich nickel oxide, urea, tantalum oxide and niobium ethoxide is 100:0.6:0.1:1.

[0202] Embodiment 14

[0203] This embodiment is substantially the same as the embodiment 1, except that the mass ratio of lithium-rich nickel oxide, urea, tantalum oxide and niobium ethoxide is 100:0.6:5:1.

[0204] Embodiment 15

[0205] This embodiment is substantially the same as the embodiment 1, except that the mass ratio of lithium-rich nickel oxide, urea, tantalum oxide and niobium ethoxide is 100:0.6:0.3:0.1.

[0206] Example 16

[0207] This embodiment is substantially the same as the embodiment 1, except that the mass ratio of lithium-rich nickel oxide, urea, tantalum oxide and niobium ethoxide is 100:0.6:0.3:5.

[0208] Comparative Example 1

[0209] This comparative example uses the traditional positive electrode lithium supplement Li2NiO2.

[0210] Comparative Example 2

[0211] This comparative example is basically the same as Example 1, except that: in step (2), source B (niobium ethanolate) is not added, only source A (tantalum oxide) is added, the mass ratio of lithium nickel-rich lithium oxide, urea and tantalum oxide is 100:0.6:1, and the core of the positive electrode lithium supplement is Li2Ni 0.999954 Ta 0.000046 C 0.00004 O2, the coating layer contains tantalum lithium oxide and tantalum carbide, and the tantalum carbide has oxygen vacancies.

[0212] Comparative Example 3

[0213] This comparative example is basically the same as Example 1, except that: in step (2), source A (tantalum oxide) is not added, only source B (niobium ethoxide) is added, the mass ratio of lithium-rich nickel oxide, urea and niobium ethoxide is 100:0.6:1, and the core of the positive electrode lithium supplement is Li2Ni 0.999968 Nb 0.000032 C 0.00003 O2, the coating layer contains niobium lithium oxide and niobium carbide, and the niobium carbide has oxygen vacancies.

[0214] Comparative Example 4

[0215] This comparative example is basically the same as Example 1, except that niobium ethanol is replaced by niobium oxide, and the core of the positive electrode lithium supplement is Li2Ni 0.999954 Ta 0.000014 Nb 0.000032 O2, the coating layer contains tantalum lithium oxide and niobium lithium oxide.

[0216] Comparative Example 5

[0217] This comparative example is basically the same as Example 1, except that no urea is added during the calcination process, and the core of the positive electrode lithium supplement is Li2Ni 0.999954 Ta 0.000014 Nb 0.000032 O2, the coating layer contains tantalum lithium oxide, niobium lithium oxide and carbon element.

[0218] Test Case

[0219] (1) The element distribution of the positive electrode lithium supplement agent of Example 1 was tested by EDS spectrum analysis. The results are shown in Figure 1 .in, Figure 1 Figure (a) shows the carbon element distribution on the surface of the positive electrode lithium supplement. Figure 1 Figure (b) shows the distribution of niobium elements on the surface of the positive electrode lithium supplement. Figure 1 It can be seen that the surface of the positive electrode lithium supplement agent of Example 1 contains uniformly distributed carbon elements and niobium elements.

[0220] (2) The Raman spectrum of the positive electrode lithium supplement agent of Example 1 was tested by Raman analysis. The results are shown in Figure 2 .Depend on Figure 2 It can be seen that the surface of the positive electrode lithium supplement agent contains Nb-C bonds, which means that a coating layer containing niobium carbide is formed on the surface of the positive electrode lithium supplement agent.

[0221] (3) The median particle size (D50) of the positive electrode lithium supplement was measured by SEM. Figure 3~Figure 6 and Table 1 to Table 3; among which, Figure 3 This is a SEM image of the positive electrode lithium supplement agent of Example 1. Figure 4 This is a SEM image of the positive electrode lithium supplement agent of Example 2. Figure 5 This is a SEM image of the positive electrode lithium supplement agent of Example 3. Figure 6 This is a SEM image of the positive electrode lithium supplement agent of Example 4. As can be seen from Tables 1 and 2, the D50 of the positive electrode lithium supplement agents prepared in Examples 1 to 16 is between 6.2 μm and 9.8 μm, and the particle size is relatively uniform.

[0222] (4) The molar ratio of lithium to nickel in the positive electrode lithium supplement was measured by ICP analysis, and the purity of Li2NiO2 in the positive electrode lithium supplement was tested by XRD. The results are shown in Tables 1 to 3. As shown in Tables 1 to 2, the Li / Ni of the positive electrode lithium supplement prepared in Examples 1 to 16 is between 1.76 and 1.88, and the purity of Li2NiO2 reaches 87.8% to 94.9%.

[0223] (5) The coating thickness of the positive electrode lithium supplement agent was measured by TEM, and the results are shown in Tables 1 to 3. As shown in Tables 1 to 2, the coating thickness of the positive electrode lithium supplement agent prepared in Examples 1 to 16 is between 1 nm and 22 nm.

[0224] (6) A positive electrode lithium supplement was added to the button battery, and the button battery was subjected to charge and discharge tests to obtain the charge gram capacity, discharge gram capacity, charge and discharge efficiency, and irreversible capacity of the button battery during the first charge and discharge cycle. The results are shown in Table 4. The charge and discharge test method is as follows:

[0225] The positive electrode active material, the positive electrode lithium replenisher, the conductive carbon and the binder are dispersed in an organic solvent, mixed evenly, and the fineness is ensured to be ≤20 μm and the viscosity is 4000 mPa·s~6000 mPa·s to prepare a positive electrode slurry; wherein the positive electrode active material is the nickel-cobalt-manganese ternary material S85EN, the positive electrode lithium replenisher is selected from one of the embodiments or comparative examples, the binder is PVDF, the organic solvent is NMP, the mass ratio of the positive electrode active material to the positive electrode lithium replenisher is 1:0.04, the mass ratio of the positive electrode active material, the conductive carbon and the binder is 8:1.5:0.5, and the solid content of the positive electrode slurry is 30%.

[0226] After the positive electrode slurry is passed through a 200-mesh screen, it is evenly coated on the two surfaces of the positive electrode current collector (aluminum foil) with a scraper and dried at 120°C for 80 minutes. The surface density of the coating is 360 g / m 2 ~380g / m 2 The semi-finished electrode after coating is rolled and sliced, and the compaction density is 3.2g / cm 3 ~3.45g / cm 3 ; Assemble the positive electrode sheet and the corresponding negative electrode sheet (silicon oxide negative electrode), separator and electrolyte (lithium hexafluorophosphate electrolyte) into a button battery for charge and discharge test: the battery's charge and discharge voltage window is 2.5V~4.3, the test is charged at 0.2C (0.2 times the rated capacity), discharged at 0.2C, and the temperature is 25℃.

[0227] As can be seen from Table 4, after the button-type batteries are added with the positive electrode lithium supplement agents of Examples 1 to 16, the charge and discharge efficiency can reach 33%, and the irreversible capacity can reach 307.3 mAh / g, which is significantly better than Comparative Examples 1 to 5, proving that the positive electrode lithium supplement agents of Examples 1 to 16 are beneficial to improving the charge and discharge efficiency and battery capacity of the battery.

[0228] (7) A button cell was prepared according to step (6), and the button cell was subjected to formation treatment. The volume of the button cell was measured and recorded as V1. The button cell was kept at 70°C for a period of time (7 days, 14 days or 21 days), and then soaked in hot water at 70°C for 1 min. The cell was taken out and the volume of the button cell was measured and recorded as V2. The volume growth rate of the cell was calculated according to (V2-V1) / V1×100%. The results are shown in Table 5.

[0229] As shown in Table 5, after the button-type batteries were added with the positive electrode lithium replenishers of Examples 1 to 16 and placed at 70°C for 7 to 21 days, the volume growth rate was significantly lower than that of Comparative Examples 1 to 5, proving that the gas production side reaction of the positive electrode lithium replenishers of Examples 1 to 16 was effectively suppressed. In addition, according to Comparative Examples 2 to 3, it can be seen that the doping of a single tantalum element or a single niobium element has limited effect on reducing the residual alkali on the surface of the positive electrode lithium replenisher, and cannot effectively reduce the reaction with the electrolyte. At the same time, the coating layer cannot form an effective carbide coating network, and it is difficult to suppress the release of lattice oxygen. Therefore, the volume growth rate is equivalent to that of Comparative Example 1.

[0230] Table 1. Preparation process parameters and physical properties of positive electrode lithium supplement agents of Examples 1 to 4

[0231]

[0232] Table 2. Performance of positive electrode lithium supplements of Examples 5 to 16

[0233]

[0234] Table 3. Preparation process parameters and physical properties of positive electrode lithium supplement agents in comparative examples 1 to 5

[0235]

[0236] Table 4. First charge and discharge test results of button cell at 0.2C

[0237]

[0238] Table 5. Volume growth rate test results of button batteries

[0239]

[0240] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0241] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of protection of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the scope of protection of the present application. Therefore, the scope of protection of the present application shall be subject to the attached claims.

Claims

1. A method for preparing a positive electrode lithium supplement, characterized in that: The following steps are involved: Mixing lithium-rich nickel oxide, reducing organic matter and coating material to prepare a second powder; calcining the second powder in a nitrogen atmosphere or an inert atmosphere to prepare the positive electrode lithium supplement agent; Wherein, the coating material comprises an A source and a B source, the A source comprises at least one of tantalum oxide, titanium oxide and cerium fluoride, and the B source comprises niobium ethoxide; The reducing organic matter includes urea; In the second powder, the mass ratio of the lithium-rich nickel oxide, the reducing organic matter, the source A and the source B is 100: (0.1-0.8): (0.01-5): (0.01-5); The method of mixing the lithium-rich nickel oxide, the reducing organic matter and the coating material includes ball milling; The inert atmosphere of the calcination treatment includes at least one of helium, neon, argon, krypton and xenon; The calcination temperature of the calcination treatment is 500°C to 800°C; The calcination time of the calcination treatment is 5h~10h; The core of the positive electrode lithium supplement comprises a modified lithium-rich nickel oxide containing elements A, B and M, wherein the M element comprises C; The coating layer of the positive electrode lithium supplement agent includes lithium oxide and carbide each independently containing the A element and the B element, and the carbide has oxygen vacancies.

2. The method for preparing a positive electrode lithium supplement according to claim 1, characterized in that: The preparation method of the lithium-rich nickel oxide comprises the following steps: Mixing a lithium source and a nickel source to prepare a first powder; The first powder is sintered in a nitrogen atmosphere or an inert atmosphere to prepare the lithium-rich lithium nickel oxide.

3. The method for preparing a positive electrode lithium supplement as claimed in claim 2, characterized in that: One or more of the following conditions are met: (1) The lithium source includes at least one of lithium oxide, lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate and lithium oxalate; (2) The nickel source includes at least one of nickel oxide, nickel hydroxide, nickel nitrate, nickel chloride and nickel sulfate; (3) The BET specific surface area of ​​the lithium source and the nickel source is independently 5 m 2 / g~10m 2 / g; (4) The median particle size of the lithium source and the nickel source is independently 1 μm to 3 μm; (5) The molar ratio of the lithium element in the lithium source to the nickel element in the nickel source is (1.8-2.0):1; (6) Methods for mixing the lithium source and the nickel source include ball milling; (7) The inert atmosphere of the sintering process includes at least one of helium, neon, argon, krypton and xenon; (8) The sintering temperature of the sintering treatment is 700°C to 800°C; (9) The sintering time of the sintering treatment is 15h~20h; (10) The heating rate of the sintering process is 0.5°C / min~3°C / min.

4. A positive electrode lithium supplement, characterized in that: Prepared by the preparation method of the positive electrode lithium supplement agent according to any one of claims 1 to 3; The positive electrode lithium supplement comprises a core and a coating layer covering the core; The core includes modified lithium-rich nickel acid, the modified lithium-rich nickel acid contains an A element, a B element and an M element, the A element is selected from at least one of Ta, Ti and Ce, the B element is selected from Nb, and the M element includes C; The coating layer includes lithium oxide and carbide; The lithium oxide and the carbide each independently contain the A element and the B element; The carbide has oxygen vacancies.

5. The positive electrode lithium supplement according to claim 4, characterized in that: The M element also includes F; The coating layer further includes fluoride, and the fluoride contains the A element and the B element.

6. The positive electrode lithium supplement according to claim 4, characterized in that: The A element includes Ta.

7. The positive electrode lithium supplement according to any one of claims 4 to 6, characterized in that The positive electrode lithium supplement meets one or more of the following conditions: (1) The thickness of the coating layer is 1 nm to 25 nm; (3) The mass proportion of the coating layer in the positive electrode lithium supplement agent is 0.1% to 3%; (3) The median particle size of the positive electrode lithium supplement is 5 μm to 10 μm.

8. A positive electrode sheet, characterized in that: It includes a positive electrode current collector and a positive electrode active layer covering the positive electrode current collector; The positive electrode active layer includes the positive electrode lithium replenisher as claimed in any one of claims 4 to 7, or includes the positive electrode lithium replenisher prepared by the preparation method of the positive electrode lithium replenisher as claimed in any one of claims 1 to 3.

9. The positive electrode sheet according to claim 8, characterized in that: The mass proportion of the positive electrode lithium supplement in the positive electrode active layer is 1% to 10%.

10. A lithium ion battery, characterized in that: Comprising the positive electrode sheet as described in claim 8 or 9.

Images