Lithium-rich lithium cobalt oxide cathode material, preparation method, cathode sheet and application

Abstract

The application relates to a lithium-rich lithium cobalt oxide positive electrode material, which comprises an inner core and a coating layer coated on the surface of the inner core, the inner core comprises a positive electrode material matrix and a lithium supplement layer, and the lithium supplement layer is coated on the surface of the positive electrode material matrix; the lithium supplement layer comprises a material with a chemical formula of Li 1+y Co 1‑n Q n O2, wherein the Q element comprises one or more of Al, Mg, La, Y, Ti, Zr, W, Ni, Mn, Ce, Nb, Ta, Ru, Hf, V, Cr, Mo and Pd, 0.1<=y<=0.5, and 0.03<=n<=0.04. The lithium-rich lithium cobalt oxide positive electrode material has a high initial discharge specific capacity, and effectively improves the initial coulomb efficiency and reversible energy density of a secondary battery containing the lithium-rich lithium cobalt oxide positive electrode material.

Description

Technical Field

[0001] This application relates to the field of lithium secondary battery technology, and in particular to a lithium-rich lithium cobalt oxide cathode material, its preparation method, cathode sheet, and its application. Background Technology

[0002] With the rapid development of the lithium-ion battery industry, high-energy-density lithium-ion batteries are becoming increasingly popular. Therefore, developing a high-energy-density lithium cobalt oxide battery is crucial. Lithium cobalt oxide materials are characterized by high compaction density, but their low specific capacity limits the improvement of their energy density. How to improve the energy density of lithium cobalt oxide materials is an urgent problem to be solved in battery technology. Summary of the Invention

[0003] Based on this, this application provides a lithium-rich lithium cobalt oxide cathode material, a preparation method, a cathode sheet, and applications. Compared with traditional lithium cobalt oxide cathode materials, this lithium-rich lithium cobalt oxide cathode material has a higher initial discharge specific capacity, effectively improving the initial coulombic efficiency, reversible energy density, and cycle performance of secondary batteries containing this lithium-rich lithium cobalt oxide cathode material.

[0004] A first aspect of this application provides a lithium-rich lithium cobalt oxide cathode material, comprising a core and a coating layer covering the surface of the core. The core includes a cathode material substrate and a lithium replenishment layer, the lithium replenishment layer covering the surface of the cathode material substrate. The cathode material substrate comprises materials with the chemical formula Li. 1+x Co 1-m M m The O2 material, wherein the element M includes one or more of Al, Mg, La, Y, Ti, Zr, W, Ni, Mn, Ce, Nb, Ta, Ru, Hf, V, Cr, Mo, and Pd, with 0.01≤x≤0.06 and 0.03≤m≤0.04; the lithium replenishment layer includes the chemical formula Li 1+y Co 1-n Q n The material containing O2, wherein the Q element includes one or more of Al, Mg, La, Y, Ti, Zr, W, Ni, Mn, Ce, Nb, Ta, Ru, Hf, V, Cr, Mo and Pd, with 0.1≤y≤0.5 and 0.03≤n≤0.04.

[0005] In some implementations, the M element and the Q element are identical, and m = n.

[0006] In some embodiments, the coating layer includes F - and PO4 3- A compound containing at least one ion.

[0007] In some embodiments, the lithium cobalt oxide cathode material contains lithium hydroxide and lithium carbonate. The lithium hydroxide content in the lithium cobalt oxide cathode material is 10ppm-100ppm, optionally 10ppm-50ppm, and the lithium carbonate content in the lithium cobalt oxide cathode material is 10ppm-500ppm, optionally 10ppm-200ppm.

[0008] In some embodiments, the lithium content in the lithium replenishment layer gradually increases from the inner surface to the outer surface.

[0009] A second aspect of this application provides a method for preparing the lithium-rich cobalt oxide cathode material described in the first aspect of this application, comprising the following steps:

[0010] A lithium source, a cobalt source, and a compound containing element M are mixed, and the mixed material is subjected to a first sintering treatment to obtain the cathode material matrix.

[0011] The cathode material matrix and an organic lithium solvent are mixed, and the mixture is then subjected to reaction, filtration and drying to obtain the core.

[0012] The coating layer is formed on the surface of the core to obtain the lithium cobalt oxide cathode material.

[0013] In some embodiments, the lithium source includes one or more of lithium carbonate, lithium nitrate, and lithium hydroxide.

[0014] In some embodiments, the cobalt source includes one or more of cobalt tetroxide, cobalt carbonate, and cobalt hydroxide.

[0015] In some embodiments, the molar ratio of lithium in the lithium source, cobalt in the cobalt source, and total metal elements in the compound containing element M is (1.01-1.08):1:(0.03-0.04).

[0016] In some embodiments, the process conditions for the first sintering treatment include: sintering temperature of 800℃-1100℃ and sintering time of 6h-12h.

[0017] In some embodiments, the first sintering process is carried out in an atmosphere of air or oxygen.

[0018] In some embodiments, the reaction temperature is 30°C-60°C and the reaction time is 12h-24h.

[0019] In some embodiments, the organic lithium solvent includes one or more of lithium biphenyl, lithium naphthylene, lithium n-butyllithium, lithium trifluoromethanesulfonate, lithium difluorosulfonylimide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium monosulfonate 5-sulfo-1,3-phthalic acid, and lithium tetrafluoroborate.

[0020] In some embodiments, the molar ratio of the cathode material matrix to the organic lithium solvent is 1:(1.8-2.2).

[0021] In some embodiments, the step of forming the coating layer on the surface of the core to obtain the lithium-rich lithium cobalt oxide cathode material includes: combining the core with a layer containing F - and PO4 3- A compound containing at least one ion is mixed and subjected to a second sintering process.

[0022] In some embodiments, the process conditions for the second sintering treatment include: a sintering temperature of 800℃-900℃ and a sintering time of 6h-10h.

[0023] In some embodiments, the second sintering process is carried out in an atmosphere of air or oxygen.

[0024] A third aspect of this application provides a positive electrode sheet, comprising the lithium-rich cobalt oxide positive electrode material described in the first aspect of this application or the lithium-rich cobalt oxide positive electrode material prepared by the preparation method described in the second aspect of this application.

[0025] A fourth aspect of this application provides a secondary battery, including the positive electrode sheet described in the third aspect of this application.

[0026] A fifth aspect of this application provides an electrical device including the secondary battery described in the fourth aspect of this application.

[0027] Compared with traditional technologies, the above-mentioned lithium-rich cobalt oxide cathode material, preparation method, cathode sheet, and application have at least the following advantages:

[0028] Compared to traditional lithium cobalt oxide cathode materials, this lithium-rich lithium cobalt oxide cathode material, due to the presence of a lithium replenishment layer, can mitigate the severe lithium consumption problem during SEI film formation at the negative electrode. It can exhibit a higher initial specific capacity at high voltage levels, while simultaneously improving the reversible discharge specific capacity and initial coulombic efficiency of secondary batteries containing this lithium-rich lithium cobalt oxide cathode material, significantly enhancing the reversible energy density of the secondary battery. Furthermore, the coating layer prevents corrosion of the layered lithium cobalt oxide surface by corrosive substances such as electrolytes, maintaining the integrity of the lithium cobalt oxide core structure and improving the battery's cycle stability. Detailed Implementation

[0029] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, a detailed description of specific embodiments of this application is provided below. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0030] In this application, unless otherwise defined, all technical terms and jargon not explicitly stated have the same meaning as commonly understood by those skilled in the art and are common knowledge to those skilled in the art. Methods not explicitly stated are all conventional methods known to those skilled in the art. The term "multiple" in this application means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0031] In this application, terms such as "first aspect," "second aspect," and "third aspect" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, terms such as "first," "second," and "third" serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on quantity.

[0032] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0033] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0034] The initial formation of the SEI film (solid electrolyte interface film) in the negative electrode material of a secondary battery consumes Li in the positive electrode material. + Due to the Li consumed in the formation of the SEI film by the negative electrode material + It is irreversible. Secondary batteries containing lithium cobalt oxide (LCO) materials face the problem of severe lithium consumption by the anode material, especially since the introduction of silicon into the anode leads to more lithium being consumed. + loss.

[0035] To improve the energy density of secondary batteries containing lithium cobalt oxide, one approach is to focus on the battery's operating voltage and specific capacity. Currently, many researchers increase the operating voltage of lithium cobalt oxide to enhance its specific capacity, thereby improving the energy density of the secondary battery. Other researchers have improved the energy density of secondary batteries by modifying the negative electrode, increasing the compaction density and specific capacity of the graphite negative electrode (by incorporating some silicon oxide or silicon carbide). While these methods can improve the energy density of secondary batteries containing lithium cobalt oxide, the problem of low initial lithium consumption (i.e., the relatively low initial coulombic efficiency of secondary batteries containing lithium cobalt oxide) remains unresolved. Therefore, to further improve the energy density of secondary batteries containing lithium cobalt oxide, it is necessary to address the issue of low initial lithium consumption during the first charge and discharge cycle.

[0036] In view of this, one embodiment of this application provides a lithium-rich lithium cobalt oxide cathode material, which includes a core and a coating layer covering the surface of the core. The core includes a cathode material substrate and a lithium replenishment layer, the lithium replenishment layer covering the surface of the cathode material substrate; the cathode material substrate includes materials with the chemical formula Li. 1+x Co 1-m M m The O2 material, wherein element M includes one or more of Al, Mg, La, Y, Ti, Zr, W, Ni, Mn, Ce, Nb, Ta, Ru, Hf, V, Cr, Mo, and Pd, with 0.01≤x≤0.06 and 0.03≤m≤0.04; the lithium replenishment layer includes materials with the chemical formula Li 1+y Co 1-n Q n The material containing O2, wherein the Q element includes one or more of Al, Mg, La, Y, Ti, Zr, W, Ni, Mn, Ce, Nb, Ta, Ru, Hf, V, Cr, Mo and Pd, with 0.1≤y≤0.5 and 0.03≤n≤0.04.

[0037] The aforementioned lithium cobalt oxide cathode material has a layered structure. After the first charge-discharge cycle, no new impurity phases are generated, and the original layered structure is maintained. This is beneficial for the Li in the secondary battery. + The transmission is unaffected. Compared with traditional lithium cobalt oxide cathode materials, the above-mentioned lithium-rich lithium cobalt oxide cathode material can achieve a higher initial specific capacity at the same voltage platform. Meanwhile, this lithium-rich lithium cobalt oxide cathode material increases Li... + The content of which has excess Li + This method, which supplies power to the negative electrode, can mitigate the problem of severe lithium consumption during SEI film formation at the negative electrode and will not cause lithium loss in the bulk phase of the positive electrode material matrix. +This reduces energy loss, thereby improving the reversible capacity and initial coulombic efficiency of secondary batteries containing this lithium-rich lithium cobalt oxide cathode material, and significantly enhancing the reversible energy density of the secondary battery. Furthermore, the coating layer prevents corrosion of the layered lithium cobalt oxide surface by corrosive substances such as the electrolyte, maintaining the integrity of the lithium cobalt oxide core structure and improving the battery's cycle stability. The M element doped in the cathode material matrix and the Q element doped in the lithium replenishment layer play a role in stabilizing the structure. The coating layer on the core surface enhances interfacial stability and prevents side reactions between the core and the electrolyte. It is understood that x includes, but is not limited to: 0.01, 0.02, 0.03, 0.04, 0.05, 0.06; m includes, but is not limited to: 0.03, 0.031, 0.032, 0.033, 0.034, 0.035, 0.036, 0.037, 0.038, 0.039, 0.04; y includes, but is not limited to: 0.1, 0.13, 0.15, 0.18, 0.2, 0.23, 0.25, 0.28, 0.3, 0.35, 0.4, 0.45, 0.5; n includes, but is not limited to: 0.03, 0.031, 0.032, 0.033, 0.034, 0.035, 0.036, 0.037, 0.038, 0.039, 0.04.

[0038] In some implementations, the M and Q elements are identical, and m = n. Therefore, the materials of the cathode substrate and the lithium replenishment layer are structurally more similar, improving the reversible capacity of the lithium cobalt oxide cathode material without affecting its stability, thus further enhancing the cycle performance of the lithium cobalt oxide cathode material. It can be understood that the identical M and Q elements, and m = n, refer to Li... 1+x Co 1-m M m O2 and Li 1+y Co 1-n Q n Compared to O2, only the molar number of lithium elements differs. For example, the cathode material matrix includes materials with the chemical formula Li. 1.02 Co 0.97 Al 0.03 O2 materials, lithium replenishment layer including Li 1.1 Co 0.97 Al 0.03 O2 materials; or cathode material matrix including materials with the chemical formula Li 1.04 Co 0.96 Al 0.02 Mg 0.02 O2 materials, lithium replenishment layer including Li 1.2 Co 0.96 Al 0.02 Mg 0.02O2 materials; or cathode material matrix including materials with the chemical formula Li 1.0 6Co 0.96 Al 0.02 Mg 0.01 La 0.01 O2 materials, lithium replenishment layer including Li 1.3 Co 0.96 Al 0.02 Mg 0.01 La 0.01 Materials containing O2.

[0039] In some embodiments, the coating layer includes F - and PO4 3- A compound containing at least one ion. The coating layer contains F... - and PO4 3- Compounds containing at least one ion can prevent side reactions between the core and the electrolyte, thereby improving the cycle performance of lithium-rich cobalt oxide cathode materials. Optionally, compounds containing F - and PO4 3- Compounds containing at least one of the following ions include, but are not limited to, one or more of AlF3, AlPO4, LiF, and Li3PO4.

[0040] In some embodiments, the lithium-rich lithium cobalt oxide cathode material contains lithium hydroxide and lithium carbonate. The lithium hydroxide content in the lithium-rich lithium cobalt oxide cathode material is 10ppm-100ppm, and the lithium carbonate content is 10ppm-500ppm. Compared with conventional lithium cobalt oxide cathode materials, the lithium hydroxide and lithium carbonate contents in the above-mentioned lithium-rich lithium cobalt oxide cathode material are significantly reduced, and it exhibits better stability in air. It is understood that the lithium hydroxide content in the lithium-rich lithium cobalt oxide cathode material includes, but is not limited to: 10ppm, 30ppm, 50ppm, 70ppm, and 100ppm; and the lithium carbonate content in the lithium-rich lithium cobalt oxide cathode material includes, but is not limited to: 10ppm, 30ppm, 50ppm, 100ppm, 200ppm, 300ppm, 400ppm, and 500ppm. Furthermore, the lithium hydroxide content in the lithium cobalt oxide cathode material is 10ppm-50ppm, and the lithium carbonate content in the lithium cobalt oxide cathode material is 10ppm-200ppm.

[0041] In some implementations, the lithium content in the lithium replenishment layer gradually increases from the inner surface to the outer surface.

[0042] In some embodiments, the lithium content in the lithium replenishment layer is higher than the lithium content in the cathode material matrix. Therefore, the aforementioned lithium replenishment layer can provide excess Li... + Supplying the negative electrode with Li will not cause Li in the bulk phase of the positive electrode material matrix.+ This reduces losses, thereby further improving the reversible capacity and first coulombic efficiency of secondary batteries containing this lithium-rich cobalt oxide cathode material, and greatly enhancing the reversible energy density of the secondary battery.

[0043] Another embodiment of this application provides a method for preparing the above-mentioned lithium-rich cobalt oxide cathode material, comprising the following steps:

[0044] A lithium source, a cobalt source, and a compound containing element M are mixed, and the mixed material is subjected to a first sintering treatment to obtain a cathode material matrix.

[0045] The cathode material matrix and organic lithium solvent are mixed, and the mixture is subjected to reaction, filtration and drying to obtain the core.

[0046] A coating layer is formed on the surface of the core to obtain lithium-rich cobalt oxide cathode material.

[0047] In the above preparation method, an organic lithium solvent forms a lithium replenishment layer on the surface of the cathode material matrix through chemical pre-lithiation. The above method for preparing lithium-rich lithium cobalt oxide cathode materials is an integrated synthesis technique. The prepared lithium-rich lithium cobalt oxide cathode material is more stable than traditional lithium cobalt oxide cathode materials, solving problems such as the introduction of impurity phases in the cathode formulation system, avoiding interference from impurities during lithium ion transport at the positive and negative electrodes, and resolving the issues of unstable cathode lithium replenishment agents and processing difficulties. The above method for preparing lithium-rich lithium cobalt oxide cathode materials is relatively simple and easy to scale up for production.

[0048] Furthermore, the aforementioned lithium-rich cobalt oxide cathode material possesses a layered structure, and after the first charge-discharge cycle, no new impurity phases are generated, maintaining its original layered structure. This is beneficial for the Li content in the secondary battery. + The transmission is unaffected. Compared with traditional lithium cobalt oxide cathode materials, the lithium-rich lithium cobalt oxide cathode material prepared by the above method can exhibit a higher initial specific capacity at the same voltage platform. Simultaneously, this lithium-rich lithium cobalt oxide cathode material increases the Li... + The content of which has excess Li + This method, which supplies power to the negative electrode, can mitigate the problem of severe lithium consumption during SEI film formation at the negative electrode and will not cause lithium loss in the bulk phase of the positive electrode material matrix. + This reduces energy loss, thereby improving the reversible capacity and initial coulombic efficiency of secondary batteries containing this lithium-rich lithium cobalt oxide cathode material, and significantly enhancing the reversible energy density of the secondary battery. Furthermore, the coating layer prevents corrosion of the layered lithium cobalt oxide surface by corrosive substances such as the electrolyte, maintaining the integrity of the lithium cobalt oxide core structure and improving the battery's cycle stability. The M element doped in the cathode material matrix and the Q element doped in the lithium replenishment layer play a role in stabilizing the structure. The coating layer on the core surface enhances interfacial stability and prevents side reactions between the core and the electrolyte.

[0049] In some implementations, the lithium source includes one or more of lithium carbonate, lithium nitrate, and lithium hydroxide.

[0050] In some embodiments, the cobalt source includes one or more of cobalt tetroxide, cobalt carbonate, and cobalt hydroxide.

[0051] In some embodiments, the molar ratio of lithium in the lithium source, cobalt in the cobalt source, and the total metal element in the compound containing element M is (1.01-1.08):1:(0.03-0.04). It is understood that the molar ratio of lithium in the lithium source, cobalt in the cobalt source, and the total metal element in the compound containing element M includes, but is not limited to: 1.01:1:0.03, 1.02:1:0.03, 1.03:1:0.032, 1.04:1:0.034, 1.06:1:0.036, 1.07:1:0.038, and 1.08:1:0.04. Optionally, the compound containing element M includes, but is not limited to, oxides containing element M, such as Al2O3, MgO, La2O3, Y2O3, ZrO2, etc.

[0052] In some embodiments, the process conditions for the first sintering treatment include: a sintering temperature of 800℃-1100℃ and a sintering time of 6h-12h. It is understood that the above sintering temperatures include, but are not limited to: 800℃, 850℃, 900℃, 950℃, 1000℃, 1020℃, 1040℃, 1060℃, 1080℃, and 1100℃; and the above sintering times include, but are not limited to: 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h, 10h, 11h, and 12h.

[0053] In some embodiments, the first sintering process is carried out in an atmosphere of air or oxygen.

[0054] In some embodiments, the organic lithium solvent includes one or more of lithium biphenyl, lithium naphthylene, lithium n-butyllithium, lithium trifluoromethanesulfonate, lithium difluorosulfonylimide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium monosulfonate 5-sulfo-1,3-phthalic acid, and lithium tetrafluoroborate. These types of organic lithium solvents are readily available, which is beneficial for the large-scale production of lithium-rich cobalt oxide cathode materials.

[0055] In some embodiments, the molar ratio of the cathode material matrix to the organic lithium solvent is 1:(1.8-2.2). It is understood that the molar ratio of the cathode material matrix to the organic lithium solvent includes, but is not limited to: 1:1.8, 1:1.9, 1:2, 1:2.1, and 1:2.2.

[0056] In some embodiments, the step of forming a coating layer on the surface of the core to obtain a lithium-rich lithium cobalt oxide cathode material includes: combining the core with a coating layer containing F.- and PO4 3- A compound containing at least one ion is mixed and subjected to a second sintering process.

[0057] In some embodiments, the process conditions for the second sintering treatment include: a sintering temperature of 800℃-900℃ and a sintering time of 6h-10h.

[0058] In some embodiments, the second sintering process is carried out in an atmosphere of air or oxygen.

[0059] Another embodiment of this application provides a positive electrode sheet, comprising the above-described lithium cobalt oxide positive electrode material or the lithium cobalt oxide positive electrode material prepared by the above-described preparation method.

[0060] The aforementioned positive electrode sheet comprises a positive current collector and an active material layer located on at least one side of the positive current collector. The active material layer includes a positive active material, a conductive agent, and a binder. The positive active material includes the aforementioned lithium-rich cobalt oxide positive electrode material or the lithium-rich cobalt oxide positive electrode material prepared by the aforementioned preparation method. The conductive agent and binder can be commonly used in this technical field.

[0061] Another embodiment of this application provides a secondary battery including the above-described positive electrode.

[0062] The aforementioned secondary battery may include, for example, the positive electrode, negative electrode, electrolyte, and separator described above. The separator is disposed between the positive and negative electrodes, primarily serving to prevent short circuits between the positive and negative electrodes while allowing ions to pass through. The electrolyte, located between the positive and negative electrodes, acts as a conductor of ions. During the charging and discharging process of the secondary battery, lithium ions repeatedly insert and extract between the positive and negative electrodes. This application does not impose any particular limitations on the negative electrode, electrolyte, and separator; the negative electrode, electrolyte, and separator can be prepared using methods commonly used in this technical field, or other commonly used methods in this field. Exemplarily, the negative electrode active material in the negative electrode may include one or more of the following: artificial graphite, natural graphite, hard carbon, soft carbon, elemental silicon, silicon oxides, silicon-carbon compounds, silicon-nitrogen compounds, silicon alloys, and tin-based materials.

[0063] Another embodiment of this application provides an electrical device including the aforementioned secondary battery.

[0064] The aforementioned electrical devices may include any equipment or device powered by a secondary battery, such as mobile phones, laptops, electric vehicles, ships, satellites, energy storage devices, smart home appliances, etc., but are not limited thereto.

[0065] To further illustrate this application, the technical solution of this application is described in detail below with reference to specific embodiments. Where specific techniques or conditions are not specified in the embodiments, they are performed in accordance with 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.

[0066] Example 1

[0067] A method for preparing high-energy-density lithium-rich cobalt oxide batteries includes the following steps:

[0068] (1) A first sintering process is performed on a mixture of cobalt tetroxide precursor (Co3O4), lithium salt (Li2CO3), and a first compound (Al2O3, MgO, La2O3, Y2O3) to obtain a lithium cobalt oxide matrix (cathode material matrix), the chemical formula of which is Li. 1.02 Co 0.962 Al 0.03 Mg 0.005 La 0.001 Y 0.002 O2; the molar ratio of lithium in lithium carbonate to cobalt in cobalt tetroxide (Li / Co) is 1.06; the molar ratio of total metal elements in the first compound to cobalt in cobalt tetroxide is 0.039:1; the first calcination treatment is carried out in an air atmosphere, and the process conditions for the first calcination treatment include: calcination temperature 1060℃, holding time 6.5h;

[0069] (2) The lithium cobalt oxide matrix and the organic lithium solvent (lithium biphenyl) are mixed evenly at a lithium molar ratio of 1:2 and reacted in a tank at 60°C for 12 hours. After filtration and drying, a lithium-rich lithium cobalt oxide semi-finished product (core) is obtained; the chemical formula of the lithium replenishment layer in the lithium-rich lithium cobalt oxide semi-finished product is Li 1.5 Co 0.962 Al 0.03 Mg 0.005 La 0.001 Y 0.002 O2, the mass of the lithium replenishment layer accounts for 10% of the mass of the cathode material matrix;

[0070] (3) Mix the lithium cobalt oxide semi-finished product and the second compound (LiF, AlPO4) evenly, and then carry out the second sintering treatment. The process conditions of the second sintering treatment include: sintering temperature 870℃, sintering time 8h; after mechanical crushing, lithium cobalt oxide cathode material with lithium gradient structure is obtained.

[0071] (4) The positive electrode material, polyvinylidene fluoride (PVDF), N-methylpyrrolidone (NMP) and acetylene black are mixed evenly in a certain proportion to prepare a mixed positive electrode slurry with a certain fluidity. The negative electrode material, binder LA133 and carbon nanotubes (CNT) are mixed evenly in a certain proportion to prepare a mixed negative electrode slurry with a certain fluidity. The positive and negative electrode slurries are then processed through coating-rolling-slicing-winding-assembly-liquid injection-formation-second sealing-capacity testing and other processes to prepare the finished soft-pack battery. The positive electrode material is lithium cobalt oxide positive electrode material, and the mass ratio of positive electrode material, PVDF and acetylene black is 90:6:4. The negative electrode material is graphite, and the mass ratio of graphite, LA133 and CNT is 92:6:2.

[0072] Example 2

[0073] A method for preparing high-energy-density lithium-rich cobalt oxide batteries includes the following steps:

[0074] (1) A mixture of cobalt tetroxide precursor (Co3O4), lithium salt (Li2CO3), and a first compound (Al2O3, MgO, La2O3) is subjected to a first calcination treatment to obtain lithium cobalt oxide matrix (cathode material matrix), the chemical formula of which is Li. 1.015 Co 0.962 Al 0.03 Mg 0.005 La 0.003 O2; the molar ratio of lithium in lithium carbonate to cobalt in cobalt tetroxide (Li / Co) is 1.06; the molar ratio of total metal elements in the first compound to cobalt in cobalt tetroxide is 0.039:1; the first calcination treatment is carried out in an air atmosphere, and the process conditions for the first calcination treatment include: calcination temperature 1050℃, holding time 8h;

[0075] (2) The lithium cobalt oxide matrix and the organic lithium solvent (n-butyllithium) are mixed evenly at a lithium molar ratio of 1:2 and reacted in a tank at 60°C for 12 hours. After filtration and drying, a lithium-rich lithium cobalt oxide semi-finished product (core) is obtained; the chemical formula of the lithium replenishment layer in the lithium-rich lithium cobalt oxide semi-finished product is Li 1.5 Co 0.962 Al 0.03 Mg 0.005 La 0.003 O2, the mass of the lithium supplement layer accounts for 10% of the mass of the lithium cobalt oxide matrix;

[0076] (3) The lithium-rich cobalt oxide semi-finished product and the second compound (LiF, LATP (Li 1.3 Al 0.3 Ti 1.7(PO4)3)) are mixed evenly, and then a second sintering treatment is carried out. The process conditions for the second sintering treatment include: sintering temperature 870℃, sintering time 8h; after mechanical crushing, lithium-rich cobalt oxide cathode material with lithium gradient structure is obtained.

[0077] (4) The positive electrode material, PVDF, NMP and acetylene black are mixed evenly in a certain proportion to prepare a mixed positive electrode slurry with a certain fluidity. The negative electrode material, LA133 and CNT are mixed evenly in a certain proportion to prepare a mixed negative electrode slurry with a certain fluidity. The positive and negative electrode slurries are then processed through coating-rolling-slicing-winding-assembly-liquid injection-formation-second sealing-capacity testing and other processes to prepare the finished soft-pack battery. The positive electrode material is lithium cobalt oxide positive electrode material, and the mass ratio of positive electrode material, PVDF and acetylene black is 90:6:4. The negative electrode material is a mixture of graphite material and silicon oxide material (SiO2) with a mass ratio of 95:5. The mass ratio of negative electrode material, LA133 and CNT is 92:6:2.

[0078] Example 3

[0079] The process is basically the same as in Example 1, except that: in step (1), the molar ratio of lithium in lithium carbonate to cobalt in cobalt tetroxide (Li / Co) is 1.07; and the chemical formula of the matrix lithium cobalt oxide obtained in step (1) is Li 1.025 Co 0.962 Al 0.03 Mg 0.005 La 0.001 Y 0.002 O2, the chemical formula of the lithium replenishment layer in the lithium-rich cobalt oxide semi-finished product obtained in step (2) is Li 1.5 Co 0.962 Al 0.03 Mg 0.005 La 0.001 Y 0.002 O2, the mass of the lithium supplement layer accounts for 10% of the mass of the lithium cobalt oxide matrix.

[0080] Comparative Example 1 (no lithium replenishment layer and no coating layer)

[0081] The process is basically the same as in Example 1, except that steps (2) and (3) are omitted, and the positive electrode material in step (4) is replaced with the matrix lithium cobalt oxide prepared in step (1).

[0082] Comparative Example 2 (without lithium replenishment layer)

[0083] The process is basically the same as in Example 1, except that step (2) is omitted and the lithium-rich cobalt oxide semi-finished product in step (3) is replaced with the matrix lithium cobalt oxide prepared in step (1).

[0084] Comparative Example 3 (without coating layer)

[0085] The process is basically the same as in Example 1, except that step (3) is omitted and the positive electrode material in step (4) is replaced with the lithium-rich cobalt oxide semi-finished product prepared in step (2).

[0086] Comparative Example 4 (Lithium cobalt oxide matrix and lithium supplement agent are directly mixed)

[0087] The process is basically the same as in Example 1, except that steps (2) and (3) are omitted, and the positive electrode material in step (4) is replaced with a mixture of lithium cobalt oxide matrix and lithium replenishing agent prepared in step (1). The lithium replenishing agent is Li6CoO4, and the amount of lithium replenishing agent added is 1% of the mass of the lithium cobalt oxide matrix material.

[0088] Comparative Example 5 (direct mixing of matrix lithium cobalt oxide and lithium supplement agent)

[0089] The process is basically the same as in Example 2, except that steps (2) and (3) are omitted, and the positive electrode material in step (4) is replaced with a mixture of lithium cobalt oxide matrix and lithium replenishing agent prepared in step (1). The lithium replenishing agent is Li6CoO4, and the amount of lithium replenishing agent added is 1% of the mass of the lithium cobalt oxide matrix material.

[0090] The composition of the cathode material matrix and lithium replenishment layer prepared in each embodiment and comparative example was determined using an ICP-AES analyzer.

[0091] The residual alkali content in the products prepared in Examples 1-3 and Comparative Examples 1-4 was tested. The test method for residual alkali content was as follows: A mass of positive electrode material was placed in a beaker and 100 mL of deionized water was added. The mixture was stirred in a sealed container at room temperature for 30 minutes. The mixture was then filtered to obtain a clear liquid. The clear liquid was subjected to acid-base titration using a potentiometric titration device. The concentration of hydrochloric acid was C1, and the volume of the clear liquid was V. The volume of hydrochloric acid consumed at the first jump point was V1, and the volume of hydrochloric acid consumed at the second jump point was V2. The LiOH (wt%) was calculated as (V2-V1)*23.95*C1 / A / V, and the Li2CO3 (wt%) was calculated as V2*73.89*C1 / A / V. The content of LiOH and Li2CO3 in the product was thus obtained. The test results are shown in Table 1.

[0092] Table 1

[0093]

[0094]

[0095] As can be seen from Table 1, compared with Comparative Example 1 and Comparative Examples 3-5, the content of LiOH and Li2CO3 of the lithium-rich cobalt oxide prepared in Examples 1-3 did not change much before and after placement, indicating that the lithium-rich cobalt oxide prepared in Examples 1-3 has good stability in air.

[0096] Electrochemical performance testing

[0097] Test methods for first charge specific capacity and first discharge specific capacity: Under 25℃ conditions, the soft pack battery is charged at 0.1C and discharged at 0.1C, with a voltage range of 3V-4.53V.

[0098] Test methods for capacity retention and energy density: Under 45℃ conditions, the pouch battery is charged at 0.5C, and the 0.5C charge-discharge test cycle is 500 cycles, with a voltage range of 3V-4.53V; the capacity retention rate of the Xth week = (discharge specific capacity of the Xth week / discharge specific capacity of the 1st week) × 100%, where X = 100, 200, 300, 400 or 500; the energy density of the pouch battery = (discharge capacity × average voltage) / mass of the pouch battery, where the unit of discharge capacity is mAh, and the average voltage is the average voltage of the pouch battery throughout the entire discharge process.

[0099] Table 2

[0100]

[0101] As shown in Table 2, the lithium-rich cobalt oxide cathode material provided in this application exhibits an initial charge-discharge specific capacity higher than 209.9 mAh / g when applied in lithium-ion batteries, while the initial charge-discharge specific capacities of Comparative Examples 1 to 5 are all lower. This indicates that coating the cathode material substrate with a lithium replenishment layer can mitigate the severe lithium consumption problem during SEI film formation in the anode, resulting in a higher initial specific capacity under the same high-voltage platform. Simultaneously, it improves the initial coulombic efficiency of the secondary battery containing this lithium-rich cobalt oxide cathode material. Furthermore, due to the lithium replenishment layer and the presence of F... - and PO4 3- The presence of the compound coating layer resulted in good cycling performance in Examples 1-3, with a capacity retention rate exceeding 90.14% after 500 cycles. Furthermore, compared to Comparative Examples 1-5, the batteries in Examples 1-3 exhibited higher energy density after 500 cycles.

[0102] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above 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.

[0103] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A lithium-rich lithium cobalt oxide cathode material, characterized in that, The electrode comprises a core and a coating layer covering the surface of the core. The core includes a positive electrode material substrate and a lithium replenishment layer. The lithium replenishment layer is coated on the surface of the positive electrode material substrate. The positive electrode material substrate and an organic lithium solvent are chemically pre-lithiated to form the lithium replenishment layer on the surface of the positive electrode material substrate. The positive electrode material substrate comprises a material with the chemical formula Li. 1+x Co 1-m M m The O2 material, wherein the element M includes one or more of Al, Mg, La, Y, Ti, Zr, W, Ni, Mn, Ce, Nb, Ta, Ru, Hf, V, Cr, Mo, and Pd, with 0.01≤x≤0.06 and 0.03≤m≤0.04; the lithium replenishment layer includes the chemical formula Li 1+y Co 1-n Q n The material containing O2, wherein the Q element includes one or more of Al, Mg, La, Y, Ti, Zr, W, Ni, Mn, Ce, Nb, Ta, Ru, Hf, V, Cr, Mo and Pd, with 0.1≤y≤0.5 and 0.03≤n≤0.

04.

2. The lithium-rich cobalt oxide cathode material according to claim 1, characterized in that, The M element and the Q element are exactly the same, and m=n.

3. The lithium-rich cobalt oxide cathode material according to claim 1 or 2, characterized in that, The coating layer includes F - and PO4 3- A compound containing at least one ion.

4. The lithium-rich cobalt oxide cathode material according to claim 1 or 2, characterized in that, The lithium-rich cobalt oxide cathode material possesses at least one of the following characteristics: (1a) The lithium cobalt oxide cathode material contains lithium hydroxide and lithium carbonate, wherein the lithium hydroxide content in the lithium cobalt oxide cathode material is 10ppm-100ppm and the lithium carbonate content in the lithium cobalt oxide cathode material is 10ppm-500ppm. (1b) The lithium content in the lithium replenishment layer gradually increases from the inner surface to the outer surface.

5. The lithium-rich cobalt oxide cathode material according to claim 4, characterized in that, The lithium hydroxide content in the lithium cobalt oxide cathode material is 10ppm-50ppm.

6. The lithium-rich cobalt oxide cathode material according to claim 4, characterized in that, The lithium carbonate content in the lithium cobalt oxide cathode material is 10ppm-200ppm.

7. The method for preparing the lithium-rich cobalt oxide cathode material according to any one of claims 1-6, characterized in that, Includes the following steps: A lithium source, a cobalt source, and a compound containing element M are mixed, and the mixed material is subjected to a first sintering treatment to obtain the cathode material matrix. The cathode material matrix and the organic lithium solvent are mixed, and the mixture is subjected to reaction, filtration and drying to obtain the core; the reaction temperature is 30℃-60℃. The coating layer is formed on the surface of the core to obtain the lithium cobalt oxide cathode material.

8. The preparation method according to claim 7, characterized in that, The preparation method of the lithium-rich cobalt oxide cathode material satisfies at least one of the following conditions: (2a) The lithium source includes one or more of lithium carbonate, lithium nitrate and lithium hydroxide; (2b) The cobalt source includes one or more of cobalt tetroxide, cobalt carbonate, and cobalt hydroxide; (2c) The molar ratio of lithium in the lithium source, cobalt in the cobalt source, and total metal elements in the compound containing element M is (1.01-1.08): 1:(0.03-0.04); (2d) The process conditions for the first sintering treatment include: sintering temperature of 800℃-1100℃ and sintering time of 6h-12h. (2e) The first sintering process is carried out in an atmosphere of air or oxygen; (2f) The reaction time is 12h-24h.

9. The preparation method according to claim 7 or 8, characterized in that, The organolithium solvent satisfies at least one of the following conditions: (3a) The organic lithium solvent includes one or more of the following: lithium biphenyl, lithium naphthylene, lithium n-butyl, lithium trifluoromethanesulfonate, lithium difluorosulfonylimide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorooxalate borate, lithium mono-5-sulfon-1,3-phthalic acid, and lithium tetrafluoroborate. (3b) The molar ratio of the cathode material matrix to the organic lithium solvent is 1:(1.8-2.2).

10. The preparation method according to claim 7, characterized in that, The step of forming the coating layer on the surface of the core to obtain the lithium-rich cobalt oxide cathode material includes: combining the core with a coating containing F... - and PO4 3- A compound containing at least one ion is mixed and subjected to a second sintering process.

11. The preparation method according to claim 10, characterized in that, The process conditions for the second sintering treatment include: sintering temperature of 800℃-900℃ and sintering time of 6h-10h.

12. The preparation method according to claim 10, characterized in that, The second sintering process is carried out in an atmosphere of air or oxygen.

13. A positive electrode plate, characterized in that, This includes the lithium-rich cobalt oxide cathode material according to any one of claims 1-6 or the lithium-rich cobalt oxide cathode material prepared by the preparation method according to any one of claims 7-12.

14. A secondary battery, characterized in that, Includes the positive electrode sheet as described in claim 13.

15. An electrical appliance, characterized in that, Includes the secondary battery as described in claim 14.

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