O2-type lithium-rich manganese-based positive electrode material and synthesis and application thereof

Abstract

The present invention belongs to the technical field of lithium-ion batteries, and more specifically relates to an O2-type lithium-rich manganese-based cathode material and its synthesis and application. The present invention provides an O2-type lithium-rich manganese-based cathode material with the chemical formula Li x [Li y Mn z Ni u Co v O2, where 0.6 < x ≤ 0.9, 0.1 ≤ y ≤ 0.3, 0.6 ≤ z ≤ 0.7, 0.15 ≤ u ≤ 0.25, 0 ≤ v ≤ 0.13; it has an O2-type layered structure, the local oxygen atom stacking mode is ABAC, the Li layer and the transition metal layer are alternately arranged, and the layers are connected by oxygen atoms. It is prepared by ion exchange of a P2-type sodium-lithium nickel manganese-based layered oxide with a specific Ni / Mn stoichiometric ratio and a lithium salt. The Jahn-Teller effect generated by Ni 3+ causes lattice distortion, enhances the strength of the Ni-O bond, the lattice structure of the O2 phase inhibits the migration of transition metal atoms during cycling, prevents the loss of oxygen during cycling, and greatly alleviates voltage decay. The average voltage decay of this material is 0.64 mV / cycle in the first 100 cycles at 80 mAh / g, and the capacity retention rate can reach 94% after 100 cycles.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery technology, and more specifically relates to an O2-type lithium-rich manganese-based cathode material and its synthesis and application. Background Technology

[0002] Developing renewable energy is an inevitable choice to replace traditional fossil fuels. Renewable energy power generation is affected by the natural environment, resulting in large power fluctuations. Direct grid connection disrupts the power grid, necessitating large-scale energy storage devices for stable grid connection. The widespread adoption of electric vehicles also promotes the development of high-energy-density, environmentally friendly, and safe batteries. Lithium-ion batteries have applications in both energy storage and power applications, but their energy density is limited. Cathode materials are key to improving energy density, and the development of high-nickel or lithium-rich manganese-based cathode materials is a research focus.

[0003] In lithium-ion battery cathode material systems, lithium-rich manganese-based layered oxides (chemical formula Li[Li]) are preferred. x TM y Lithium-rich manganese-based cathode materials (Li2MnO3 phase with C2 / m space group and LiTMO2 phase with R3̅m space group, where TM is a transition metal such as Ni, Co, or Mn) have become a research hotspot due to their high specific capacity, low cost, and high energy density. These materials are composite structures formed at the nanoscale by the co-existence of the Li2MnO3 phase with the LiTMO2 phase with the LiTMO2 phase with the R3̅m space group (where TM is a transition metal such as Ni, Co, or Mn). The general formula can be expressed as xLi2MnO3·(1-x)LiTMO2. The unique Li–O–Li configuration in the Li2MnO3 phase can form O 2p non-bonding orbitals, stimulating the redox activity of lattice oxygen and thus providing additional capacity. However, in practical applications, they still face serious voltage decay and lattice oxygen loss problems, severely restricting their commercialization. Summary of the Invention

[0004] The purpose of this invention is to provide an O2-type lithium-rich manganese-based cathode material and its synthesis and application, and more specifically, to provide a micron-scale metastable phase lithium-rich manganese-based cathode material to solve the problems existing in the prior art, reduce lattice collapse and oxygen loss in the material during cycling, and improve rate performance and cycle stability.

[0005] To achieve the above objectives, the present invention provides the following solution: One of the technical solutions of this invention is to provide an O2-type lithium-rich manganese-based cathode material, wherein the chemical formula of the O2-type lithium-rich manganese-based cathode material is Li. x [Li y Mn z Ni u Co v O2, of which 0.6 <x≤0.9,0.1≤y≤0.3,0.6≤z≤0.7,0.15≤u≤0.25,0≤v≤0.13。

[0006] The O2-type lithium-rich manganese-based cathode material provided by this invention, through the design of specific element ratios, utilizes the presence of Ni based on charge conservation. 3+ The chemical state of Ni induces 3+ They migrate to the lithium layer as pillar atoms through the Jahn-Teller effect.

[0007] Furthermore, the O2-type lithium-rich manganese-based cathode material has an O2-type layered structure with local oxygen atom stacking in an ABAC pattern. Li layers and transition metal layers are arranged alternately, and the layers are connected by oxygen atoms.

[0008] Furthermore, the O2-type lithium-rich manganese-based cathode material has a thickness of 2-10 μm and a width of 2-15 μm, and has a layered crystal structure.

[0009] The O2-type lithium-rich manganese-based cathode material provided by this invention has an O2-type phase structure, consisting of Li2MnO3 phase of space group C2 / m and / or LiTMO2 of space group R3̅m (TM is a transition metal such as Ni, Co, Mn, etc.), and some Ni elements in the material have a valence state of +3.

[0010] The O2-type lattice structure of O2-type lithium-rich manganese-based cathode materials increases the migration energy of transition metal atoms, Ni 3+ The Jahn-Teller effect enhances the strength of the Ni-O bond, suppressing the irreversible migration of transition metal atoms and the loss of lattice oxygen during cycling.

[0011] The second technical solution of the present invention provides a method for preparing the above-mentioned O2-type lithium-rich manganese-based cathode material, the steps of which include: Transition metal salt precursors were prepared by co-precipitation treatment using nickel, manganese, cobalt and aluminum sources as reactants. The transition metal salt precursor was mixed evenly with a sodium source and a first lithium source, and then ground and calcined to obtain a layered sodium oxide material. The layered sodium oxide is subjected to ion exchange treatment with a second lithium source to obtain the O2-type lithium-rich manganese-based cathode material (micron-scale metastable phase lithium-rich manganese-based cathode material).

[0012] Furthermore, the co-precipitation treatment step includes: The nickel, manganese, cobalt and aluminum sources were prepared into a mixed salt solution of transition metals. The solution was mixed evenly with a complexing agent under an inert atmosphere. The pH of the system was adjusted to 8-10. A precipitant was added under stirring to carry out a co-precipitation reaction. After the reaction was completed, the solution was aged, centrifuged and dried to obtain the transition metal salt precursor.

[0013] Optionally, the nickel source is at least one of nickel sulfate, acetate and nitrate.

[0014] Optionally, the manganese source is at least one of manganese sulfate, acetate and nitrate.

[0015] Optionally, the cobalt source is at least one of cobalt sulfate, acetate and nitrate.

[0016] Optionally, the aluminum source is at least one of aluminum sulfate, acetate and nitrate.

[0017] Optionally, the molar concentration of the transition metal mixed salt solution is 1-2 mol·L⁻¹. -1 .

[0018] Optionally, the complexing agent is added in solution form, including citric acid solution and / or ethylene glycol solution, with a molar concentration of 0.1-1 mol·L⁻¹. -1 .

[0019] Optionally, the pH value of the adjustment system is 8-10, which is the pH value adjusted by a pH adjuster solution.

[0020] Preferably, the pH adjusting agent solution comprises an aqueous ammonia solution and / or an ammonium bicarbonate solution, with a molar concentration of 1-2 mol·L⁻¹. -1 .

[0021] Optionally, the precipitant is added in solution form, including sodium carbonate solution and / or sodium hydroxide solution, with a molar concentration of 1.5-2.5 mol·L⁻¹. -1 .

[0022] Optionally, the molar ratio of the metal salt and the complexing agent in the transition metal mixed salt solution is 5-10.

[0023] Optionally, the molar ratio of the metal salt to the precipitant in the transition metal mixed salt solution is 1:(1~1.3).

[0024] Optionally, the stirring speed of the coprecipitation reaction is 500-1500 rpm, the temperature is 40-85℃, and the time is 6-12 h.

[0025] Furthermore, the preparation steps of the layered sodium oxide material include: The transition metal salt precursor is mixed and homogenized with the first lithium source and sodium source, then ground. Under air atmosphere, the temperature is increased to 400-500℃ at a heating rate of 3-6℃ / min and held for 4-6 hours. Then, the temperature is increased to 800-900℃ at a heating rate of 3-8℃ / min and held for 15-20 hours. After cooling, the sodium layered oxide is obtained.

[0026] Optionally, the first lithium source and sodium source are configured according to the chemical formula Na x [Li yMn z Ni u Co v O2 or Li x [Li y Mn z Ni u Co v Prepare O2 according to the stoichiometric ratio shown, or prepare it in excess of 1-10% according to the stoichiometric ratio shown.

[0027] Optionally, the sodium source includes at least one of sodium carbonate, sodium acetate, sodium fluoride, sodium nitrate, and sodium hydroxide.

[0028] Optionally, the first lithium source includes at least one of lithium carbonate, lithium hydroxide, and lithium oxalate.

[0029] In the preparation of layered sodium oxide materials, the pre-calcination stage (400-500℃) is beneficial for promoting the pre-reaction of raw materials, eliminating impurities (such as water of crystallization or organic matter), promoting the decomposition of precursors and the initial intercalation of lithium and sodium, and initially forming the crystal lattice structure of transition metal oxides, providing a structural basis for subsequent high-temperature crystallization. The role of high-temperature treatment (800-900℃) is to promote the formation and stabilization of the crystal structure through specific high-temperature treatment, regulate the valence of transition metals, and form thermodynamically stable P2-type layered sodium oxides.

[0030] Furthermore, the ion exchange treatment step includes: Sodium layered oxide and a second lithium source undergo an ion exchange reaction at 250-400℃ for 3-10 hours. After the reaction is completed, the material is washed, filtered, and dried to obtain the O2-type lithium-rich manganese-based cathode material.

[0031] Optionally, the second lithium source includes at least one of lithium chloride, lithium hydroxide, lithium carbonate, lithium acetate, lithium oxalate, lithium nitrate, lithium oxide, and lithium peroxide.

[0032] Optionally, the molar ratio of the second lithium source to the sodium layered oxide is 5-10:1. The molar amount of the sodium layered oxide is expressed in terms of the molar amount of Na atoms.

[0033] This invention utilizes a co-precipitation method to prepare transition metal salt precursors; calcination with sodium and lithium sources to obtain sodium-lithium-nickel-manganese layered oxides (sodium layered oxides); and ion exchange with lithium salts to prepare an O2-type layered structure that achieves shared lines between LiO6 octahedra and TMO6 octahedra. Furthermore, this preparation method is simple, uses inexpensive raw materials, and is suitable for large-scale industrial production.

[0034] The third technical solution of the present invention provides an application of the above-mentioned O2-type lithium-rich manganese-based cathode material in the preparation of lithium-ion battery electrodes or lithium-ion batteries.

[0035] The fourth technical solution of the present invention provides a positive electrode sheet, wherein the active component of the positive electrode sheet includes the above-mentioned O2-type lithium-rich manganese-based positive electrode material.

[0036] Fifth technical solution of the present invention: A lithium-ion battery is provided, wherein the positive electrode of the lithium-ion battery is the aforementioned positive electrode sheet.

[0037] Furthermore, the lithium-ion battery also includes a negative electrode and an electrolyte.

[0038] Optionally, the negative electrode material used in the negative electrode sheet is carbon material or metallic lithium.

[0039] Optionally, the electrolyte includes a lithium salt and a solvent.

[0040] Preferably, the lithium salt includes at least one of lithium hexafluorophosphate, lithium perchlorate, and lithium trifluoromethanesulfonate.

[0041] Preferably, the solvent includes at least one selected from propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and fluoroethylene carbonate.

[0042] The present invention discloses the following technical effects: The O2-type lithium-rich manganese-based cathode material provided by this invention is prepared by ion exchange of a P2-type sodium-lithium-nickel-manganese base oxide with a specific Ni / Mn stoichiometric ratio and a lithium salt. 3+ The Jahn-Teller effect causes lattice distortion, which enhances the strength of the Ni-O bond. The O2 phase lattice structure inhibits the migration of transition metal atoms during cycling and prevents oxygen loss during cycling, greatly alleviating voltage decay. The material has an average voltage decay of 0.64 mV / cycle in the first 100 cycles at 80 mAh / g, and the capacity retention rate can reach 94% after 100 cycles.

[0043] The preparation method of this invention is simple and suitable for large-scale industrial production. Through co-precipitation and ion exchange treatments, a pillar effect is achieved for Ni to enter the lithium layer, generating quasi-three-dimensional lithium-ion diffusion channels and increasing the interlayer spacing. This improves the lithium-ion diffusion coefficient and enhances the rate performance of the material, which still maintains a high specific capacity of 180 mAh / g at 0.5C. Attached Figure Description

[0044] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 The images show the XRD patterns of the materials obtained in Examples 1-3 and Comparative Examples 1-2.

[0045] Figure 2The image shows the SEM image of the material prepared in Example 1.

[0046] Figure 3 The image shows a STEM image of the material prepared in Example 1.

[0047] Figure 4 XPS image of the material prepared in Example 1.

[0048] Figure 5 The first-week charge-discharge curves of the batteries formed from the materials prepared in Examples 1-3 and Comparative Examples 1-2 are shown.

[0049] Figure 6 The first 50 charge-discharge curves of the battery formed from the material prepared in Example 1.

[0050] Figure 7 Rate cycling curves of batteries formed from the materials prepared in Example 1 and Comparative Example 1.

[0051] Figure 8 Charge-discharge cycle curves of the batteries formed by the materials prepared in Example 1 and Comparative Example 1. Detailed Implementation

[0052] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0053] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0054] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0055] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be readily apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0056] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0057] Unless otherwise specified, all raw materials and reagents involved in the specific embodiments of this invention are commercially available products.

[0058] Unless otherwise specified, room temperature and normal temperature in the specific embodiments of this invention refer to 20-30℃.

[0059] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0060] In some specific embodiments, the present invention provides an O2-type lithium-rich manganese-based cathode material with the chemical formula Li. x [Li y Mn z Ni u Co v O2, of which 0.6 <x≤0.9,0.1≤y≤0.3,0.6≤z≤0.7,0.15≤u≤0.25,0≤v≤0.13。

[0061] In some preferred solutions, 0.65≤x≤0.8, 0.1≤y≤0.2, and 0.6≤z≤0.7.

[0062] For example, x can be 0.6, 0.65, 0.7, 0.85, 0.9 or any two of the above values; y can be 0.1, 0.15, 0.2, 0.25, 0.3 or any two of the above values; and z can be 0.6, 0.63, 0.67, 0.7 or any two of the above values.

[0063] This O2-type lithium-rich manganese-based cathode material is an O2-type metastable layered transition metal oxide with an O2 structure, belonging to the R3̅m space group or the C2 / m space group, or a combination of both. Oxygen atoms are arranged in a cubic close-packed (ABAC) configuration, and lithium ions occupy octahedral sites (O sites). The characteristic of this O2-type layered oxide is the alternating arrangement of transition metal layers (TMO2) and lithium ion layers, with lithium layers located between the transition metal layers, providing channels for lithium ion insertion / extraction.

[0064] This O2-type lithium-rich manganese-based cathode material has a layered crystal structure with a thickness of 2–10 μm and a width of 2–15 μm. Thickness refers to the dimension of the material in the direction perpendicular to the layered plane, which can be measured by means of scanning electron microscopy (SEM) or transmission electron microscopy (TEM); width refers to the lateral dimension of the material in the direction of the layered plane, which can be characterized by microscopic techniques such as SEM or TEM.

[0065] Ni of the O2-type lithium-rich manganese-based cathode material 3+ Chemical states can be characterized using techniques such as X-ray absorption near-edge structure (XANES) or X-ray photoelectron spectroscopy (XPS).

[0066] This invention adjusts the stoichiometric ratio between Ni and Mn to induce the appearance of Ni in the original state of the material. 3+ The Jahn-Teller effect causes it to migrate to the lithium layer as a pillar atom, creating a quasi-three-dimensional lithium diffusion channel to promote lithium-ion diffusion. The O2 phase inhibits the migration of transition metal atoms and the loss of lattice oxygen during subsequent cycling, slows down particle cracking, and improves cycling performance.

[0067] In addition, in some specific embodiments, the present invention provides a method for preparing the above-mentioned O2-type lithium-rich manganese-based cathode material, the steps of which include: S1, according to the chemical formula Li x [Li y Mn z Ni u Co v O2 is used to prepare raw materials, of which 0.6 <x≤0.9,0.1≤y≤0.3,0.6≤z≤0.7,0.15≤u≤0.25,0≤v≤0.13。

[0068] S2. Prepare nickel, manganese, cobalt, and aluminum sources with a molar concentration of 1-2 mol·L⁻¹. -1 A solution of mixed salts of transition metals; The nickel source is at least one of nickel sulfate, acetate, and nitrate; The manganese source is at least one of manganese sulfate, acetate and nitrate; The cobalt source is at least one of cobalt sulfate, acetate, and nitrate; The aluminum source is at least one of aluminum sulfate, acetate and nitrate.

[0069] S3. Under an inert atmosphere, prepare a solution of a mixed transition metal salt and a pH adjusting solution (ammonia solution and / or ammonium bicarbonate solution, with a molar concentration of 1-2 mol·L⁻¹). -1 ) and complexing agent solutions (citric acid solution and / or ethylene glycol solution, molar concentration of 0.1-1 mol·L⁻¹)-1 Simultaneously, add the solution to the reaction vessel, adjust the pH of the mixed solution to 8-10 using a pH adjuster, and under stirring conditions, add the precipitant solution (sodium carbonate solution and / or sodium hydroxide solution, molar concentration of 1.5-2.5 mol·L⁻¹) to the reaction vessel by titration. -1 Continue stirring to allow the reaction to proceed. The stirring speed is 500-1500 rpm, the temperature is 40-85℃, and the time is 6-12 h. Then, after aging, centrifugation, and drying, the transition metal salt precursor is obtained. The molar ratio of metal salt to complexing agent in the transition metal mixed salt solution is 5-10; the molar ratio of metal salt to precipitant in the transition metal mixed salt solution is 1:(1~1.3). When adding the transition metal mixed salt solution to the reactor, the feed flow rate is 2~4 L·h. -1 The feed flow rate of the complexing agent solution is 0.5~2 L·h. -1 The feed flow rate of the pH adjuster solution is 1~4 L·h. -1 The feed flow rate of the precipitant solution is 0.02~0.05 L·h. -1 .

[0070] S4. The transition metal salt precursor is mixed with the lithium source and sodium source, ground, and then heated to 400-500℃ at a heating rate of 3-6℃ / min in air atmosphere, held for 4-6h, and then heated to 800-900℃ at a heating rate of 3-8℃ / min, held for 15-20h, and then cooled to obtain sodium layered oxide.

[0071] Among them, the lithium source and sodium source are in accordance with the chemical formula Li x [Li y Mn z Ni u Co v Prepare O2 according to the stoichiometric ratio shown, or prepare it in excess of 1-10% according to the stoichiometric ratio shown; the sodium source includes at least one of sodium carbonate, sodium acetate, sodium fluoride, sodium nitrate and sodium hydroxide; the lithium source includes at least one of lithium carbonate, lithium hydroxide and lithium oxalate; the grinding method includes ball milling, using equipment such as a planetary ball mill for ball milling, and the ball milling conditions include: a rotation speed of 150-500 rpm and a time of 2-6 h.

[0072] S5, sodium layered oxide and 5-10 times the molar amount of lithium source are subjected to ion exchange reaction at 250-400℃ for 3-10h. After the reaction is completed, the material is washed, filtered and dried to obtain the O2-type lithium-rich manganese-based cathode material. The lithium source includes at least one of lithium chloride, lithium hydroxide, lithium carbonate, lithium acetate, lithium oxalate, lithium nitrate, lithium oxide, and lithium peroxide.

[0073] In the above preparation method, lithium ions are formed by high-temperature ionization of the lithium source through ion exchange, which replaces the sodium ions of the sodium-lithium-nickel-manganese-based precursor to obtain the O2-type metastable phase lithium-rich manganese-based cathode material.

[0074] In the above preparation method, the stoichiometric ratio between transition metals is adjusted by regulating the mass ratio of transition metal salts, thereby causing the original material to exhibit Ni. 3+ The Jahn-Teller effect causes it to migrate into the lithium layer as a pillar atom.

[0075] This invention synthesizes a P2-type sodium layered oxide and then undergoes ion exchange with an excess lithium salt to obtain an O2-type metastable lithium-rich manganese-based layered transition metal oxide material. By adjusting the Ni / Mn stoichiometric ratio, the irreversible migration of transition metal atoms during cycling is suppressed, reducing lattice oxygen loss during cycling. This improves the cycle performance of lithium-ion batteries made from this material. The presence of Ni... 3+ This improves the cycle performance of lithium-ion batteries made from the material. Specifically, this application mainly designs an O2-type lithium-rich manganese-based cathode material with a specific stoichiometric ratio, which, based on charge conservation, incorporates Ni... 3+ The Jahn-Teller effect induces lattice distortion, causing the NiO6 octahedrons to deform and migrate to the lithium layer, forming a pillar effect. This creates quasi-three-dimensional lithium-ion diffusion channels, promoting lithium-ion diffusion. Simultaneously, the distortion shortens the distance between Ni and O atoms, increasing the strength of the Ni-O bond and effectively reducing lattice oxygen loss during cycling. It also stabilizes the valence state of transition metal atoms surrounding oxygen atoms, suppressing voltage decay during cycling and increasing cycling stability.

[0076] Example 1 O2-type lithium-rich manganese-based cathode material, the original material chemical state is Ni. 2+ / Ni 3+ and Mn 4+ The chemical formula is Li 0.69 [Li 0.12 Ni 0.22 Mn 0.66 O2, the preparation steps include: S1. Weigh out nickel sulfate and manganese sulfate according to the molar ratio Ni:Mn = 0.25:0.75, and dissolve the above raw materials in deionized water to prepare a total nickel-manganese molar concentration of 1.5 mol·L⁻¹. -1 A solution of mixed transition metal salts.

[0077] Deionized water was used to prepare an ammonia molar concentration of 1.5 mol·L⁻¹. -1 Ammonia solution (pH adjuster solution).

[0078] Prepare a solution with a citric acid molar concentration of 0.5 mol·L⁻¹. -1 Citric acid solution (complexing agent solution).

[0079] Prepare sodium carbonate with a molar concentration of 2 mol·L⁻¹ -1 Sodium carbonate solution (precipitant solution).

[0080] S2. Transfer the transition metal mixed salt solution to a reaction vessel. Under a nitrogen atmosphere, add ammonia solution and citric acid solution to the reaction vessel. Adjust the pH of the mixed solution to 7.5 using ammonia solution. The molar ratio of metal salt to complexing agent (citric acid) in the transition metal mixed salt solution is 5. Under a stirring speed of 1000 rpm, slowly add sodium carbonate solution to the reaction vessel by titration, controlling the molar ratio of metal salt to sodium carbonate to be 1:1.3. React for 12 hours under a stirring speed of 1000 rpm and a temperature of 65℃. After the reaction, age the sample, centrifuge, and vacuum dry to obtain the transition metal carbonate precursor.

[0081] S3. The transition metal carbonate precursor is uniformly mixed with sodium source (sodium carbonate) and lithium source (lithium carbonate) according to the molar ratio designed by the chemical formula, and ball-milled for 3 hours at a speed of 400 rpm to obtain the mixture.

[0082] The mixture was placed in a tube furnace and heated to 500°C at a heating rate of 5°C / min in air atmosphere and held at that temperature for 5 hours. Then, it was heated to 900°C at a heating rate of 5°C / min and held at that temperature for 16 hours. Finally, it was allowed to cool naturally to room temperature to obtain sodium layered oxide.

[0083] S4. Sodium layered oxide and 8 times the molar amount of lithium salt were ion exchanged at 320°C for 5 hours. The lithium salt composition was lithium chloride and lithium nitrate in a mass ratio of 7:3. The product was washed, filtered and dried to obtain the O2-type lithium-rich manganese-based cathode material, which was denoted as Sample 1.

[0084] Example 2 Compared to Example 1, the original material's chemical state was Ni. 2+ / Ni 3+ Co 3+ and Mn 4+ The chemical formula is Li 0.69 [Li 0.12 Ni 0.14 Co 0.14 Mn 0.48 According to the designed chemical formula, cobalt sulfate was added during the preparation of the transition metal mixed salt solution with the total concentration remaining unchanged. The resulting O2-type lithium-rich manganese-based cathode material was designated as sample 2.

[0085] Example 3 Compared to Example 1, the chemical formula Li was designed 0.72 [Li 0.12 Ni 0.176 Mn 0.704 O2, the original material's chemical state is Ni 2 + / Ni 3+ and Mn 4+ According to the designed chemical formula, in step S1, nickel sulfate and manganese sulfate are weighed in a molar ratio of Ni:Mn = 0.2:0.8, and the above raw materials are dissolved in deionized water to prepare a solution with a total nickel-manganese concentration of 1 mol·L⁻¹. -1 The amount of sodium carbonate solution in step S2 was adjusted accordingly, and the resulting O2-type lithium-rich manganese-based cathode material was denoted as sample 3.

[0086] Comparative Example 1 Lithium-rich manganese-based cathode material, the original material chemical state is Ni 2+ and Mn 4+ The chemical formula is Li 0.69 [Li 0.12 Ni 0.145 Mn 0.725 O2, the preparation steps include: S1. Weigh out nickel sulfate and manganese sulfate according to the molar ratio Ni:Mn = 0.166:0.833, and dissolve the above raw materials in deionized water to prepare a total nickel-manganese molar concentration of 1 mol·L⁻¹. -1 A solution of mixed transition metal salts.

[0087] Deionized water was used to prepare an ammonia molar concentration of 1.5 mol·L⁻¹. -1 Ammonia solution (pH adjuster solution).

[0088] Prepare a solution with a citric acid molar concentration of 0.5 mol·L⁻¹. -1 Citric acid solution (complexing agent solution).

[0089] Prepare sodium carbonate with a molar concentration of 2 mol·L⁻¹ -1 Sodium carbonate solution (precipitant solution).

[0090] S2. Transfer the transition metal mixed salt solution to a reaction vessel. Under a nitrogen atmosphere, add ammonia solution and citric acid solution to the reaction vessel. Adjust the pH of the mixed solution to 7.5 using ammonia solution. The molar ratio of metal salt to complexing agent (citric acid) in the transition metal mixed salt solution is 5. Under a stirring speed of 1000 rpm, slowly add sodium carbonate solution to the reaction vessel by titration, controlling the molar ratio of metal salt to sodium carbonate to be 1:1.3. React for 12 hours under a stirring speed of 1000 rpm and a temperature of 65℃. After the reaction, age the sample, centrifuge, and vacuum dry to obtain the transition metal carbonate precursor.

[0091] S3. The transition metal carbonate precursor is uniformly mixed with sodium and lithium sources according to the molar ratio designed by the chemical formula, and ball-milled at 400 rpm for 3 hours to obtain the mixture.

[0092] The mixture was placed in a tube furnace and heated to 500°C at a heating rate of 5°C / min in air atmosphere and held at that temperature for 5 hours. Then, it was heated to 900°C at a heating rate of 5°C / min and held at that temperature for 16 hours. Finally, it was allowed to cool naturally to room temperature to obtain sodium layered oxide.

[0093] S4. Sodium layered oxide and 8 times the molar amount of lithium salt were ion exchanged at 320°C for 5 hours. The lithium salt composition was lithium chloride and lithium nitrate in a mass ratio of 7:3. The product was washed, filtered and dried to obtain the lithium-rich manganese-based cathode material, which was designated as control sample 1.

[0094] Comparative Example 2 The lithium-ion battery O3-type lithium-rich manganese-based cathode material is designed with the chemical formula Li. 1.2 Ni 0.2 Mn 0.6 O2, the preparation steps include: S1. Weigh out nickel sulfate and manganese sulfate according to the molar ratio Ni:Mn = 0.25:0.75, and dissolve the above raw materials in deionized water to prepare a total nickel-manganese molar concentration of 1 mol·L⁻¹. -1 A solution of mixed transition metal salts.

[0095] Deionized water was used to prepare an ammonia molar concentration of 1.5 mol·L⁻¹. -1 Ammonia solution (pH adjuster solution).

[0096] Prepare a solution with a citric acid molar concentration of 0.5 mol·L⁻¹. -1 Citric acid solution (complexing agent solution).

[0097] Prepare sodium carbonate with a molar concentration of 2 mol·L⁻¹ -1 Sodium carbonate solution (precipitant solution).

[0098] S2. Transfer the transition metal mixed salt solution to a reaction vessel. Under a nitrogen atmosphere, add ammonia solution and citric acid solution to the reaction vessel. Use ammonia solution to adjust the pH of the mixed solution to 8. The molar ratio of metal salt to complexing agent (citric acid) in the transition metal mixed salt solution is 5. Under the condition of stirring speed of 1000 rpm, slowly add sodium carbonate solution to the reaction vessel by titration, controlling the molar ratio of metal salt to sodium carbonate to be 1:1.3. React for 12 h under the conditions of stirring speed of 1000 rpm and temperature of 65℃. After the reaction is completed, the sample is aged, centrifuged and vacuum dried to obtain the transition metal carbonate precursor.

[0099] S3. The transition metal carbonate precursor is uniformly mixed with sodium source (sodium carbonate) and lithium source (lithium carbonate) according to the molar ratio designed by the chemical formula, and ball-milled for 3 hours at a speed of 400 rpm to obtain the mixture.

[0100] The mixture was placed in a tube furnace and heated to 500°C at a heating rate of 5°C / min under air atmosphere and held at that temperature for 5 hours. Then, it was heated to 900°C at a heating rate of 5°C / min and held at that temperature for 12 hours. Finally, it was allowed to cool naturally to room temperature to obtain O3-type lithium-rich manganese-based cathode material, which was designated as control sample 2.

[0101] Test case The stoichiometric ratios of the samples in the above embodiments and comparative examples are shown in Table 1 below.

[0102] Table 1 Material characterization: X-ray diffraction (XRD) analysis was performed on the materials obtained in the examples and comparative examples, such as... Figure 1 As shown.

[0103] Figure 1 The figures show the XRD patterns of the materials obtained in Examples 1-3 and Comparative Examples 1-2. As can be seen from the figures, Sample 1 is an O2 structure material with space group R3̅m and C2 / m. Analysis revealed that Sample 1 is Li. 0.69 [Li 0.12 Ni 0.22 Mn 0.66 Sample 2 is a material with an O2 structure, space group R3̅m and C2 / m. Analysis revealed that sample 2 is Li. 0.69 [Li 0.12 Ni 0.14 Co 0.14 Mn 0.48 Sample 3 is a material with an O2 structure, space group R3̅m and C2 / m. Analysis revealed that sample 3 is Li. 0.72 [Li0.12 Ni 0.176 Mn 0.704 O2; Comparative sample 1 is Li 0.69 [Li 0.12 Ni 0.145 Mn 0.725 O2; Comparative sample 2 is Li 1.2 Ni 0.2 Mn 0.6 O2. Except for the material in Comparative Example 2, which exhibits an O3 phase structure, all other samples exhibit an O2 phase structure.

[0104] Figure 2 The image shows a SEM image of the material prepared in Example 1. As can be seen from the image, Sample 1 of Example 1 has a secondary particle morphology with a particle size of approximately 10 μm.

[0105] Figure 3 The image shows a STEM image of the material prepared in Example 1. As can be seen from the image, the bulk phase of sample 1 is an O2 phase structure, with some Ni atoms migrating to the lithium layer.

[0106] Figure 4 The image shows the XPS plot of the material prepared in Example 1. As can be seen from the plot, Ni in Sample 1 exists in both +2 and +3 valence states, with roughly equal amounts.

[0107] Performance characterization: Preparation of the positive electrode sheet: The materials prepared in the examples and comparative examples, conductive carbon black (Super P), and binder polyvinylidene fluoride (PVDF) were weighed in a mass ratio of 8:1:1. Based on a 3% volume fraction of PVDF (NMP solution), the mixture was uniformly dispersed in N-methylpyrrolidone (NMP) solvent to obtain a mixed slurry. The mixed slurry was uniformly coated to a thickness of 200µm on the positive current collector coated with carbon aluminum foil. After vacuum drying overnight, it was cut into circular positive electrode sheets with a diameter of 12mm.

[0108] Assembly of lithium-ion batteries: The CR2032 button cell is assembled using the above-mentioned positive electrode as the positive electrode, the negative electrode as a metallic lithium sheet, and the electrolyte as 1 mol / L LiPF6 (in EC:DEC=1:1, 5% FEC, Vol%). It is then assembled with other necessary battery components (separator and casing, etc.) in a glove box filled with high-purity argon gas to form a button cell.

[0109] The assembled lithium-ion batteries were subjected to performance testing within a voltage window of 2.0–4.8V. Specifically, charge-discharge performance testing was conducted in a battery testing system, including: the first charge-discharge test and a 100-cycle test. The test temperature was 20°C, the rate was 0.2C, and 1C = 250 mA·g. -1The voltage window is 2.0~4.8V. The test results are shown in Table 2.

[0110] Table 2 Figure 5 The first-cycle charge-discharge curves of the batteries formed from the materials prepared in Examples 1-3 and Comparative Examples 1-2 are shown. Figure 5 As can be seen from the data in Table 2, the initial charge capacity of the battery prepared in Example 1 is 233 mAh·g. -1 The initial discharge capacity is 230 mAh·g -1 The battery exhibits an oxygen oxidation plateau at 4.5V and excellent coulombic efficiency (99%). However, the coulombic efficiencies of Examples 2-3 and Comparative Example 1 are relatively low. The initial charge capacity of the fabricated battery is 254-264 mAh·g. -1 The initial discharge capacity is 218~246 mAh·g -1 All samples exhibited a clear oxygen plateau around 4.5V, indicating the activation of the Li2MnO3 phase. Comparative Example 2 is a common O3-type lithium-rich manganese-based cathode material, which shows higher charge-discharge capacity than other samples, but its coulombic efficiency (90%) is relatively low.

[0111] Figure 6 The figure shows the charge-discharge curves of the battery formed by the material prepared in Example 1 for the first 50 cycles. As can be seen from the figure, at a rate of 0.2C (1C = 250 mAh / g), the average voltage decay per cycle is 0.64 mV. This indicates that the material effectively prevents oxygen loss and suppresses voltage decay during cycling.

[0112] Figure 7 Rate cycling curves of batteries formed from the materials prepared in Example 1 and Comparative Example 1 are shown in the figures. As can be seen from the figures, the cycle capacity of Example 1 is significantly better than that of Comparative Example 1 as the rate of increase gradually increases. Combined with... Figure 4 It can be shown that the unique Ni in Example 1 3+ This induces Ni atoms to enter the lithium layer. This not only increases the interlayer spacing of lithium atoms but also creates three-dimensional lithium-ion diffusion channels, thereby improving the lithium-ion diffusion coefficient.

[0113] Figure 8 The charge-discharge cycle curves of the batteries formed from the materials prepared in Example 1 and Comparative Example 1 are shown in the figure. As can be seen from the figure, after 100 cycles at a rate of 0.2C (1C = 250 mAh / g), the capacity retention rates of Example 1 and Comparative Example 1 are 94% and 74%, respectively, indicating that Ni… 3+ The Jahn-Teller effect enhances the Ni-O bond, making it less prone to oxygen atom loss and stabilizing oxygen activity. Simultaneously, the pillar effect of Ni atoms in the lithium layer prevents the material from collapsing during cycling. Compared to Comparative Example 1, it maintains a higher capacity retention rate.

[0114] In summary, the lithium-ion battery assembled using lithium-rich manganese-based cathode materials with specific elemental ratios in this invention exhibits a high specific capacity (247 mAh / g at a 0.05C rate and a high cutoff voltage of 4.8V). -1 The above-mentioned reversible specific capacity, excellent cycle performance (voltage decay of only 0.64mV / cycle in the first 50 cycles, and capacity retention of 94% after 100 cycles), and high rate stability indicate that the oxygen activity remains stable and the lithium-ion diffusion coefficient is high during the material's operation. This is because the lithium-rich manganese-based cathode material used in this application embodiment contains Ni. 3+ The Jahn-Teller effect allows Ni atoms to migrate into the lithium layer as pillar atoms. This strengthens the Ni-O bond, expands the lithium-ion inlet and outlet channels, and stabilizes oxygen activity.

[0115] It is evident that the lithium-rich manganese-based material provided by this invention can effectively improve rate performance while suppressing voltage decay and oxygen loss during cycling, thereby enhancing cycle stability.

[0116] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0117] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An O2-type lithium-rich manganese-based cathode material, characterized in that, The chemical formula of the O2-type lithium-rich manganese-based cathode material is Li. x [Li y Mn z Ni u Co v O2, of which 0.6 <x≤0.9,0.1≤y≤0.3,0.6≤z≤0.7,0.15≤u≤0.25,0≤v≤0.13。 2. The O2-type lithium-rich manganese-based cathode material as described in claim 1, characterized in that, The O2-type lithium-rich manganese-based cathode material has an O2-type layered structure with local oxygen atom stacking in an ABAC pattern. Li layers and transition metal layers are arranged alternately, and the layers are connected by oxygen atoms. And / or, the thickness of the O2-type lithium-rich manganese-based cathode material is 2-10 μm and the width is 2-15 μm.

3. A method for preparing the O2-type lithium-rich manganese-based cathode material according to claim 1 or 2, characterized in that the step... include: Transition metal salt precursors were prepared by co-precipitation treatment using nickel, manganese, cobalt and aluminum sources as reactants. The transition metal salt precursor was mixed evenly with a sodium source and a first lithium source, and then ground and calcined to obtain a layered sodium oxide material. The layered sodium oxide is subjected to ion exchange treatment with a second lithium source to obtain the lithium-rich manganese-based cathode material.

4. The preparation method according to claim 3, characterized in that, The coprecipitation treatment steps include: preparing a transition metal mixed salt solution from the nickel source, manganese source, cobalt source and aluminum source; mixing it evenly with a complexing agent under an inert atmosphere; adjusting the pH of the system to 8-10; adding a precipitant under stirring conditions to carry out a coprecipitation reaction; and after the reaction is completed, aging, centrifuging and drying are performed to obtain the transition metal salt precursor. And / or, the preparation steps of the layered sodium oxide material include: mixing the transition metal salt precursor with the first lithium source and sodium source, grinding, heating to 400-500℃ at a heating rate of 3-6℃ / min in air atmosphere, holding at that temperature for 4-6h, then heating to 800-900℃ at a heating rate of 3-8℃ / min, holding at that temperature for 15-20h, and cooling to obtain the layered sodium oxide.

5. The preparation method according to claim 4, characterized in that, The nickel source is at least one of nickel sulfate, acetate and nitrate; And / or, the manganese source is at least one of manganese sulfate, acetate and nitrate; And / or, the cobalt source is at least one of cobalt sulfate, acetate and nitrate; And / or, the aluminum source is at least one of aluminum sulfate, acetate and nitrate; And / or, the complexing agent is added in solution form, comprising a citric acid solution and / or an ethylene glycol solution, with a molar concentration of 0.1-1 mol·L⁻¹. -1 ; And / or, the pH value of the adjustment system is 8-10, which is the pH value adjusted by a pH adjusting agent solution; the pH adjusting agent solution includes an aqueous ammonia solution and / or an ammonium bicarbonate solution, with a molar concentration of 1-2 mol·L⁻¹. -1 ; And / or, the precipitant is added in solution form, comprising sodium carbonate solution and / or sodium hydroxide solution, with a molar concentration of 1.5-2.5 mol·L⁻¹. -1 ; And / or, the molar ratio of the metal salt to the complexing agent in the transition metal mixed salt solution is 5-10; And / or, the molar ratio of metal salt to precipitant in the transition metal mixed salt solution is 1:(1~1.3). And / or, the stirring speed of the coprecipitation reaction is 500-1500 rpm, the temperature is 40-85℃, and the time is 6-12 h; And / or, the first lithium source and sodium source are in accordance with the chemical formula Li x [Li y Mn z Ni u Co v Prepare O2 according to the stoichiometric ratio shown, or prepare it in excess of 1-10% according to the stoichiometric ratio shown. And / or, the sodium source includes at least one of sodium carbonate, sodium acetate, sodium fluoride, sodium nitrate, and sodium hydroxide; And / or, the first lithium source includes at least one of lithium carbonate, lithium hydroxide, and lithium oxalate.

6. The preparation method according to claim 3, characterized in that, The steps of the ion exchange treatment include: Sodium layered oxide and a second lithium source undergo an ion exchange reaction at 250-400℃ for 3-10 hours. After the reaction is completed, the material is washed, filtered, and dried to obtain the O2-type lithium-rich manganese-based cathode material.

7. The preparation method according to claim 6, characterized in that, The second lithium source includes at least one of lithium chloride, lithium hydroxide, lithium carbonate, lithium acetate, lithium oxalate, lithium nitrate, lithium oxide, and lithium peroxide; And / or, the molar ratio of the second lithium source to the sodium layered oxide is 5-10:

1.

8. The application of the O2-type lithium-rich manganese-based cathode material according to claim 1 or 2 in the preparation of lithium-ion battery electrodes or lithium-ion batteries.

9. A positive electrode sheet, characterized in that, The active component of the positive electrode sheet includes the O2-type lithium-rich manganese-based positive electrode material as described in claim 1 or 2.

10. A lithium-ion battery, characterized in that, The positive electrode of the lithium-ion battery is the positive electrode sheet as described in claim 9.

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