Lithium-rich manganese-based oxides, methods of preparation, cathode materials, and batteries

Abstract

This disclosure provides a lithium-rich manganese-based oxide, its preparation method, a cathode material, and a battery. The lithium-rich manganese-based oxide exhibits an O2 phase crystal structure, and its chemical formula is Li. m [Li 0.2‑x T x Mn 0.8 O2, wherein 0.6≤m≤0.8, 0<x<0.2, and T is selected from a combination of doped metal elements and vacancies or from one or more doped metal elements selected from Al, Ge, Mg, Ti, Zr, and Nb. This lithium-rich manganese-based oxide exhibits significantly higher initial discharge specific capacity and significantly lower voltage decay.

Description

Technical Field

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

[0002] Lithium-ion batteries are a clean and efficient energy storage technology, playing an increasingly important role in the development of the energy sector. They have become a common power source for portable electronic devices and electric vehicles, playing a crucial role in these applications. Key performance indicators of lithium-ion batteries, such as energy density, cycle life, power density, and safety, are closely related to the electrode materials used. Therefore, developing novel electrode materials with high energy density, high power density, long lifespan, and high energy efficiency has become an urgent need.

[0003] Traditional O3-type electrode materials, such as lithium cobalt oxide (LiCoO2) and ternary nickel cobalt manganese oxide (NCM), offer high energy densities but face challenges including high cost, resource scarcity, and environmental pollution. While materials like lithium iron phosphate (LiFePO4) and spinel manganese oxide (LiMn2O4) are lower in cost, their energy densities are also lower, making them unsuitable for growing demand. Compared to traditional cathode materials, lithium-rich manganese-based oxides possess higher theoretical specific capacity and are a promising new type of cathode material. However, lithium-rich manganese-based oxides are constrained by severe transition metal dissolution and irreversible phase transitions from layered to spinel phases, resulting in significantly lower discharge specific capacity and voltage degradation during cycling, posing substantial challenges to their further commercial application. Summary of the Invention

[0004] Therefore, it is necessary to provide a lithium-rich manganese-based oxide electrode material that improves discharge specific capacity and reduces voltage decay during cycling, in order to address the problems mentioned in the background art.

[0005] In a first aspect, this disclosure provides a lithium-rich manganese-based oxide, which has an O2 phase crystal structure and the chemical formula of the lithium-rich manganese-based oxide is Li. m [Li 0.2-x T x Mn 0.8 O2, wherein 0.6≤m≤0.8, 0<x<0.2, and T is selected from a combination of doped metal elements and vacancies or from doped metal elements, wherein the doped metal elements are selected from one or more of Al, Ge, Mg, Ti, Zr and Nb.

[0006] According to some embodiments of this disclosure, in the lithium-rich manganese-based oxide, 0 < x ≤ 0.1.

[0007] According to some embodiments of this disclosure, the doped metal element in the lithium-rich manganese-based oxide includes Mg.

[0008] According to some embodiments of this disclosure, the chemical formula of the lithium-rich manganese-based oxide is Li. m [Li 0.2-x Mg x Mn 0.8 O2.

[0009] According to some embodiments of this disclosure, the lithium-rich manganese-based oxide is in the form of primary particles, and the particle size of the lithium-rich manganese-based oxide is ≤2μm.

[0010] According to some embodiments of this disclosure, the lithium-rich manganese-based oxide has a superlattice structure, and in the X-ray diffraction characterization results of the lithium-rich manganese-based oxide, there are diffraction peaks corresponding to the superlattice structure between 21° and 25°.

[0011] Secondly, this disclosure also provides a method for preparing lithium-rich manganese-based oxides as described in any of the above embodiments, comprising the following steps:

[0012] Sodium source, first lithium source, doped metal source and manganese source are mixed in a ratio of m:(0.2-x):x:0.8 and then calcined to form a precursor material, wherein the doped metal source contains the doped metal element;

[0013] The precursor material is mixed with an excess of a second lithium source and then subjected to ion exchange treatment, so that the sodium element in the precursor material is replaced with lithium element.

[0014] According to some embodiments of this disclosure, the sodium source, the first lithium source, the doped metal source, and the manganese source satisfy at least one of the following features (1) to (4):

[0015] (1) The sodium source is selected from one or more of sodium hydroxide, sodium carbonate, and sodium oxide;

[0016] (2) The first lithium source is selected from one or more of lithium hydroxide, lithium carbonate, and lithium oxide;

[0017] (3) The doped metal source is selected from the oxide of the doped metal element;

[0018] (4) The manganese source is selected from one or more of manganese carbonate, manganese dioxide, basic manganese oxide, manganese monoxide and manganese tetroxide.

[0019] According to some embodiments of this disclosure, during the calcination process, the calcination temperature is controlled at 700℃~900℃ and the calcination time is controlled at 10h~15h.

[0020] According to some embodiments of this disclosure, the second lithium source is selected from one or more of lithium nitrate and lithium chloride, and the step of performing ion exchange treatment includes: mixing the precursor material with the second lithium source and heating it to 280°C~360°C, and maintaining it for 3h~6h.

[0021] According to some embodiments of this disclosure, the molar ratio of sodium in the precursor material to lithium in the second lithium source is 1:(5~15).

[0022] Thirdly, this disclosure also provides a cathode material comprising lithium-rich manganese-based oxide as described in any of the above embodiments.

[0023] Fourthly, this disclosure also provides a battery, characterized in that it includes a positive electrode, a negative electrode and an electrolyte, wherein the positive electrode and the negative electrode are disposed opposite to and spaced apart, the electrolyte is disposed between the positive electrode and the negative electrode, and the positive electrode includes a lithium-rich manganese-based oxide as described in any of the above embodiments.

[0024] The lithium-rich manganese-based oxide disclosed herein is an O2-phase lithium-rich manganese-based oxide. Furthermore, by introducing a small amount of doped metal elements to modulate the superlattice structure within its transition metal layer, this disclosure enhances the activity and reversibility of anionic redox reactions, effectively reduces transition metal dissolution, suppresses the irreversible phase transition from layered to spinel phase, and significantly improves the stability of its crystal structure. Experimental verification shows that, compared to other conventional lithium-rich manganese-based oxides, this lithium-rich manganese-based oxide exhibits significantly higher initial discharge specific capacity and significantly lower voltage decay.

[0025] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0026] Figure 1 A schematic diagram showing the morphology of the lithium-rich manganese-based oxide of Example 1 as observed using a scanning electron microscope;

[0027] Figure 2 The X-ray diffraction pattern of the lithium-rich manganese-based oxide in Example 1 is shown.

[0028] Figure 3 The rate performance test results of the battery prepared by lithium-rich manganese-based oxide in Example 1;

[0029] Figure 4 The first charge-discharge curves and the second charge-discharge curves of the battery prepared by the lithium-rich manganese-based oxide of Example 1 at a current density of 0.1C. Detailed Implementation

[0030] To facilitate understanding of this document, a more comprehensive description will be provided below. Preferred embodiments are given herein. However, this document can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to make the content of this document more thorough and comprehensive.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this applies. The terminology used herein in the specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the document.

[0032] It should be understood that when an element or layer is referred to as "on," "adjacent to," "connected to," or "coupled to" other elements or layers, it may be directly on, adjacent to, connected to, or coupled to other elements or layers, or there may be intervening elements or layers. Conversely, when an element is referred to as "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" other elements or layers, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc., may be used to describe various elements, components, areas, layers, and / or parts, these elements, components, areas, layers, and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, area, layer, or part from another element, component, area, layer, or part.

[0033] Spatial relation terms such as “below,” “under,” “below,” “below,” “above,” “above,” etc., are used herein for convenience of description to describe the relationship of one element or feature to other elements or features. It should be understood that spatial relation terms are intended to also include different orientations of the device in use and operation. For example, if the device in the figures is flipped, then the element or feature described as “below,” “below,” or “below” other elements or features will be oriented “above” other elements or features. Therefore, the exemplary terms “below” and “under” can include both above and below orientations. Devices may be oriented in other ways (e.g., rotated 90 degrees or other orientations), and the spatial descriptive terms used will be interpreted accordingly.

[0034] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. When used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprise” and / or “comprising,” when used in this specification, identify the presence of features, integers, steps, operations, elements, and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, and / or groups. When used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0035] This disclosure provides a lithium-rich manganese-based oxide, which has an O2 phase crystal structure and the chemical formula of the lithium-rich manganese-based oxide is Li. m [Li 0.2-x T x Mn 0.8 O2, where 0.6≤m≤0.8, 0<x<0.2, and T is selected from a combination of doped metal elements and vacancies or doped metal elements, wherein the doped metal elements are selected from one or more of Al, Ge, Mg, Ti, Zr and Nb.

[0036] The lithium-rich manganese-based oxide disclosed herein is an O2-phase lithium-rich manganese-based oxide. Furthermore, by introducing a small amount of doped metal elements to modulate the superlattice structure within its transition metal layer, this disclosure enhances the activity and reversibility of anionic redox reactions, effectively reduces transition metal dissolution, suppresses the irreversible phase transition from layered to spinel phase, and significantly improves the stability of its crystal structure. Experimental verification shows that, compared to other conventional lithium-rich manganese-based oxides, this lithium-rich manganese-based oxide exhibits significantly higher initial discharge specific capacity and significantly lower voltage decay.

[0037] In one aspect, an embodiment of this disclosure provides a lithium-rich manganese-based oxide, which has an O2 phase crystal structure and the chemical formula of the lithium-rich manganese-based oxide is Li. m [Li 0.2-x T x Mn 0.8 O2, where 0.6≤m≤0.8, 0<x<0.2, and T is selected from a combination of doped metal elements and vacancies or doped metal elements, wherein the doped metal elements are selected from one or more of Al, Ge, Mg, Ti, Zr and Nb.

[0038] In this embodiment, the lithium-rich manganese-based oxide has a layered structure of the O2 phase. It can be understood that in this layered structure, lithium, doped metal elements or vacancies, and manganese are used to form the transition metal layer, and the doped metal elements or vacancies are used to regulate the superlattice structure within the transition metal layer; their content has a significant impact on the lattice structure and actual performance of the lithium-rich manganese-based oxide.

[0039] It can be understood that the vacancy in this lithium-rich manganese-based oxide refers to a site that should be occupied by a doped metal element but is not. When T is selected from a combination of a doped metal element and a vacancy, the site that could have been occupied by a doped metal element is replaced by the vacancy.

[0040] As some examples of this embodiment, the doping metal element can be selected from one metal element, such as Al, Ge, Mg, Ti, Zr, or Nb. In other examples, the doping metal element can also be a combination of multiple metal elements, such as a combination of Al and Mg, or a combination of Mg and Ti.

[0041] As examples of this embodiment, in lithium-rich manganese-based oxides, 0 < x ≤ 0.1. For example, x can be 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1, or x can be between any two of the above values. When the stoichiometry of the doped metal element is below 0.1, the lattice stability of the lithium-rich manganese-based oxide can be further improved, the initial discharge specific capacity can be increased, and the voltage decay can be reduced.

[0042] As some examples of this embodiment, in lithium-rich manganese-based oxides, m can be 0.6, 0.62, 0.64, 0.66, 0.68, 0.7, 0.72, 0.74, 0.76, 0.78, or 0.8, or m can be between any two of the above values. Optionally, in lithium-rich manganese-based oxides, m can be <0.7. When m is above 0.7, it has a slightly higher initial discharge specific capacity, but it will cause a certain deterioration in both cycle retention and voltage decay.

[0043] As some examples of this embodiment, in lithium-rich manganese-based oxides, the doped metal elements include one or more of Mg, Al, Ti and Ge.

[0044] Among them, the lithium-rich manganese-based oxide with Mg as the dopant element has relatively good charge and discharge performance.

[0045] Furthermore, as some examples of this embodiment, the chemical formula of the lithium-rich manganese-based oxide is Li. m [Li 0.2-xMg x Mn 0.8 O2. For example, the chemical formula of this lithium-rich manganese-based oxide could be Li. m [Li 0.15 Mg 0.05 Mn 0.8 O2, Li m [Li 0.1 Mg 0.1 Mn 0.8 O2, Li m [Li 0.05 Mg 0.15 Mn 0.8 O2, etc.

[0046] As examples of this embodiment, the lithium-rich manganese-based oxide is in the form of primary particles, and the particle size of the lithium-rich manganese-based oxide is ≤2μm. Here, primary particles refer to unaggregated individual crystals, and the particle size of the primary granular lithium-rich manganese-based oxide is relatively small.

[0047] As some examples of this embodiment, the lithium-rich manganese-based oxide has a superlattice structure, and in the X-ray diffraction characterization results of the lithium-rich manganese-based oxide, there are diffraction peaks corresponding to the superlattice structure between 21° and 25°.

[0048] Secondly, this disclosure also provides a method for preparing a lithium-rich manganese-based oxide. The method for preparing the lithium-rich manganese-based oxide includes the following steps S1-S2.

[0049] Step S1: Sodium source, first lithium source, doped metal source and manganese source are mixed in a ratio of m:(0.2-x):x:0.8 and then calcined to form precursor material. The doped metal source contains doped metal elements.

[0050] It is understandable that a sodium source contains sodium, and a sodium source can be a compound containing sodium. A primary lithium source contains lithium, and a primary lithium source can be a compound containing lithium. A doped metal source contains the desired doping metal element, and a doped metal source can be a compound containing a doping metal element. A manganese source contains manganese, and a manganese source can be a compound containing manganese.

[0051] As examples of this embodiment, calcination of the above-mentioned raw materials can form sodium manganese oxide in the P2 phase. The chemical formula of the resulting precursor material is Na. m [Li 0.2-x T x Mn 0.8 O2. It can be understood that the main difference between the precursor material and the desired lithium-rich manganese-based oxide is only the difference between sodium ions and lithium ions. Replacing the sodium ions with lithium ions will form the corresponding lithium-rich manganese-based oxide.

[0052] As examples of this embodiment, the sodium source is selected from one or more of sodium hydroxide, sodium carbonate, and sodium oxide. Using sodium hydroxide, sodium carbonate, and sodium oxide as sodium sources ensures that virtually no impurity elements are introduced during calcination, which is beneficial for the formation of pure-phase sodium manganese oxide.

[0053] As examples of this embodiment, the first lithium source is selected from one or more of lithium hydroxide, lithium carbonate, and lithium oxide. Using lithium hydroxide, lithium carbonate, and lithium oxide as the first lithium source ensures that virtually no impurity elements are introduced during calcination, which is beneficial for the formation of pure-phase sodium manganese oxide.

[0054] As examples of this embodiment, the doping metal source is selected from oxides of doping metal elements. Using oxides as the doping metal source ensures that virtually no impurity elements are introduced during calcination, which is beneficial for forming pure-phase sodium-manganese oxides.

[0055] As examples of this embodiment, the manganese source is selected from one or more of manganese carbonate, manganese dioxide, basic manganese oxide, manganese monoxide, and manganese tetroxide. Using manganese carbonate, manganese dioxide, basic manganese oxide, manganese monoxide, and manganese tetroxide as manganese sources ensures that virtually no impurity elements are introduced during calcination, which is beneficial for forming pure-phase sodium manganese oxide.

[0056] As examples of this embodiment, the sodium source, the first lithium source, the doped metal source, and the manganese source can be mixed by ball milling. Ball milling allows the above-mentioned raw materials to come into full contact and mix evenly, thereby ensuring a more complete reaction between the raw materials in subsequent processes.

[0057] As some examples of this embodiment, a step of compressing the mixed raw materials into tablets may be included before calcination. During the tableting process, the pressure applied to the mixed raw materials can be 2 MPa to 10 MPa.

[0058] As some examples of this embodiment, the calcination temperature can be controlled between 700°C and 900°C during the calcination process. For example, the calcination temperature can be controlled at 700°C, 720°C, 750°C, 780°C, 800°C, 820°C, 850°C, 880°C, or 900°C, or the calcination temperature can be controlled between any two of the above temperatures.

[0059] As some examples of this embodiment, the calcination time is controlled to be 10h to 15h during the calcination process. For example, the calcination time can be controlled to be 10h, 11h, 12h, 13h, 14h, or 15h, or the calcination time can be controlled between any two of the above times.

[0060] By using the above-mentioned calcination temperature and time, it is possible to ensure that the raw materials are fully combined and transformed into the required sodium manganese oxide.

[0061] Step S2 involves mixing the precursor material with an excess of the second lithium source and then performing ion exchange treatment to replace the sodium element in the precursor material with the lithium element.

[0062] It is understandable that during ion exchange treatment, lithium ions from the second lithium source replace sodium ions in the precursor material, thereby converting sodium manganese oxide into the desired lithium-rich manganese-based oxide. Excessive second lithium source refers to a situation where the amount of lithium in the second lithium source exceeds the amount of sodium in the precursor material.

[0063] As some examples of this embodiment, the steps of performing ion exchange treatment include: mixing the precursor material with a second lithium source and then heating it so that lithium ions in the second lithium source replace sodium ions in the precursor material.

[0064] As examples of this embodiment, the molar ratio of sodium in the precursor material to lithium in the second lithium source is 1:(5~15). For example, the molar ratio of sodium to lithium can be 1:5, 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, or 1:15, or the molar ratio of sodium to lithium can be between any two of the above ratios. By using this ratio of the second lithium source, it is possible to ensure that sodium ions in the precursor material are replaced by lithium ions as fully as possible, thereby improving the purity of the formed lithium-rich manganese-based oxide.

[0065] As some examples of this embodiment, the second lithium source is selected from one or more of lithium nitrate and lithium chloride. By using lithium nitrate and lithium chloride as the second lithium source, it is beneficial to maintain the integrity of the sodium manganese oxide lattice during ion exchange and to avoid the introduction of impurity elements.

[0066] As some examples of this embodiment, the second lithium source can be a mixture of lithium nitrate and lithium chloride. The amount of lithium nitrate can be greater than the amount of lithium chloride. For example, the molar ratio of lithium nitrate to lithium chloride can be (80~95):(5~20).

[0067] As some examples of this embodiment, in the step of heating the precursor material and the second lithium source, the heating temperature can be controlled to be 280°C to 360°C. For example, the heating temperature can be controlled to be 280°C, 290°C, 300°C, 310°C, 320°C, 330°C, 340°C, 350°C, or 360°C, or the heating temperature can be controlled to be within any two of the above temperatures.

[0068] As some examples of this embodiment, in the step of heating the precursor material and the second lithium source, the heating time can be controlled to be 3h to 6h. For example, the heating time can be controlled to be 3h, 3.5h, 4h, 4.5h, 5h, 5.5h, or 6h, or the heating time can be controlled within any two of the above times.

[0069] By using the above heating temperature and heating time, it is possible to ensure that the sodium ions in the precursor material are replaced as fully as possible by the lithium ions in the second lithium source.

[0070] As some examples of this embodiment, after mixing the precursor material with an excess of a second lithium source and performing ion exchange treatment, the resulting product may also include steps of washing with water, centrifuging precipitation, and drying to remove impurities and separate the lithium-rich manganese-based oxide.

[0071] Thirdly, this disclosure also provides a cathode material comprising lithium-rich manganese-based oxide as described in the above embodiments.

[0072] It is understandable that this lithium-rich manganese-based oxide can serve as the active material in the cathode material. The cathode material may also include other auxiliary materials.

[0073] As some examples of this embodiment, the cathode material may further include at least one of a conductive agent and a binder. Further, the conductive agent may include one or more of conductive carbon black, acetylene black, carbon fiber, carbon nanotubes, and graphene. The binder may include polyvinylidene fluoride (PVDF).

[0074] The cathode material in this embodiment can be the cathode material of a lithium-ion battery.

[0075] Fourthly, this disclosure also provides a battery comprising a positive electrode, a negative electrode, and an electrolyte, wherein the positive and negative electrodes are disposed opposite to and spaced apart, the electrolyte is disposed between the positive and negative electrodes, and the positive electrode comprises a lithium-rich manganese-based oxide as described in any of the above embodiments.

[0076] It is understood that this battery can be a lithium-ion battery. In this battery, the electrolyte can be a solid electrolyte or a liquid electrolyte. When the electrolyte is a liquid electrolyte, the battery may also include a separator.

[0077] Furthermore, this disclosure provides the following specific embodiments and comparative examples to further illustrate the specific implementation of this disclosure and its advantages.

[0078] Example 1

[0079] Li₂CO₃, Na₂CO₃, MnCO₃, and MgO were prepared in a molar ratio of Li:Na:Mn:Mg = 0.15:0.6:0.8:0.05 and placed in a ball mill jar. Ethanol was used as the liquid medium, and the mixture was ball-milled at 300 rpm for 4 hours.

[0080] The ball-milled mixture was compressed into tablets under a pressure of 4 MPa, then placed in a muffle furnace and heated to 750 °C at a heating rate of 5 °C / min in air atmosphere, and held at 750 °C for 12 h. After the holding period, it was naturally cooled to room temperature to form sodium manganese oxide as a precursor material.

[0081] A mixture of LiNO3 and LiCl in a molar ratio of 88:12 was used as the second lithium source. The second lithium source was mixed with the aforementioned precursor material in a lithium to sodium molar ratio of 10:1, and then ball-milled. After ball milling, the mixture was placed in a muffle furnace and heated to 320°C at a heating rate of 5°C / min under air atmosphere, and held at that temperature for 4 hours. After the holding period, it was cooled to room temperature at a cooling rate of 5°C / min.

[0082] The cooled material was washed with water, centrifuged to precipitate, and then dried to form a lithium-rich manganese-based oxide with the chemical formula Li. 0.6 [Li 0.15 Mg 0.05 Mn 0.8 O2.

[0083] Example 2

[0084] Example 2 is prepared in a manner similar to Example 1, with the main difference being that Al2O3 is used instead of MgO in Example 2. Li2CO3, Na2CO3, MnCO3, and Al2O3 are mixed in a molar ratio of Li:Na:Mn:Al = 0.15:0.6:0.8:0.05. The final product of Example 2 has the chemical formula Li. 0.6 [Li 0.15 Al 0.05 Mn 0.8 O2.

[0085] Example 3

[0086] Example 3 was prepared in a manner similar to Example 1, with the main difference being that TiO2 was used instead of MgO in Example 3. Li2CO3, Na2CO3, MnCO3, and TiO2 were mixed in a molar ratio of Li:Na:Mn:Ti = 0.15:0.6:0.8:0.05. The final product of Example 3 has the chemical formula Li. 0.6 [Li 0.15 Ti 0.05 Mn0.8 O2.

[0087] Example 4

[0088] Example 4 was prepared in a manner essentially the same as Example 1, the main difference being that Example 4 used GeO2 instead of MgO as a raw material, with Li2CO3, Na2CO3, MnCO3, and GeO2 mixed in a molar ratio of Li:Na:Mn:Ge = 0.15:0.6:0.8:0.05. The chemical formula of the final product in Example 4 is Li 0.6 [Li 0.15 Ge 0.05 Mn 0.8 O2.

[0089] Example 5

[0090] Example 5 was prepared in a manner essentially the same as Example 1, the main difference being that Example 5 used both MgO and Al2O3 as raw materials, with Li2CO3, Na2CO3, MnCO3, MgO, and Al2O3 mixed in a molar ratio of Li:Na:Mn:Mg:Al = 0.15:0.6:0.8:0.02:0.03. The final product of Example 5 has the chemical formula Li. 0.6 [Li 0.15 Al 0.03 Mg 0.02 Mn 0.8 O2.

[0091] Example 6

[0092] The preparation method of Example 6 is basically the same as that of Example 1, the main difference being that in Example 7, Li₂CO₃, Na₂CO₃, MnCO₃, and MgO are prepared in a molar ratio of Li:Na:Mn:Mg = 0.15:0.7:0.8:0.05. The chemical formula of the final product of Example 7 is Li 0.7 [Li 0.15 Mg 0.05 Mn 0.8 O2.

[0093] Example 7

[0094] The preparation method of Example 7 is basically the same as that of Example 1, the main difference being that in Example 8, Li₂CO₃, Na₂CO₃, MnCO₃, and MgO are prepared in a molar ratio of Li:Na:Mn:Mg = 0.15:0.8:0.8:0.05. The chemical formula of the final product of Example 7 is Li 0.8 [Li 0.15 Mg 0.05 Mn 0.8 O2.

[0095] Comparative Example 1

[0096] The preparation method of Comparative Example 1 is basically the same as that of Example 1, the main difference being that Comparative Example 1 does not use MgO as a raw material, but instead uses Li₂CO₃, Na₂CO₃, and MnCO₃ in a molar ratio of Li:Na:Mn = 0.25:0.6:0.75. The chemical formula of the final product of Comparative Example 1 is Li 0.6 [Li 0.25 Mn 0.75 O2.

[0097] Comparative Example 2

[0098] Comparative Example 2 was prepared in a manner essentially the same as that of Example 1, the main difference being that MgO was not used as a raw material in Comparative Example 2. Instead, Li₂CO₃, Na₂CO₃, and MnCO₃ were mixed in a molar ratio of Li:Na:Mn = 0.25:0.7:0.75. The chemical formula of the final product of Comparative Example 2 is Li 0.7 [Li 0.25 Mn 0.75 O2.

[0099] Comparative Example 3

[0100] Comparative Example 3 was prepared in a manner essentially the same as that of Example 1, the main difference being that MgO was not used as a raw material in the comparative example; instead, Li₂CO₃, Na₂CO₃, and MnCO₃ were mixed in a molar ratio of Li:Na:Mn = 0.2:0.7:0.8. The chemical formula of the final product of Comparative Example 3 is Li 0.7 [Li 0.2 Mn 0.8 O2.

[0101] Comparative Example 4

[0102] Comparative Example 4 was prepared in a manner essentially the same as Example 1, the main difference being that MgO was not used as a raw material in the comparative example; instead, Li₂CO₃, Na₂CO₃, and MnCO₃ were mixed in a molar ratio of Li:Na:Mn = 0.2:0.8:0.8. The final product of Comparative Example 4 has the chemical formula Li. 0.8 [Li 0.2 Mn 0.8 O2.

[0103] Comparative Example 5

[0104] Comparative Example 5 was prepared in a manner essentially the same as that of Example 1, the main difference being that Li₂CO₃, Na₂CO₃, MnCO₃, and MgO were prepared in a molar ratio of Li:Na:Mn:Mg = 0.2:0.6:0.75:0.05. The final product of Comparative Example 4 has the chemical formula Li. 0.6 [Li0.2 Mg 0.05 Mn 0.75 O2.

[0105] Experiment 1: The morphology of Example 1 was tested using a scanning electron microscope. A schematic diagram of the morphology of Example 1 can be seen in [reference needed]. Figure 1 .

[0106] Experiment 2: X-ray diffraction tests were performed on the material prepared in Example 1. The test patterns can be seen in... Figure 2 . Figure 2 The asterisk (*) indicates that the location of the asterisk corresponds to a diffraction peak in the superlattice structure.

[0107] Experiment 3: Using the materials prepared in each example and comparative example as the positive electrode active material, a slurry was formed by mixing and dispersing the positive electrode active material, conductive carbon black, and polyvinylidene fluoride in a mass ratio of 8:1:1 in N-methylpyrrolidone. The slurry was coated onto aluminum foil, dried, and cut into sheets to serve as the positive electrode sheet. A half-cell was assembled in a glove box using lithium metal as the counter electrode.

[0108] The rate performance of the battery prepared in Example 1 was tested at current densities of 0.1C, 0.2C, 0.5C, 1C, and 2C. The results are shown in [the table / document / etc.]. Figure 3 The test conditions were: electrochemical window of 1.5V~4.8V, current density 1C=200mA / g.

[0109] The battery prepared in Example 1 was subjected to two charge-discharge cycles at a current density of 0.1C. The first and second discharge curves can be seen in... Figure 4 , Figure 4 In the text, "1st" represents the first charge-discharge curve, and "2nd" represents the second charge-discharge curve.

[0110] The batteries prepared in each example and comparative example were activated by cycling twice at a current density of 0.5C, and then subjected to 100 charge-discharge cycles at 0.2C. The initial discharge specific capacity, cycle retention rate, and voltage decay performance were tested, and the results are shown in Table 1. The test conditions were: electrochemical window of 1.5V~4.8V, current density 1C=200mA / g.

[0111] Table 1

[0112]

[0113] Referring to Table 1, Comparative Examples 1 to 4 did not introduce any doped metal elements, and the voltage decay of the batteries was above 0.19 mV / cycle, while the initial discharge specific capacity was only below 183 mAh / g. Although Comparative Example 5 introduced doped metal elements, the manganese content was low, while the total content of lithium and doped elements (in brackets) was high, resulting in a still high voltage decay. In contrast, Examples 1 to 7 all used doped metal elements with a stoichiometric ratio below 0.2, and the overall voltage decay of the batteries was below 0.12 mV / cycle, with an initial discharge specific capacity exceeding 200 mAh / g. This demonstrates that the lithium-rich manganese-based oxide of this disclosure can effectively improve the discharge specific capacity of the battery and reduce voltage decay during cycling.

[0114] Furthermore, referring to Examples 1-5, Examples 1, 2, and 5 exhibit better initial discharge specific capacity, cycle retention, and voltage decay, indicating that using Mg and / or aluminum as doping elements in the chemical formula of this disclosure can further improve the battery's discharge performance. Referring to Examples 1 and 6-7, when the stoichiometry of lithium (the value of m in this disclosure) is higher than 0.7, the battery's cycle performance shows a significant decrease. Therefore, using a lithium-rich manganese-based oxide with m < 0.7 can ensure good battery cycle performance.

[0115] Please note that the above embodiments are for illustrative purposes only and are not intended to limit the scope of this document.

[0116] It should be understood that, unless otherwise expressly stated herein, there is no strict order in which the steps are performed, and these steps may be performed in other orders. Moreover, at least some steps in the preparation process may include multiple sub-steps or multiple stages, which are not necessarily completed at the same time, but may be performed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but may be performed alternately or in turn with other steps or at least some of the sub-steps or stages of other steps.

[0117] 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.

[0118] 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.

Claims

1. A lithium-rich manganese-based oxide, characterized in that, The lithium-rich manganese-based oxide has O2 phase crystal structure characteristics, and a chemical formula of Li m [Li 0.2-x T x ]Mn 0.8 O2, wherein 0.6≤m≤0.8, 0 The lithium-rich manganese-based oxide has a superlattice structure.

2. The lithium-rich manganese-based oxide according to claim 1, characterized in that, The chemical formula of the lithium-rich manganese-based oxide is Li m [Li 0.2-x Mg x Mn 0.8 O2.

3. The lithium-rich manganese-based oxide according to claim 2, characterized in that, The chemical formula of the lithium-rich manganese-based oxide is Li m [Li 0.15 Mg 0.05 Mn 0.8 O2, Li m [Li 0.1 Mg 0.1 Mn 0.8 O2 or Li m [Li 0.05 Mg 0.15 Mn 0.8 O2.

4. The lithium-rich manganese-based oxide according to any one of claims 1 to 3, characterized in that, The lithium-rich manganese-based oxide is in the form of primary particles, and the particle size of the lithium-rich manganese-based oxide is ≤2μm.

5. The lithium-rich manganese-based oxide according to any one of claims 1 to 3, characterized in that, In the X-ray diffraction characterization pattern of the lithium-rich manganese-based oxide, there are diffraction peaks corresponding to the superlattice structure between 21° and 25°.

6. The method for preparing lithium-rich manganese-based oxides according to any one of claims 1 to 5, characterized in that, Includes the following steps: Sodium source, first lithium source, doped metal source and manganese source are mixed in a ratio of m:(0.2-x):x:0.8 and then calcined to form a precursor material, wherein the doped metal source contains the doped metal element; The precursor material is mixed with an excess of a second lithium source and then subjected to ion exchange treatment, so that the sodium element in the precursor material is replaced with lithium element.

7. The method for preparing lithium-rich manganese-based oxide according to claim 6, characterized in that, The sodium source, the first lithium source, the doped metal source, and the manganese source satisfy at least one of the following characteristics (1) to (4): (1) The sodium source is selected from one or more of sodium hydroxide, sodium carbonate, and sodium oxide; (2) The first lithium source is selected from one or more of lithium hydroxide, lithium carbonate, and lithium oxide; (3) The doped metal source is selected from the oxide of the doped metal element; (4) The manganese source is selected from one or more of manganese carbonate, manganese dioxide, basic manganese oxide, manganese monoxide and manganese tetroxide.

8. The method for preparing lithium-rich manganese-based oxides according to claim 6 or 7, characterized in that, During the calcination process, the calcination temperature is controlled at 700℃~900℃, and the calcination time is controlled at 10h~15h; and / or, The second lithium source is selected from one or more of lithium nitrate and lithium chloride. The molar ratio of sodium in the precursor material to lithium in the second lithium source is 1:(5~15). The ion exchange treatment step includes: mixing the precursor material with the second lithium source and heating it to 280℃~360℃, and maintaining it for 3h~6h.

9. A positive electrode material, characterized in that, Including the lithium-rich manganese-based oxide as described in any one of claims 1 to 5.

10. A battery, characterized in that, The device includes a positive electrode, a negative electrode, and an electrolyte, wherein the positive electrode and the negative electrode are disposed opposite to each other and spaced apart, and the electrolyte is disposed between the positive electrode and the negative electrode, wherein the positive electrode comprises a lithium-rich manganese-based oxide as described in any one of claims 1 to 5.

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