Manganese-based layered oxide with mixed structure and preparation method and application thereof

Abstract

This invention belongs to the field of sodium-ion battery materials and electrochemical technology, and provides a manganese-based substrate oxide with a mixed ordered and disordered structure, its preparation method, and its application. The chemical formula of this oxide is Na₁₋. x MᵧMn₁₋ᵧO₂ (0 < x < 1, 0 < y < 1, M is one or more elements such as Mg, Fe, Al, Zn, Co, Ni, Cu, etc.), belongs to the P2 phase and is composed of specific ordered (-Mn-Mn-M-) and disordered (-Mn-Mn-Mn-) structures. Its preparation method involves dissolving sodium salt, M salt, manganese salt, and an organic chelating agent in water in a specific ratio to prepare a precursor mixture. After heating to dryness, grinding, and sintering, the resulting oxide is obtained. As a positive electrode active material for sodium-ion batteries, this oxide significantly improves the capacity and reversibility of redox reactions compared to traditional materials, suppresses voltage decay, and enhances crystal structure stability. Its synthesis process is simple and low-cost, and it holds promise for applications in electric vehicles and large-scale energy storage, alleviating range and price issues.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery materials and electrochemical technology, specifically relating to a manganese-based base oxide with a mixed structure, its preparation method, and its application. Background Technology

[0002] Currently, lithium-ion batteries dominate the market for portable electronics and electric vehicles. However, due to increasing demand for lithium and concerns about its high cost, researchers are developing battery energy storage technologies based on new chemistry. Sodium-ion batteries are attracting attention due to their abundant resources, environmental friendliness, and low cost. Among them, layered oxide cathodes are currently one of the most commercially promising cathode materials for sodium-ion batteries.

[0003] Traditional layered oxide cathodes mainly rely on cations (such as Ni) 2+ Co 3+ Redox processes provide charge compensation to drive the overall electrochemical reaction and contribute to capacity. Recent studies have shown that utilizing reversible redox reactions with anions, such as oxygen ions rather than just cations, can effectively improve the theoretical capacity and energy density of batteries. However, such compounds (e.g., Na+) 2 / 3 Mg 1 / 3 Mn 2 / 3 Oxygen-redox reactions (O2) typically involve processes such as oxygen vacancy formation and O2 dimerization (2O2). 2- →O2 n- A series of problems arise, including O2 release, transition metal ion migration, phase transitions, and crack formation, leading to poor cycle stability, rapid voltage decay, and low safety in the materials. To mitigate these issues, several solutions have been proposed, such as interface engineering and elemental doping, to design and prepare cathode materials. However, these methods are often limited by complex synthesis steps, high costs, and unclear mechanisms. Therefore, designing highly stable and reversible anionic reactive metamorphic oxides using simple synthesis methods has become an urgent scientific problem to be solved. Summary of the Invention

[0004] The technical problem to be solved by this invention is to address the shortcomings of existing technologies by providing a method for preparing and applying a manganese-based substrate oxide with a mixed ordered and disordered structure. This method is applicable to the anionic oxidation-reduction of Na+. 2 / 3 M 1 / 3 Mn 2 / 3Based on O2, by simply adjusting the M / Mn chemical ratio, two different structural configurations are formed: an ordered configuration (-M-Mn-M-) and a disordered configuration (-Mn-Mn-Mn-). When used as a positive electrode active material for sodium-ion batteries, it exhibits extremely high specific capacity and minimal voltage decay. The stability and reversibility of the crystal structure and electrochemical reaction are significantly improved, effectively solving the aforementioned problems of anion-reactive positive electrodes. The manganese-based substrate oxide with a mixed ordered and disordered structure of this invention, as a positive electrode material for sodium-ion batteries, has a specific capacity exceeding 200 mAh g⁻¹. -1 Its high capacity and stable cycling voltage solve the dilemma of not being able to simultaneously achieve high capacity and stable voltage in anion-reactive cathodes. Its simple synthesis process and low cost make it a promising candidate for applications in electric vehicles and large-scale energy storage, alleviating range anxiety and price concerns.

[0005] To achieve the above objectives, the present invention provides a manganese-based crystalline oxide with a mixed structure, characterized in that the chemical formula of the manganese-based crystalline oxide is Na. 1-x M y Mn 1-y O2, 0 < x < 1, 0 < y < 1, belongs to the P2 phase, M is one or more of Mg, Fe, Al, Zn, Co, Ni, Cu, the mixed structure includes ordered structure and disordered structure, wherein in the ordered structure, two manganese atoms plus one M atom are arranged in the form of -M-Mn-M- as the basic repeating unit; in the disordered structure, the atoms are arranged in the form of continuous manganese atoms -Mn-Mn-Mn- as the basic repeating unit.

[0006] Furthermore, the average particle size of the manganese-based base oxide is 1~2μm, and the grain shape is plate-like.

[0007] The present invention also provides a method for preparing a manganese-based substrate oxide with a mixed structure as described above, characterized by comprising the following steps:

[0008] 1) Dissolve sodium salt, M salt, manganese salt and organic chelating agent in water and mix well to obtain precursor mixture;

[0009] 2) The precursor mixture is heated and evaporated to dryness to obtain the precursor;

[0010] 3) After grinding the precursor into powder, it is first pre-fired in air, and then sintered in air or oxygen atmosphere to obtain manganese base oxide with ordered and disordered mixed structure.

[0011] Furthermore, the sodium salt is one or more of anhydrous sodium nitrate, anhydrous sodium acetate, anhydrous sodium hydroxide, and sodium acetate trihydrate.

[0012] 5. The preparation method according to claim 3, wherein the M salt is one or more of anhydrous nitrate, anhydrous acetate, nitrate hexahydrate, and acetate tetrahydrate.

[0013] Furthermore, the manganese salt mentioned in step 1) is one or more of anhydrous manganese nitrate, anhydrous manganese acetate, manganese nitrate tetrahydrate, and manganese acetate tetrahydrate.

[0014] Furthermore, the organic chelating agent is one or more of citric acid and glycolic acid.

[0015] Furthermore, the molar ratio of the sodium salt, M salt, manganese salt, and organic chelating agent is (0.2-0.21):0.05:0.25:0.3; and the volume of water is 0.1-1L.

[0016] Furthermore, the heating temperature in step 2) is 70-95℃; the pre-firing temperature in step 3) is 400-550℃, and the pre-firing time is 2-6h; when the sintering temperature is 750-900℃, the sintering time is 10-20h.

[0017] The present invention also provides an application of the above-mentioned manganese base oxide with a mixed structure or the manganese base oxide prepared by the above method as a positive electrode active material for sodium-ion batteries.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] 1) This invention is the first to synthesize a manganese-based substrate oxide with a mixed ordered and disordered structure, comprising two structural units: an ordered configuration (-M-Mn-M-) and a disordered configuration (-Mn-Mn-Mn-). This achieves solid-solution mixing of configurations with different oxygen activities in three-dimensional space, avoiding excessive oxygen-oxidation reactions and regional concentration. When used as a positive electrode active material in sodium-ion batteries, it significantly enhances the capacity and reversibility contributed by redox reactions. Compared to other positive electrode materials involving oxygen redox reactions, this material exhibits higher redox capacity and better reversibility, a stable crystal structure, and significantly suppressed voltage decay caused by oxygen redox reactions.

[0020] 2) The modification process used in this invention is simple and easy to implement. Only by simply adjusting the chemical ratio of Mg / M can manganese base oxide with a mixed structure of ordered and disordered structures be obtained, avoiding the cumbersome and uncertain post-processing processes such as foreign ion doping or surface coating. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without creative effort. In the drawings:

[0022] Figure 1 The manganese base oxide Na with a mixed ordered and disordered structure prepared in Example 1 is 2 / 3 Mg 1 / 6 Mn 5 / 6 XRD pattern of O2 and its refined spectrum.

[0023] Figure 2 The manganese base oxide Na with a mixed ordered and disordered structure prepared in Example 1 is 2 / 3 Mg 1 / 6 Mn 5 / 6 SEM image of O2.

[0024] Figure 3 The manganese base oxide Na with a mixed ordered and disordered structure prepared in Example 1 is 2 / 3 Mg 1 / 6 Mn 5 / 6 X-ray energy dispersive spectrum of O2.

[0025] Figure 4 The manganese base oxide Na with a mixed ordered and disordered structure prepared in Example 1 is 2 / 3 Mg 1 / 6 Mn 5 / 6 O2 and common mono-ordered manganese base oxides Na 2 / 3 Mg 1 / 3 Mn 2 / 3 A comparison of charge-discharge curves with different numbers of cycles at 0.1C.

[0026] Figure 5 The manganese base oxide Na with a mixed ordered and disordered structure prepared in Example 1 is 2 / 3 Mg 1 / 6 Mn 5 / 6 O2 and common mono-ordered manganese base oxides Na 2 / 3 Mg 1 / 3 Mn 2 / 3 Capacity comparison chart after 50 cycles at 0.1°C.

[0027] Figure 6 The manganese base oxide Na with a mixed ordered and disordered structure prepared in Example 1 is 2 / 3 Mg 1 / 6 Mn 5 / 6O2 and common mono-ordered manganese base oxides Na 2 / 3 Mg 1 / 3 Mn 2 / 3 Comparison of discharge voltage equalization after 200 cycles under O21C.

[0028] Figure 7 The manganese base oxide Na with a mixed ordered and disordered structure prepared in Example 1 is 2 / 3 Mg 1 / 6 Mn 5 / 6 O2 and common mono-ordered manganese base oxides Na 2 / 3 Mg 1 / 3 Mn 2 / 3 Capacity comparison chart after 200 cycles under O21C.

[0029] Figure 8 The manganese base oxide Na with a mixed ordered and disordered structure prepared in Example 1 is 2 / 3 Mg 1 / 6 Mn 5 / 6 O2 and common mono-ordered manganese base oxides Na 2 / 3 Mg 1 / 3 Mn 2 / 3 Comparison of high-angle annular dark field images when O2 is charged to 4.5V. Detailed Implementation

[0030] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0031] It should be understood that, when used in this specification and the appended claims, the term "comprising" indicates the presence of a descriptive feature, integral, step, operation, element, and / or component, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components, and / or sets.

[0032] To keep the drawings concise, only the parts relevant to the invention are shown schematically in each figure, and they do not represent the actual structure of the product. Furthermore, for ease of understanding, in some figures, only one of components with the same structure or function is shown schematically, or only one is labeled. In this document, "one" can mean not only "only one" but also "more than one".

[0033] It should also be further understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0034] In the embodiments shown in the accompanying drawings, the directional indications (such as up, down, left, right, front, and back) used to explain the structure and movement of the various components of the invention are relative rather than absolute. These descriptions are appropriate when these components are in the positions shown in the drawings. If the descriptions of the positions of these components change, these directional indications also change accordingly.

[0035] Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0036] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the specific implementation of the present invention will be described below with reference to the accompanying drawings.

[0037] Example 1

[0038] A manganese-based base oxide with a mixed ordered and disordered structure is prepared by the following steps:

[0039] 1) Dissolve 0.2 mol anhydrous sodium acetate, 0.05 mol magnesium acetate tetrahydrate, 0.25 mol manganese acetate tetrahydrate and 0.3 mol citric acid in 0.3 L of water and mix well to obtain a precursor mixture;

[0040] 2) Heat the precursor mixture to 80°C and evaporate to dryness to obtain the precursor;

[0041] 3) After grinding the precursor into powder, it was pre-calcined in air at 450℃ for 4 h, and then sintered in air at 850℃ for 18 h to obtain a manganese base layer oxide Na with a mixed ordered and disordered structure. 2 / 3 Mg 1 / 6 Mn 5 / 6 O2.

[0042] Example 2

[0043] A manganese-based base oxide with a mixed ordered and disordered structure is prepared by the following steps:

[0044] 1) Dissolve 0.21 mol anhydrous sodium hydroxide, 0.05 mol magnesium acetate tetrahydrate, 0.25 mol manganese acetate tetrahydrate and 0.3 mol citric acid in 0.3 L of water and mix well to obtain a precursor mixture;

[0045] 2) Heat the precursor mixture to 90°C and evaporate to dryness to obtain the precursor;

[0046] 3) After grinding the precursor into powder, it was first pre-calcined in air at 500℃ for 2 h, and then sintered at 900℃ in an oxygen atmosphere for 10 h to obtain manganese base layer oxide Na with a mixed ordered and disordered structure. 2 / 3 Mg 1 / 6Mn 5 / 6 O2.

[0047] Example 3

[0048] A manganese-based base oxide with a mixed ordered and disordered structure is prepared by the following steps:

[0049] 1) Dissolve 0.2 mol sodium acetate trihydrate, 0.05 mol magnesium acetate tetrahydrate, 0.25 mol manganese acetate tetrahydrate and 0.5 mol glycolic acid in 0.3 L of water and mix well to obtain a precursor mixture;

[0050] 2) Heat the precursor mixture to 70°C and evaporate to dryness to obtain the precursor;

[0051] 3) After grinding the precursor into powder, it was first pre-calcined in air at 400℃ for 6 h, and then sintered at 800℃ in an oxygen atmosphere for 20 h to obtain manganese base layer oxide Na with a mixed ordered and disordered structure. 2 / 3 Mg 1 / 6 Mn 5 / 6 O2.

[0052] Example 4

[0053] A manganese-based base oxide with a mixed ordered and disordered structure is prepared by the following steps:

[0054] 1) Dissolve 0.2 mol anhydrous sodium nitrate, 0.05 mol anhydrous magnesium acetate, 0.25 mol anhydrous manganese nitrate and 0.3 mol glycolic acid in 0.3 L of water and mix well to obtain a precursor mixture;

[0055] 2) Heat the precursor mixture to 95°C and evaporate to dryness to obtain the precursor;

[0056] 3) After grinding the precursor into powder, it was first pre-calcined in air at 550℃ for 5 h, and then sintered at 750℃ in an oxygen atmosphere for 20 h to obtain manganese base layer oxide Na with a mixed ordered and disordered structure. 2 / 3 Mg 1 / 6 Mn 5 / 6 O2.

[0057] Figure 1 This is the XRD pattern and its refined image of the manganese base layer oxide with a mixed ordered and disordered structure prepared in this embodiment. The XRD pattern shows that the material belongs to the P2 phase. Further refinement reveals that it contains two phase structures: one is Na composed of ordered units -Mg-Mn-Mn. 2 / 3 Mg 1 / 3 Mn 2 / 3 The O2 phase is another phase consisting of Na composed of disordered units -Mn-Mn-Mn. 2 / 3The presence of the MnO2 phase, with a 4:1 ratio of the two phases, confirms the presence of Na. 2 / 3 Mg 1 / 6 Mn 5 / 6 O2 has a mixed structure of ordered and disordered elements.

[0058] Figure 2 This embodiment describes the preparation of a manganese-based base oxide, Na, with a mixed ordered and disordered structure. 2 / 3 Mg 1 / 6 Mn 5 / 6 SEM image of O2, showing plate-like grains with a grain size of 1~2μm.

[0059] Figure 3 This embodiment describes the preparation of a manganese-based base oxide, Na, with a mixed ordered and disordered structure. 2 / 3 Mg 1 / 6 Mn 5 / 6 The X-ray energy dispersive spectrum of O2 showed that the four elements Na, Mg, Mn and O were uniformly distributed throughout the particle.

[0060] The manganese base oxide Na with a mixed ordered and disordered structure prepared in this embodiment 2 / 3 Mg 1 / 6 Mn 5 / 6 O2 is used as the positive electrode active material in sodium-ion batteries and assembled into coin cells. The specific operation method is as follows: manganese-based base oxide Na with a mixed structure of ordered and disordered elements is used. 2 / 3 Mg 1 / 6 Mn 5 / 6 O2 is mixed with carbon black conductive agent and polyvinylidene fluoride (PVDF) binder at a mass ratio of 8:1:1 and dispersed in N-methylpyrrolidone (NMP) to form a slurry. The slurry is then uniformly coated on aluminum foil, dried, and cut into electrode sheets. These electrode sheets are then assembled with sodium sheets, glass fiber separators, and sodium electrolyte (1 mol / L NaPF6 dissolved in DMC / EC / DEC at a volume ratio of 1:1:1) to form a coin cell, and electrochemical performance is tested.

[0061] Figure 4 The manganese-based base oxide Na with a mixed ordered and disordered structure prepared in this embodiment is... 2 / 3 Mg 1 / 6 Mn 5 / 6 O2 and common mono-ordered manganese base oxides Na 2 / 3 Mg 1 / 3 Mn 2 / 3 A comparison of charge-discharge curves at O20.1C with different numbers of cycles. The graph shows that the capacities of both are comparable in the first cycle. As cycling progresses, Na... 2 / 3 Mg 1 / 3 Mn 2 / 3The charge / discharge curve of O2 changes continuously, and the original oxygen plateau disappears. As for Na... 2 / 3 Mg 1 / 6 Mn 5 / 6 For O2, the charge-discharge curves show little change, and the oxygen plateau remains even after 50 cycles. This indicates that the ordered-disordered mixed structure significantly improves the reversibility and stability of the oxygen-redox reaction process.

[0062] Figure 5 The example shows a manganese base oxide Na with a mixed ordered and disordered structure. 2 / 3 Mg 1 / 6 Mn 5 / 6 O2 and common mono-ordered manganese base oxides Na 2 / 3 Mg 1 / 3 Mn 2 / 3 Capacity comparison chart after 50 cycles at O20.1C. Throughout the process, Na... 2 / 3 Mg 1 / 6 Mn 5 / 6 O2 compared to Na 2 / 3 Mg 1 / 3 Mn 2 / 3 O2 has a higher capacity. Even after 50 cycles, it still has 186.21mAh g. -1 The extremely high capacity demonstrates the high reversibility and reactivity of the oxygen-oxidation reaction.

[0063] Figure 6 The manganese base oxide Na with a mixed ordered and disordered structure prepared in Example 1 is 2 / 3 Mg 1 / 6 Mn 5 / 6 O2 and common mono-ordered manganese base oxides Na 2 / 3 Mg 1 / 3 Mn 2 / 3 A comparison of discharge voltage equalization after 200 cycles at O21C. Similar to most anionic reactive layered oxides, Na... 2 / 3 Mg 1 / 3 Mn 2 / 3 O2 exhibits extremely rapid voltage decay, dropping from 2.60V to 2.28V. Na 2 / 3 Mg 1 / 6 Mn 5 / 6 The voltage drop of O2 is almost negligible, only 0.19mV per revolution. This indicates that the hybrid structure of ordered and disordered components can effectively solve the voltage drop problem.

[0064] Figure 7 The manganese base oxide Na with a mixed ordered and disordered structure prepared in Example 1 is 2 / 3 Mg 1 / 6 Mn 5 / 6O2 and common mono-ordered manganese base oxides Na 2 / 3 Mg 1 / 3 Mn 2 / 3 Capacity comparison chart after 200 cycles at O21C. At a higher current density (150 mAg)... -1 ), Na 2 / 3 Mg 1 / 6 Mn 5 / 6 O2 continues to demonstrate better stability and capacity retention.

[0065] Figure 8 The manganese base oxide Na with a mixed ordered and disordered structure prepared in Example 1 is 2 / 3 Mg 1 / 6 Mn 5 / 6 O2 and common mono-ordered manganese base oxides Na 2 / 3 Mg 1 / 3 Mn 2 / 3 Comparison of high-angle annular dark field images when O2 is charged to 4.5V. It can be seen that under high voltage, Na... 2 / 3 Mg 1 / 3 Mn 2 / 3 The structure of O2 was severely damaged, with numerous intragranular cracks appearing. Meanwhile, Na... 2 / 3 Mg 1 / 6 Mn 5 / 6 The O2 particles remained intact. This indicates that the mixed ordered and disordered structure effectively suppressed interlayer slip and lattice stress, thus enhancing the structural stability of the material.

[0066] The embodiments described above are some, but not all, embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A manganese-based base oxide with a mixed structure, characterized in that, The chemical formula of manganese base oxide is Na 2 / 3M 1 / 6 Mn 5 / 6 O2 belongs to the P2 phase, and M is one or more of Mg, Fe, Al, Zn, Co, Ni, and Cu. The mixed structure includes ordered and disordered structures. In the ordered structure, two manganese atoms plus one M atom are arranged in the form of -M-Mn-Mn- as the basic repeating unit. In the disordered structure, the atoms are arranged in the form of continuous manganese atoms -Mn-Mn-Mn- as the basic repeating unit.

2. The manganese-based base oxide with a mixed structure according to claim 1, characterized in that, The average particle size of the manganese base oxide is 2 μm, and the grain shape is plate-like.

3. A method for preparing a manganese-based substrate oxide with a mixed structure as described in claim 1 or 2, characterized in that, Includes the following steps: 1) Dissolve sodium salt, M salt, manganese salt and organic chelating agent in water and mix well to obtain precursor mixture; 2) The precursor mixture is heated and evaporated to dryness to obtain the precursor; 3) After grinding the precursor into powder, it is first pre-fired in air and then sintered in air or oxygen atmosphere to obtain manganese base layer oxide with ordered and disordered mixed structure.

4. The preparation method according to claim 3, characterized in that, The sodium salt is one or more of anhydrous sodium nitrate, anhydrous sodium acetate, anhydrous sodium hydroxide, and sodium acetate trihydrate.

5. The preparation method according to claim 3, characterized in that, The M salt is one or more of anhydrous nitrate, anhydrous acetate, nitrate hexahydrate, and acetate tetrahydrate.

6. The preparation method according to claim 3, characterized in that, Step 1) The manganese salt is one or more of anhydrous manganese nitrate, anhydrous manganese acetate, manganese nitrate tetrahydrate, and manganese acetate tetrahydrate.

7. The preparation method according to claim 3, characterized in that, The organic chelating agent is one or more of citric acid and glycolic acid.

8. The preparation method according to claim 3, characterized in that, The molar ratio of the sodium salt, M salt, manganese salt, and organic chelating agent is (0.2-0.21):0.05:0.25:0.3; the volume of water is 0.1-1L.

9. The preparation method according to claim 3, characterized in that, The heating temperature in step 2) is 70-95℃; the pre-firing temperature in step 3) is 400-550℃ and the pre-firing time is 2-6h; when the sintering temperature is 750-900℃, the sintering time is 10-20h.

10. The application of a manganese-based crystalline oxide with a mixed structure as described in claim 1 or 2, or a manganese-based crystalline oxide prepared by any one of claims 3-9, as a positive electrode active material for sodium-ion batteries.

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