O3 phase material with oxygen-rich transition metal vacancies and preparation method and application thereof

Abstract

This invention discloses an oxygen-rich O3 phase material containing transition metal vacancies, its preparation method, and its applications, belonging to the field of sodium-ion battery technology; the chemical formula of the material of this invention is Na. x M y (Fe 0.5 Mn 0.5 ) 1‑y O 2+δ Wherein, M is a doped metal element, 0.8 ≤ x ≤ 1.0, 0 < y ≤ 0.4, δ > 0; the material exhibits oxygen-rich properties and contains transition metal vacancies in its crystal lattice. This invention effectively suppresses Mn doping by inducing transition metal vacancies through oxygen enrichment. 3+ The Jan Taylor effect significantly improves the cycle stability and structural stability of the cathode material. Furthermore, the cathode material of this invention does not contain expensive elements such as Ni and Co, resulting in low cost, and exhibits high discharge capacity within the 2-4V voltage range, making it suitable for large-scale energy storage applications.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, specifically relating to oxygen-rich O3 phase materials containing transition metal vacancies, their preparation methods, and applications. Background Technology

[0002] With the rapid development of the large-scale energy storage market, sodium-ion batteries (SIBs) are considered an important supplementary technology to lithium-ion batteries due to their advantages such as abundant sodium resources and low cost. However, the overall energy density of SIBs is relatively low, resulting in higher storage costs per kWh for SIBs using nickel-containing layered oxide cathodes, especially compared to lithium-ion battery systems using LiFePO4 cathodes. Therefore, developing nickel-free, low-cost, high-capacity sodium-ion layered cathodes is crucial for further reducing the storage cost per kWh of SIBs and enhancing their competitiveness. Therefore, NaFe, with Fe / Mn as the main component... 0.5 Mn 0.5 O2-based materials are among the most promising cathode materials, but they face key challenges affecting stability: Fe migration at high voltages (>4V) and the high-spin Mn... 3+ The resulting Ginger-Tyler distortion, due to Mn 3+ / Mn 4+ The redox potential is typically around 3.2 V (Vs.Na). + Below the Na group, if the capacity of Mn can be effectively utilized, the problems of Fe migration and electrolyte decomposition caused by pursuing capacity at higher voltages can be avoided; therefore, it is necessary to develop a system capable of operating within a narrow voltage range of 2~4V (vs. Na). + / Na) achieves high capacity while suppressing Mn 3+ The crystal distortion caused by the Ginger-Taylor effect is of great significance for achieving cathode materials with excellent cycle stability. Summary of the Invention

[0003] This invention provides oxygen-rich O3 phase materials containing transition metal vacancies, their preparation methods, and applications. A class of oxygen-rich O3 layered oxide materials containing transition metal vacancies were synthesized by solid-state sintering. The transition metal vacancies successfully suppressed the Ginger-Taylor distortion, achieving large capacity and excellent structural stability in a narrow voltage range.

[0004] To achieve the above objectives, the present invention adopts the following technical solution:

[0005] Oxygen-rich O3 phase materials containing transition metal vacancies, with Na x Fe 0.5 Mn 0.5 O2 is the main doped metal element with the chemical formula Na. x M y (Fe 0.5 Mn0.5 ) 1-y O 2+δ Where M is the doped metal, 0.8 ≤ x ≤ 1.0, 0<y ≤0.4,δ> 0.

[0006] The cathode material has oxygen-rich properties and contains transition metal vacancies in its crystal lattice, which are used to suppress Mn. 3+ The Ginger-Taylor distortion improves the positive electrode cycle stability.

[0007] Preferably, M is one or more of Li, Mg, Zn, Ti, Cu, Al, and Zr.

[0008] The preparation method of oxygen-rich O3 phase material containing transition metal vacancies, employing a one-step solid-state method or a two-step solid-state method, includes the following steps:

[0009] S1: Sodium source, doped metal source, iron source and manganese source are mixed according to the molar ratio of each element in the target product to obtain precursor powder;

[0010] S2: The precursor powder is sintered in an oxygen-containing atmosphere to obtain a sintered product; after cooling, the cathode material is obtained.

[0011] In the steps described above, the precursor powder is obtained by grinding or ball milling.

[0012] The sintering process involves calcining at 800~1000℃ for 15~20 hours, with a heating rate of 2~10℃ / min.

[0013] The cooling process is carried out in an oxygen-containing atmosphere or an oxygen-free atmosphere, with a cooling rate of 2~5℃ / min. After cooling in an oxygen-free atmosphere, heat treatment is required in an oxygen-containing atmosphere to release residual internal stress in the cathode material during the secondary sintering process. Preferably, the heat treatment process in an oxygen-containing atmosphere is as follows: the cooled product is tempered at 400~500℃ for 10~15 hours in an oxygen-containing atmosphere; wherein the oxygen-containing atmosphere is a mixed gas with an oxygen volume fraction of 2~10%.

[0014] The sodium source is selected from at least one of sodium carbonate, sodium hydroxide, and sodium peroxide.

[0015] The doped metal is one or more of Li, Mg, Zn, Ti, Cu, Al, and Zr; preferably one or more of Mg, Zn, Ti, Al, and Zr. The cathode material provided by this invention does not contain toxic and high-cost metal elements such as Ni and Co, and can even achieve true low-cost sustainability by being completely free of Li, Ni, Co, and Cu. The transition metal vacancies introduced through oxygen enrichment can suppress the Ginger-Taylor distortion and fully utilize Mn. 3+ / Mn 4+It provides capacity while achieving excellent cycle stability.

[0016] The aforementioned oxygen-rich O3 phase material containing transition metal vacancies can be used to prepare positive electrode sheets for sodium-ion batteries.

[0017] The sodium-ion battery operates in a narrow voltage range of 2-4V (vs. Na). + / Na) can provide 140~170mAh g -1 The discharge capacity achieves both low cost and high capacity, thereby reducing the cost per kWh of energy storage.

[0018] Beneficial effects: This invention provides oxygen-rich O3 phase materials containing transition metal vacancies, their preparation methods, and applications, which have the following advantages compared with existing technologies:

[0019] 1. This invention improves the material capacity and stability by introducing transition metal vacancies to suppress the Ginger-Taylor effect, and achieves the regulation of transition metal vacancy content by doping metals and controlling sintering conditions;

[0020] 2. This invention employs a one-step solid-state method or a two-step solid-state method. The one-step sintering method has a simple process; the two-step sintering method can release the residual internal stress in the cathode material during the secondary sintering process.

[0021] 3. In this invention, oxygen from the environment is adsorbed during the cooling process, transforming it into part of the positive electrode lattice oxygen. Simultaneously, this causes a rearrangement of transition metal layer atoms, forming transition metal vacancies. These transition metal vacancies can suppress Mn... 3+ The Ginger-Taylor effect causes crystal distortion, thereby improving the cycle stability of the positive electrode. Attached Figure Description

[0022] Figure 1 The X-ray diffraction (XRD) patterns are of the materials prepared in Comparative Example 1, Example 1, Example 2, Example 3 and Example 4.

[0023] Figure 2 The images show X-ray photoelectron spectroscopy (XPS) characterization of the materials prepared in Comparative Example 1, Example 1, and Example 2.

[0024] Figure 3 This is a graph showing the first constant current charge-discharge curve of a battery composed of materials prepared in Comparative Example 1, Example 1, Example 2, Example 3 and Example 4.

[0025] Figure 4 This is a constant current charge-discharge cycle diagram of a battery composed of materials prepared in Comparative Example 1, Example 1, and Example 2.

[0026] Figure 5This is a constant current charge-discharge cycle diagram of the battery composed of the materials prepared in Examples 3 and 4. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments:

[0028] Example 1

[0029] This embodiment prepares Na 0.8 Li 0.1 Fe 0.4 Mn 0.4 Ti 0.1 O 2.050 The specific steps are as follows:

[0030] Using Na2CO3, Li2CO3, Fe2O3, Mn2O3 and TiO2 as raw materials, after weighing them in a molar ratio of 8:1:4:4:2, the above raw materials are mixed evenly by ball milling.

[0031] The precursor powder was sintered in air at 850°C for 15 hours, and then cooled in the furnace to 200°C at a cooling rate of 2°C / min before being removed. It was then cooled to room temperature in an Ar atmosphere. The purpose of cooling in argon is that the cathode is prone to react with air and damage its structure at low temperatures. Cooling in argon can prevent the influence of air on the structure at low temperatures.

[0032] Example 2

[0033] This embodiment prepares Na 0.8 Li 0.1 Fe 0.4 Mn 0.4 Ti 0.1 O 2.025 The specific steps are as follows:

[0034] Using Na2CO3, Li2CO3, Fe2O3, Mn2O3 and TiO2 as raw materials, after weighing them in a molar ratio of 8:1:4:4:2, the above raw materials are mixed evenly by ball milling.

[0035] The precursor powder was sintered in air at 850°C for 15 hours, and immediately removed and cooled in an Ar atmosphere after sintering.

[0036] The powder was tempered at 500°C for 10 hours in a mixed atmosphere of 2% O2 / Ar, and then cooled in the furnace to 150°C before being taken out and cooled to room temperature in an Ar atmosphere.

[0037] Example 3

[0038] This embodiment prepares Na 0.8 Zn 0.1 Fe0.4 Mn 0.4 Ti 0.1 O 2.05 The specific steps are as follows:

[0039] Using Na2CO3, Zn(OH)2, Fe2O3, Mn2O3 and TiO2 as raw materials, after weighing them in a molar ratio of 4:1:2:2:1, the above raw materials are mixed evenly by ball milling.

[0040] The precursor powder was sintered in air at 850°C for 15 hours, and immediately removed and cooled in an Ar atmosphere after sintering.

[0041] The powder was tempered at 500°C for 10 hours in a mixed atmosphere of 2% O2 / Ar, and then cooled in the furnace to 150°C before being taken out and cooled to room temperature in an Ar atmosphere.

[0042] Example 4

[0043] This embodiment prepares Na 0.8 Zn 0.05 Mg 0.05 Fe 0.4 Mn 0.4 Ti 0.1 O 2.05 The specific steps are as follows:

[0044] Using Na2CO3, Zn(OH)2, MgO, Fe2O3, Mn2O3 and TiO2 as raw materials, after weighing them in a molar ratio of 8:1:1:4:4:2, the above raw materials are mixed evenly by ball milling.

[0045] The precursor powder was sintered in air at 850°C for 15 hours, and immediately removed and cooled in an Ar atmosphere after sintering.

[0046] The powder was tempered at 500°C for 10 hours in a mixed atmosphere of 2% O2 / Ar, and then cooled in the furnace to 150°C before being taken out and cooled to room temperature in an Ar atmosphere.

[0047] Compare with Example 1

[0048] Synthesize Na 0.8 Li 0.1 Fe 0.4 Mn 0.4 Ti 0.1 O2: Na2CO3, Li2CO3, Fe2O3, Mn2O3 and TiO2 are used as raw materials. After weighing them in a molar ratio of 8:1:4:4:2, the raw materials are mixed evenly by ball milling. Then the precursor powder is sintered in air at 850℃ for 15 hours. After sintering, it is immediately taken out and cooled in Ar atmosphere.

[0049] Figure 1 The XRD patterns show that five O3 layered cathode materials, namely, Control Example 1, Example 1, Example 2, Example 3 and Example 4, were successfully synthesized.

[0050] Figure 2 XPS showed that the valence states of Mn in Comparative Example 1, Example 1 and Example 2 were +3.75, +4 and +3.86, respectively. The valence states of Mn in Example 1 and Example 2 deviated from the theoretical value (+3.75), which may be related to the increase in the valence state of Mn due to oxygen enrichment.

[0051] The ICP-OES characterization of the materials is shown in Table 1:

[0052] Table 1. Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) Analysis of Comparative Examples 1, 1, and 2

[0053] Table 1 shows that the molar ratio of Na:Li:Fe:Mn:Ti is consistent with the experimental design, conforming to 8:1:4:4:1. Since the valence states of Na, Li, Fe, and Ti in the sodium ion layered cathode are relatively stable (+1, +1, +3, and +4 respectively), the chemical formula of the three materials can be determined as Na based on the valence states and ratios. 0.8 Li 0.1 Fe 0.4 Mn 0.4 Ti 0.1 O2, Na 0.8 Li 0.1 Fe 0.4 Mn 0.4 Ti 0.1 O 2.050 and Na 0.8 Li 0.1 Fe 0.4 Mn 0.4 Ti 0.1 O 2.025 In Examples 1 and 2, the oxygen ratio exceeded the normal stoichiometry, exhibiting an oxygen-rich state. This inevitably led to the rearrangement of transition metal layer atoms, generating transition metal vacancies. The calculated transition metal vacancy contents for Examples 1 and 2 were 0.024 and 0.012, respectively.

[0054] Electrochemical performance testing

[0055] Battery assembly: The positive electrode material, PVDF and acetylene black were mixed in NMP at a mass ratio of 8:1:1, ground evenly, and then coated onto an Al film. The mixture was then dried in a vacuum oven at 120°C. After drying, the film was cut into positive electrode sheets with a diameter of 12 mm. Sodium metal sheets, glass fiber membranes and 1M NaClO4 PC + 5% FEC were used as negative electrode separators and electrolytes, respectively, and assembled with the positive electrode sheets to form a coin cell. All of the above processes were completed in an argon glove box.

[0056] After battery assembly, it was left to stand for 8 hours, and then subjected to a current density of 20 mA g. -1 or 50 mA g -1 Constant current charge-discharge and cycle tests were performed within a voltage window of 2~4 V.

[0057] Figure 3 To compare the first charge-discharge curves of the five materials in Example 1, Example 1, Example 2, Example 3, and Example 4, the charging process is mainly driven by Mn. 3+ / Mn 4+ and Fe 3+ / Fe 4+ The redox reaction composition, in which Mn 3+ / Mn 4+ The redox reaction mainly occurs below ~3V, while Fe 3+ / Fe 4+ The oxidation-reduction principle is above ~3V. Comparative Example 1, Example 1, and Example 2 of Mn 3+ / Mn 4+ The redox reaction provides a capacity of 0.10e. - , 0 and 0.05e - This is consistent with the average valence state of Mn determined by XPS, so the average valence state of Mn can also be roughly determined through the first charging cycle curve. The Mn provided by the first charging cycle in Examples 3 and 4... 3+ / Mn 4+ The redox reaction capacities are all in the range of ~0.10e. - Therefore, the average valence state of Mn in these examples is around +3.75. Thus, the chemical formulas of Examples 3 and 4 are Na, respectively. 0.8 Zn 0.1 Fe 0.4 Mn 0.4 Ti 0.1 O 2.05 and Na 0.8 Zn 0.05 Mg 0.05 Fe 0.4 Mn 0.4 Ti 0.1 O 2.05The initial discharge capacity of the five materials was 154.65 mAh g, respectively. -1 144.82mAh g -1 153.10 mAh g -1 155.75 mAh g -1 and 167.81 mAh g -1 All exceed 140.00 mAh g -1 In particular, both cathodes in Examples 3 and 4 do not contain toxic or expensive elements such as Li, Ni, Co, and Cu, achieving true low cost and sustainable development. At the same time, they have ultra-high discharge capacity, which can effectively reduce the energy storage cost per kWh.

[0058] like Figure 4 As a control example 1, Examples 1 and 2 were tested at 50 mA g. -1 Cycling data at 2-4 V voltage range under high-rate conditions. In Control Example 1, the preparation method did not react with oxygen during cooling to form transition metal vacancies. Due to the lack of vacancies, its cycling performance was poor. Therefore, Control Example 1, which was not oxygen-rich (containing no transition metal vacancies), only achieved a capacity retention of 71.31% after 100 cycles. In contrast, the capacity retention of Examples 1 and 2, which were oxygen-rich (containing transition metal vacancies), reached as high as 84.96% and 85.61%, respectively. This indicates that the introduction of transition metal vacancies effectively suppressed Mn... 3+ The Ginger-Taylor distortion slowed down the structural degradation caused by Mn dissolution.

[0059] like Figure 5 Examples 3 and 4 were performed at 50 mA g. -1 At higher rates, the cycling data in the 2-4 V voltage range shows that after 100 cycles, the capacities of Examples 3 and 4 still remain at 93.81 mAh g⁻¹. -1 and 103.60 mAh g -1 The discharge capacity.

[0060] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An oxygen-rich O3 phase material containing transition metal vacancies, characterized in that, The chemical formula of the material is Na. x M y (Fe 0.5 Mn 0.5 ) 1-y O 2+δ Where M is a doped metal element, 0.8 ≤ x ≤ 1.0, 0 < y ≤ 0.4, δ > 0; the material has oxygen-rich properties and transition metal vacancies exist in the crystal lattice.

2. The oxygen-rich O3 phase material containing transition metal vacancies according to claim 1, characterized in that, The doped metal element M is one or more of Li, Mg, Zn, Ti, Cu, Al, and Zr.

3. The oxygen-rich O3 phase material containing transition metal vacancies according to claim 1 or 2, characterized in that, The doped metal element M is one or more of Mg, Zn, Ti, Al, and Zr.

4. The method for preparing the oxygen-rich O3 phase material containing transition metal vacancies according to any one of claims 1-3, characterized in that, Includes the following steps: S1: Mix sodium source, doped metal source, iron source and manganese source to obtain precursor powder; S2: The precursor powder is sintered in an oxygen-containing atmosphere to obtain a sintered product; After cooling, the oxygen-rich O3 phase material containing transition metal vacancies is obtained.

5. The method for preparing the oxygen-rich O3 phase material containing transition metal vacancies according to claim 4, characterized in that, The sintering process involves calcining at 800~1000℃ for 15~20 hours.

6. The method for preparing oxygen-rich O3 phase material containing transition metal vacancies according to claim 4, characterized in that, The cooling process can be carried out in an oxygen-containing atmosphere or an oxygen-free atmosphere; after cooling in an oxygen-free atmosphere, heat treatment is carried out in an oxygen-containing atmosphere; the cooling rate is 2~5℃ / min.

7. The method for preparing oxygen-rich O3 phase material containing transition metal vacancies according to claim 6, characterized in that, The heat treatment process in an oxygen-containing atmosphere is as follows: the cooled product is tempered at 400~500℃ for 10~15 hours in an oxygen-containing atmosphere.

8. The method for preparing oxygen-rich O3 phase material containing transition metal vacancies according to claim 4 or 7, characterized in that, The oxygen-containing atmosphere is a mixture of gases with an oxygen volume fraction of 2-10%.

9. The method for preparing the oxygen-rich O3 phase material containing transition metal vacancies according to claim 4, characterized in that, The sodium source is selected from at least one of sodium carbonate, sodium hydroxide, and sodium peroxide.

10. The application of the oxygen-rich O3 phase material containing transition metal vacancies as described in any one of claims 1-3, characterized in that, The material is used to prepare the positive electrode sheet for sodium-ion batteries; the sodium-ion battery has a capacity of 140-170 mAh g / L in a narrow voltage range of 2-4V. -1 The discharge capacity.

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