A high-rate p2-type sodium-ion battery layered cathode material and a preparation method thereof

Abstract

The application discloses a high-rate P2-type sodium-ion battery layered positive electrode material, chemical formula is Na x A a B b Ni 0.36‑a‑b Mn 0.67‑ c C c O 2‑d‑2e D d E e , wherein, in the chemical formula, 0.67<=x<=0.85, 0 ‑ ; E is S 2‑ . The application considers different functions of elements, effectively inhibits sodium / vacancy order in the charging and discharging process by using synergistic effect of multiple elements, increases sodium layer spacing, improves diffusion rate in the sodium-ion charging and discharging process, and further obtains a positive electrode material with excellent rate performance.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery cathode material technology, and in particular to a high-rate P2 type sodium-ion battery layered cathode material and its preparation method. Background Technology

[0002] Lithium-ion batteries have been widely used in portable energy storage devices due to their advantages such as high safety, long lifespan, and high energy density. However, the uneven distribution and increasingly high price of lithium resources hinder the further application of lithium batteries, especially in large-scale energy storage. Sodium-ion batteries operate on the same principle as lithium-ion batteries, and due to their low cost and abundant sodium resources, they have become one of the most promising candidates for large-scale energy storage applications and low-speed electric vehicles. The cathode material, as a key component of sodium-ion batteries, has a significant impact on their electrochemical performance.

[0003] Layered metal oxides have attracted widespread attention from researchers due to their advantages such as high specific capacity and operating voltage, ease of preparation, environmental friendliness and non-toxicity, and low cost. Layered transition metal oxide cathode materials for sodium-ion batteries can be classified into P2 type and O3 type based on the arrangement and stacking order of oxygen atoms, among which Na... + The triangular prism and octahedral positions occupying the sodium layer (NaO2) distinguish between the P-type and O-type structures. Compared to the O3 phase structure, the P2 phase structure exhibits higher ionic conductivity and a lower diffusion barrier. Therefore, P2-type layered oxides are a highly promising cathode material for sodium-ion batteries.

[0004] However, the commercial application of P2-type layered oxides is still limited by the following two aspects. On the one hand, due to Na... + With a large radius, due to Na + The insertion and extraction of Na can lead to complex phase transition processes in layered materials, resulting in Na… + The diffusion kinetics deteriorate, and on the other hand, its unique site occupancy mode and strong Na+ + -Na + Electrostatic interactions cause the material to exhibit a significant ordered arrangement of sodium / vacancy sites in the sodium layer, which reduces its diffusion rate. Therefore, suppressing the ordered arrangement of sodium / vacancy sites in the sodium layer and improving the cycle and rate performance of the material are crucial for promoting the industrialization of sodium-ion batteries.

[0005] Surface coating, structural design, and elemental doping are common methods to improve the cycle performance of cathode materials. For example, patent document CN114388794A discloses an aluminum-doped zinc oxide-coated sodium nickel manganate cathode material. Coating the sodium surface with highly conductive aluminum-doped zinc oxide can reduce the contact between the cathode material and the electrolyte, suppress side reactions, improve the cycle performance of the material, and simultaneously address the material's poor conductivity, thus enhancing rate performance. Liu et al. controlled the Nae / Naf ratio by increasing the sodium content, synthesizing Na... 0.696 Ni 0.329 Mn 0.671 O2 still has a capacity of 54.33 mAh g at 50°C. -1 The discharge capacity was [not specified in the original text]. However, surface coating and structural design strategies still failed to completely solve the problem of sodium vacancy ordering during charging and discharging. Wang et al. chose to [not specified in the original text] with Mn [not specified in the original text]. 4+ Ti with similar ionic radii but different Fermi levels 4+ To suppress the ordered arrangement of sodium vacancies, Ti 4+ After substitution, the electrons in the transition metal layer become localized, resulting in the prepared P2-Na 2 / 3Ni 1 / 3 Mn 1 / 3 Ti 1 / 3 O2 exhibits a solid solution ramp curve and demonstrates excellent rate performance, retaining 77.5% of its initial capacity at high rates (20C) (Sci. Adv. 2018, 4, eaar6018.). Xiao et al. synthesized a stable Na... 2 / 3 Ni 1 / 6Mn 2 / 3 Cu 1 / 9 Mg 1 / 18 The O2 cathode material consists of multilayered, oriented stacked nanosheets, in which nickel sites are replaced by copper and magnesium. On one hand, a chemical element substitution strategy is used to replace Na... + The quasi-solid solution reaction involving extraction / intercalation transforms into an absolute solid solution reaction; on the other hand, the multilayered oriented nanosheet structure, due to its increased electrode-electrolyte contact area and shorter diffusion distance, can effectively promote the reaction of Na+. + The electrode exhibits excellent transport kinetics and retains 73% of its capacity at 30C (Adv. Energy Mater. 2019, 1803978). However, the capacities of the aforementioned materials are all below 90 mAh / g, and this low capacity cannot meet the commercialization requirements of batteries.

[0006] Although the above methods have achieved some success in improving the rate of expansion, current research techniques still have problems such as low capacity, reversible phase difference in structure, failure to suppress sodium vacancy ordering, and complex preparation processes, which hinder large-scale application. Summary of the Invention

[0007] The purpose of this invention is to provide a high-rate layered cathode material for sodium-ion batteries and its preparation method. Considering the different functions of elements, the synergistic effect of multiple elements effectively suppresses sodium / vacancy ordering during charge and discharge, increases the sodium interlayer spacing, improves the diffusion rate of sodium ions during charge and discharge, and solves the problems of structural instability and poor rate performance of P2-type layered oxide cathodes in sodium-ion batteries during charge and discharge cycles.

[0008] To achieve the above objectives, the present invention employs the following technical solution:

[0009] A high-rate P2 type sodium-ion battery layered cathode material, with the chemical formula Na x A a B b Ni 0.36-a-b Mn 0.67- c C c O 2-d-2e D d E e In the chemical formula, 0.67≤x≤0.85, 0<a≤0.05, 0<b≤0.10, 0.03≤c≤0.10, 0≤d≤0.05, 0≤e≤0.05, and 0<d+e≤0.05; metal ion A is selected from K + 、Rb + C S + 、Sr 2+ Ba 2+ At least one of them, wherein the B metal ion is selected from low-valence Li + Mg 2+ Cu 2+ Zn 2+ Fe 3+ Al 3+ One or more combinations thereof, wherein the C metal ion is selected from high-valence Ti 4+ Ce 4+ Sn 4+ Zr 4+ Sb 5+ Bi 5+ 、Nb 5+ Ta 5+ Mo 6+ W 6+ One of them; D is F - E is S2- .

[0010] Preferably, metal ion A is selected from Sr 2+ Ba 2 At least one of them, wherein the B metal ion is selected from low-valence Mg 2+ Zn 2+ At least one of them, wherein the C metal ion is selected from high-valence Ti 4+ Sn 4+ Zr 4+ At least one of the following; and 0.78≤x≤0.80, 0.03≤a≤0.04, 0.06≤b≤0.08, 0.05≤c≤0.07, 0.02≤d≤0.03, 0.01≤e≤0.02.

[0011] More preferably, the metal ion A is Srr 2+ B metal ions are selected from Mg 2+ Zn 2+ At least one of them, where the C metal ion is Ti 4+ .

[0012] In a preferred embodiment of the present invention, the high-rate P2 type sodium-ion battery layered cathode material has the chemical formula Na. 0.78 Sr 0.03 Zn 0.06 Ni 0.27 Mn 0.60 Ti 0.07 O 1.95 F 0.03 S 0.01 Na 0.78 Sr 0.03 Zn 0.06 Ni 0.27 Mn 0.60 Ti 0.0 7O 1.96 F 0.02 S 0.01 Na 0.78 Sr 0.03 Zn 0.03 Mg 0.03 Ni 0.27 Mn 0.60 Ti 0.07 O 1.95 F 0.03 S 0.01 Na 0.80 Sr 0.03 Zn 0.06 Ni 0.27 Mn 0.60 Ti 0.07 O 1.95 F 0.03 S0.01 or Na 0.78 Ba 0.02 Sr 0.01 Zn 0.06 Ni 0.27 Mn 0.60 Ti 0.07 O 1.95 F 0.05 .

[0013] This invention also provides a solid-state method for preparing the high-rate P2 type sodium-ion battery layered cathode material, comprising the following steps:

[0014] (1) Weigh the sodium-containing compound, nickel-containing compound, manganese-containing compound, and compound containing doped elements according to the molar ratio of each element in the layered cathode material of high-rate P2 type sodium-ion battery.

[0015] (2) Place each compound in an agate ball mill jar and mechanically mix them using ethanol as a dispersant;

[0016] (3) The mixed slurry is fed into a muffle furnace and pre-fired in an air atmosphere;

[0017] (4) The pre-calcined sample is thoroughly ground and pressed into round tablets using a tablet press;

[0018] (5) Place the pressed discs in a muffle furnace for secondary calcination, and grind them thoroughly after cooling in the furnace.

[0019] Further, in step (1), the sodium-containing compound is selected from one or more of sodium carbonate, sodium nitrate, sodium oxide, sodium peroxide, sodium hydroxide, sodium fluoride, and sodium sulfide; the nickel-containing compound is selected from one or more of nickel nitrate, nickel oxide, nickel hydroxide, and nickel acetate; the manganese-containing compound is selected from one or more of manganese carbonate, manganese nitrate, manganese dioxide, manganese trioxide, and manganese hydroxide; and the doped element compound is selected from one or more of oxides of doped elements, carbonate compounds, nitrate compounds, acetate compounds, hydroxides, and halides. If F and / or S are present in the layered cathode material of the high-rate P2 type sodium-ion battery, a certain proportion of sodium fluoride and / or sodium sulfide needs to be added.

[0020] Further, in step (2), the ball mill speed is 300-800 rpm and the rotation time is 4-8 h; in step (3), the first stage program temperature rises to 400-550℃ and then calcines for 4-6 h; in step (4), the tablet press pressure is 15-20 MPa and the disc diameter is 10-15 mm; in step (5), the second stage program temperature rises to 850-1000℃ and then calcines for 10-15 h.

[0021] This invention also provides a sol-gel method for preparing the high-rate P2 type sodium-ion battery layered cathode material, comprising the following steps:

[0022] (1) According to the molar ratio of each element in the layered cathode material of high-rate P2 sodium-ion battery, water-soluble sodium-containing compound, water-soluble nickel-containing compound, water-soluble manganese-containing compound, and water-soluble compound containing doped metal elements are dissolved in deionized water and then a chelating agent is added.

[0023] (2) Stir the solution obtained in step (1) at 60-90℃ for 4-8 hours to form a gel;

[0024] (3) The gel was placed in an oven at 60-120°C for 24-36 hours to obtain an intermediate product;

[0025] (4) The intermediate product is thoroughly ground and calcined in a muffle furnace in stages. After cooling, the positive electrode is obtained.

[0026] The chelating agent mentioned in step (1) is at least one of citric acid, malic acid, and hydroxyethylidene diphosphonic acid. The amount of chelating agent added is 2-4 times (e.g., 3 times) the molar mass of the metal ion. After adding the chelating agent, stir for 30-60 minutes under stirring conditions of 400-800 rpm.

[0027] Preferably, the chelating agent is a mixture of at least one of citric acid and malic acid and hydroxyethylidene diphosphonic acid in a molar ratio of 1-2:1. The inventors unexpectedly discovered that the chelating agent in the above-described mixture significantly improves the cycle stability of the resulting cathode material.

[0028] The dripping rate in step (1) is 2-5 mL / min; the calcination in step (4) is divided into two stages. In the first stage, the temperature is programmed to rise to 350-550℃ and then calcined for 4-8 hours. In the second stage, the temperature is programmed to rise to 850-950℃ and then calcined for 10-12 hours. Then the temperature is programmed to drop to 200-250℃, and the obtained positive electrode is immediately transferred to an argon-protected glove box for later use.

[0029] The present invention also provides the application of the high-rate P2 type sodium-ion battery layered cathode material in the preparation of sodium-ion battery cathode materials.

[0030] Preferably, the high-rate P2 type sodium-ion battery layered cathode material, conductive additives and binders are mixed in a mass ratio of 6-8:1-2:1-2 to form a slurry, which is then uniformly coated onto aluminum foil and dried to obtain the working electrode. The working electrode is then matched with metallic sodium to assemble a half cell.

[0031] More preferably, the conductive additive is Super P, and the binder is polyvinylidene fluoride.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] This invention provides a high-rate P2 type sodium-ion battery layered cathode material and its preparation method. The target layered cathode material is synthesized using a solid-state method or a sol-gel method. The preparation method is simple and efficient, and the raw materials used are non-toxic, harmless, inexpensive, and readily available. Considering the different functions of elements, the synergistic effect of multiple elements is utilized to effectively suppress sodium / vacancy ordering during charge and discharge, increasing the interlayer spacing of sodium layers and improving the diffusion rate of sodium ions during charge and discharge, thus obtaining a cathode material with excellent rate performance. This material exhibits excellent electrochemical performance during the charge and discharge reaction process within the test range of 2.5V to 4.2V. At a 0.1C rate test, the reversible discharge capacity is high, reaching 102 mAh g⁻¹. -1 The above-mentioned material retains over 90% of its capacity even after 300 cycles at 1C. In particular, this invention, through doping with low-valence metals, high-valence metals, and F / S, produces a P2-type sodium-ion battery layered cathode material with excellent rate performance. At a high rate of 10C, the discharge capacity of this layered cathode material can reach 85 mAh g⁻¹. -1 The above demonstrates practical potential for electrochemical applications. Attached Figure Description

[0034] Figure 1 Na obtained in Example 1 0.78 Sr 0.03 Zn 0.06 Ni 0.27 Mn 0.60 Ti 0.07 O 1.95 F 0.05 X-ray diffraction pattern.

[0035] Figure 2 Na obtained in Example 1 0.78 Sr 0.03 Zn 0.06 Ni 0.27 Mn 0.60 Ti 0.07 O 1.95 F 0.05 SEM image.

[0036] Figure 3 Na obtained in Example 1 0.78 Sr 0.03 Zn 0.06 Ni 0.27 Mn 0.60 Ti 0.07 O 1.95 F 0.05 The charge / discharge curves.

[0037] Figure 4 Na obtained for Comparative Example 1 0.78 Ni 0.33 Mn 0.67 Charge and discharge curves of O2.

[0038] Figure 5 Na obtained in Example 1 0.78 Sr 0.03 Zn 0.06 Ni 0.27 Mn 0.60 Ti 0.07 O 1.95 F 0.05 The resulting long cycle graph.

[0039] Figure 6 Na obtained in Example 1 0.78 Sr 0.03 Zn 0.06 Ni 0.27 Mn 0.60 Ti 0.07 O 1.95 F 0.05 The resulting ratio chart. Detailed Implementation

[0040] The present invention will be further described below with reference to specific embodiments.

[0041] Example 1

[0042] Sodium-ion battery layered cathode material Na 0.78 Sr 0.03 Zn 0.06 Ni 0.27 Mn 0.60 Ti 0.07 O 1.95 F 0.05 Preparation steps.

[0043] 0.39 mol sodium carbonate, 0.03 mol strontium carbonate, 0.06 mol zinc oxide, 0.27 mol nickel oxide, 0.30 mol manganese trioxide, 0.07 mol titanium dioxide, and 0.05 mol sodium fluoride powder were weighed and placed in an agate ball mill jar. Ethanol was used as the dispersant, and the mixture was mechanically mixed using a ball mill at 500 rpm for 6 hours. The milled sample was then dried in a 60°C oven to obtain a powder sample. The mixed powder was placed in a muffle furnace and calcined at 550°C for 6 hours, then naturally cooled to room temperature and thoroughly ground. The mixed powder sample was pressed into discs with a diameter of 12 mm using a tablet press at 16 MPa, calcined at 900°C for 15 hours, and then cooled in the furnace to 200°C to obtain the sodium-ion battery cathode material.

[0044] Figure 1 Na prepared in Example 1 of this invention 0.78 Sr 0.03 Zn 0.06 Ni 0.27 Mn 0.60 Ti 0.07 O 1.95 F 0.05 The XRD pattern of the layered cathode material for sodium-ion batteries shows that its structure is well classified as hexagonal with space group P63 / mmc. The diffraction peaks are sharp and there are no other obvious impurity peaks.

[0045] Figure 2 Na prepared in Example 1 of this invention 0.78 Sr 0.03 Zn 0.06 Ni 0.27 Mn 0.60 Ti 0.07 O 1.95 F 0.05 SEM images of layered cathode materials for sodium-ion batteries show that their morphology consists of plate-like particles with a particle size between 2 and 5 micrometers.

[0046] Examples 2-23, Comparative Examples 1-5

[0047] Sodium-ion battery layered cathode materials were prepared under the same conditions and methods as in Example 1, specifically by adjusting the element ratios according to the chemical formulas of the cathode materials in each example and comparative example.

[0048] Taking Example 12 as an example, a layered cathode material Na for sodium-ion batteries was prepared. 0.78 Sr 0.03 Zn 0.06 Ni 0.27 Mn 0.60 Ti 0.0 7O 1.95 F 0.03 S 0.01 .

[0049] Weigh out 0.365 mol sodium carbonate, 0.03 mol strontium carbonate, 0.06 mol zinc oxide, 0.27 mol nickel oxide, 0.30 mol manganese trioxide, 0.07 mol titanium dioxide, 0.03 mol sodium fluoride, and 0.01 mol sodium sulfide. The remaining steps are the same as in Example 1.

[0050] Taking Example 13 as an example, the preparation of Na, a layered cathode material for sodium-ion batteries, was carried out. 0.78 Sr 0.03 Zn 0.06 Ni 0.27 Mn 0.60 Ti 0.07 O1.96 F 0.02 S 0.01 .

[0051] Weigh out 0.37 mol sodium carbonate, 0.03 mol strontium carbonate, 0.03 mol zinc oxide, 0.03 mol magnesium oxide, 0.27 mol nickel oxide, 0.30 mol manganese trioxide, 0.07 mol titanium dioxide, 0.02 mol sodium fluoride, and 0.01 mol sodium sulfide. The remaining steps are the same as in Example 1.

[0052] Taking Example 14 as an example, the layered cathode material Na for sodium-ion batteries was prepared. 0.78 Sr 0.03 Zn 0.03 Mg 0.03 Ni 0.27 Mn 0.60 Ti 0.07 O 1.95 F 0.03 S 0.01 .

[0053] Weigh out 0.365 mol sodium carbonate, 0.03 mol strontium carbonate, 0.03 mol zinc oxide, 0.03 mol magnesium oxide, 0.27 mol nickel oxide, 0.30 mol manganese trioxide, 0.07 mol titanium dioxide, 0.03 mol sodium fluoride, and 0.01 mol sodium sulfide. The remaining steps are the same as in Example 1.

[0054] Taking Example 15 as an example, the preparation of Na, a layered cathode material for sodium-ion batteries, was carried out. 0.80 Sr 0.03 Zn 0.06 Ni 0.27 Mn 0.60 Ti 0.07 O 1.95 F 0.03 S 0.01 .

[0055] The other conditions and operations are the same as in Example 12, except that the amount of sodium carbonate is changed to 0.4 mol.

[0056] Taking Example 16 as an example, the preparation of Na, a layered cathode material for sodium-ion batteries, was carried out. 0.78 Sr 0.03 Zn 0.06 Ni 0.27 Mn 0.62 Ti 0.05 O 1.95 F 0.03 S 0.01 .

[0057] Weigh out 0.365 mol sodium carbonate, 0.03 mol strontium carbonate, 0.03 mol zinc oxide, 0.03 mol magnesium oxide, 0.27 mol nickel oxide, 0.31 mol manganese trioxide, 0.05 mol titanium dioxide, 0.02 mol sodium fluoride, and 0.01 mol sodium sulfide. The remaining steps are the same as in Example 1.

[0058] Example 24

[0059] Preparation of Na by sol-gel method 0.78 Sr 0.03 Zn 0.06 Ni 0.27 Mn 0.60 Ti 0.07 O 1.95 F 0.03 S 0.01 .

[0060] (1) Sodium nitrate, strontium nitrate, zinc nitrate, nickel nitrate, manganese nitrate, tetrabutyl titanate, sodium fluoride, and sodium sulfide were dissolved in deionized water in a molar ratio of 0.73:0.03:0.06:0.27:0.60:0.07:0.03:0.01. Citric acid aqueous solution was added dropwise. The amount of citric acid used was three times the molar amount of metal ions in the precursor. After adding citric acid, stirring was continued for 40 min.

[0061] (2) Stir the solution obtained in step (1) at 70°C for 8 hours to form a precursor gel;

[0062] (3) The precursor gel was dried in an oven at 100°C for 24 hours to obtain the intermediate product;

[0063] (4) Grind the above product thoroughly and calcine it in a muffle furnace in stages. In the first stage, the temperature is increased to 450°C and calcined for 6 hours. In the second stage, the temperature is increased to 900°C and calcined for 12 hours. Then the temperature is decreased to 200°C. The obtained positive electrode is immediately transferred to an argon-protected glove box for later use.

[0064] Example 25

[0065] The other conditions are the same as in Example 24, except that the chelating agent is hydroxyethylidene diphosphonic acid.

[0066] Example 26

[0067] The other conditions are the same as in Example 24, except that the chelating agent is a mixture of citric acid and hydroxyethylidene diphosphonic acid in a molar ratio of 1:1.

[0068] Comparative Example 1

[0069] Sodium-ion battery layered cathode material Na 0.78 Ni0.33 Mn 0.67 O2 preparation steps.

[0070] Weigh out 0.39 mol sodium carbonate, 0.33 mol nickel oxide, and 0.335 mol manganese trioxide. The remaining steps are the same as in Example 1.

[0071] Comparative Example 2

[0072] Sodium-ion battery layered cathode material Na 0.78 Sr 0.03 Ni 0.33 Mn 0.67 O2 preparation steps.

[0073] Weigh out 0.335 mol sodium carbonate, 0.03 mol strontium carbonate, 0.33 mol nickel oxide, and 0.335 mol manganese trioxide, and follow the same steps as in Example 1.

[0074] Comparative Example 3

[0075] Sodium-ion battery layered cathode material Na 0.78 Zn 0.06 Ni 0.27 Mn 0.67 O2 preparation steps.

[0076] Weigh out 0.39 mol sodium carbonate, 0.06 mol zinc oxide, 0.27 mol nickel oxide, and 0.335 mol manganese trioxide, and follow the same steps as in Example 1.

[0077] Comparative Example 4

[0078] Sodium-ion battery layered cathode material Na 0.78 Ni 0.33 Mn 0.67 O 1.95 F 0.05 Preparation steps.

[0079] Weigh out 0.39 mol sodium carbonate, 0.33 mol nickel oxide, 0.335 mol manganese trioxide, and 0.05 mol sodium fluoride. The remaining steps are the same as in Example 1.

[0080] Comparative Example 5

[0081] Sodium-ion battery layered cathode material Na 0.78 Ni 0.33 Mn 0.60 Ti 0.07 O2 preparation steps.

[0082] Weigh out 0.39 mol sodium carbonate, 0.33 mol nickel oxide, 0.30 mol manganese trioxide, and 0.07 mol titanium dioxide. The remaining steps are the same as in Example 1.

[0083] Application examples

[0084] Sodium-ion battery assembly: Sodium-ion batteries were prepared using the cathode materials obtained in the sodium-ion battery cathode material preparation examples and comparative examples, following the steps below:

[0085] (1) The positive electrode material prepared in the above examples and comparative examples is mixed with Super P, binder polyvinylidene fluoride (PVDF) and conductive additive carbon black in a mass ratio of 80:10:10, and solvent N-methylpyrrolidone (NMP) is added. After slurry preparation, coating and drying processes, an electrode sheet with a diameter of 10 mm is obtained.

[0086] (2) The obtained positive electrode and the metallic sodium negative electrode were assembled into a sodium-ion battery. The electrolyte contained NaClO4 with a concentration of 1M. The solvent was a mixture of propylene carbonate (PC) and fluoroethylene carbonate (FEC) with a volume ratio of 95:5. The separator was a porous glass fiber membrane (whatman, GF / D). The CR2025 coin cell was assembled in an argon-filled glove box and electrochemical tests were performed.

[0087] Electrochemical performance testing:

[0088] The sodium-ion battery assembled in the sodium-ion battery assembly example was subjected to charge-discharge tests within a test voltage range of 2.5–4.2V (test current 0.1C, 1C = 100mAh g). -1 The test included cycle performance testing (test current 1C, 300 cycles) and charge / discharge performance testing at different rates (test currents of 0.1C, 0.5C, 1C, 5C, 10C, 20C, and 30C). The test results are shown in the table below.

[0089]

[0090]

[0091] As can be seen from the table, the sodium-ion battery cathode material in the examples exhibits better electrochemical performance compared to the comparative example. Figure 3 , 4 As can be seen, after introducing multiple doping elements, the sodium vacancy ordering and high-voltage phase transition during the charge and discharge process are significantly suppressed, thus exhibiting superior cycle performance and rate performance.

[0092] In particular, Examples 12-16 show that, in addition to doping with metal elements A, B, and C, simultaneous doping with F and S results in a cathode material with even better electrochemical performance.

[0093] The cathode materials prepared in Examples 12 and 24-26 all had the chemical formula Na. 0.78 Sr 0.03 Zn 0.06 Ni 0.27 Mn 0.60 Ti 0.07 O 1.95 F 0.03 S 0.01 The difference is that Example 12 uses the solid-phase method, while Examples 24-26 use the sol-gel method. It can be seen that the electrochemical performance of the cathode materials obtained by both the solid-phase and sol-gel methods is excellent. The sol-gel method, using only citric acid or hydroxyethylidene diphosphonic acid, has inferior electrochemical performance compared to the cathode material obtained by the solid-phase method in Example 12. However, Example 26, using a mixture of citric acid and hydroxyethylidene diphosphonic acid as a chelating agent, exhibits the best cycle stability.

[0094] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-rate P2 type sodium-ion battery layered cathode material, characterized in that, The chemical formula is Na x A a B b Ni 0.36-a- b Mn 0.67-c C c O 2-d-2e D d E e In the chemical formula, 0.78≤x≤0.80, 0.03≤a≤0.04, 0.06≤b≤0.08, 0.05≤c≤0.07, 0.02≤d≤0.03, and 0.01≤e≤0.02; the metal ion A is Sr. 2+ Ba 2+ At least one of them, wherein the B metal ion is selected from Mg 2+ Zn 2+ One or more combinations of the following, where the C metal ion is Ti 4+ D is F - E is S 2- ; The high-rate P2 type sodium-ion battery layered cathode material is prepared by the sol-gel method, including the following steps: (1) According to the molar ratio of each element in the layered cathode material of high-rate P2 sodium-ion battery, water-soluble sodium-containing compound, water-soluble nickel-containing compound, water-soluble manganese-containing compound, and water-soluble compound containing doped metal elements are dissolved in deionized water and then a chelating agent is added. (2) Stir the solution obtained in step (1) at 60-90℃ for 4-8 h to form a gel; (3) Place the gel in an oven at 60-120°C for 24-36 h to obtain an intermediate product; (4) The intermediate product is thoroughly ground and calcined in a muffle furnace in stages. After cooling, the positive electrode is obtained. The chelating agent mentioned in step (1) is a mixture of at least one of citric acid and malic acid and hydroxyethylidene diphosphonic acid in a molar ratio of 1-2:

1.

2. The high-rate P2 type sodium-ion battery layered cathode material according to claim 1, characterized in that, Chemistry is Na 0.78 Sr 0.03 Zn 0.06 Ni 0.27 Mn 0.60 Ti 0.07 The 1.95 F 0.03 S 0.01 、Na 0.78 Sr 0.03 Zn 0.06 Ni 0.27 Mn 0.60 Ti 0.07 The 1.96 F 0.0 2S 0.01 、Na 0.78 Sr 0.03 Zn 0.03 Mg 0.03 Ni 0.27 Mn 0.60 Ti 0.07 The 1.95 F 0.03 S 0.01 、orNa 0.80 Sr 0.03 Zn 0.06 Ni 0.27 Mn 0.60 Ti 0.07 The 1.95 F 0.03 S 0.01 。 3. The high-rate P2 type sodium-ion battery layered cathode material according to claim 1, characterized in that, In step (1), the amount of chelating agent added is 2-4 times the molar mass of the metal ions. After adding the chelating agent, stir for 30-60 min under stirring conditions of 400-800 rpm.

4. The high-rate P2 type sodium-ion battery layered cathode material according to claim 1, characterized in that, In step (1), the chelating agent is added at a rate of 2 to 5 mL / min. In step (4), the calcination is divided into two stages. In the first stage, the temperature is increased to 350 to 550°C and calcined for 4 to 8 hours. In the second stage, the temperature is increased to 850 to 950°C and calcined for 10 to 12 hours. Then, the temperature is decreased to 200 to 250°C. The obtained positive electrode is immediately transferred to an argon-protected glove box for later use.

5. The application of the high-rate P2 type sodium-ion battery layered cathode material as described in claim 1 or 2 in the preparation of sodium-ion battery cathode materials.

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