High-rate P2-type sodium-ion battery layered positive electrode material and preparation method thereof

Abstract

The chemical formula of the high-rate P2 type sodium ion battery layered positive electrode material is NaxAaBbNi (0.36-a-b) Mn (0.67-c) CcO2-d-2eDdEe, in the chemical formula, x is greater than or equal to 0.67 and less than or equal to 0.85, a is greater than 0 and less than or equal to 0.05, b is greater than 0 and less than or equal to 0.10, c is greater than or equal to 0.03 and less than or equal to 0.10, d is greater than or equal to 0 and less than or equal to 0.05, e is greater than or equal to 0 and less than or equal to 0.05, and d + e is greater than 0 and less than or equal to 0.05; d is F-; e is S < 2->. Different functions of the elements are considered, sodium / vacancy orderliness in the charging and discharging process is effectively inhibited through the synergistic effect of the multiple elements, the sodium interlayer spacing is increased, the diffusion rate of sodium ions in the charging and discharging process is improved, and then the positive electrode material with the excellent rate capability is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion battery positive electrode materials, and in particular to a high-rate P2 type sodium ion battery layered positive electrode material and a preparation method thereof. Background Art

[0002] Lithium-ion batteries have been widely used in portable energy storage devices due to their advantages such as high safety, long service life and high energy density. However, the uneven distribution of lithium resources and their increasingly high prices have hindered the further application of lithium batteries, especially in large-scale energy storage. Sodium-ion batteries have the same working principle as lithium-ion batteries and have become one of the most promising candidate devices for large-scale energy storage applications and low-speed electric vehicles due to their low cost and abundant sodium resource reserves. As a key component of sodium-ion batteries, the positive electrode material has a significant impact on the electrochemical performance of sodium-ion batteries.

[0003] Layered metal oxides have the advantages of high specific capacity and working voltage, easy preparation, environmental friendliness, non-toxicity, and low cost, and have attracted extensive attention from researchers. Layered transition metal oxides are cathode materials for sodium ion batteries and can be divided into P2 type and O3 type according to the stacking order of oxygen atoms. + The triangular prism position and octahedral position occupying the sodium layer (NaO2) distinguish the P-type and O-type. Compared with the O3 phase structure, the P2 phase structure has higher ionic conductivity and lower diffusion barrier. Therefore, the P2-type layered oxide is a highly promising cathode material for sodium-ion batteries.

[0004] However, the commercial application of P2-type layered oxides is still restricted by the following two aspects. On the one hand, due to the Na + The radius is large, and during the charge and discharge process, due to Na + The deintercalation of Na + The diffusion kinetics deteriorates, and on the other hand, its unique occupancy mode and strong Na + -Na + Due to electrostatic interaction, the material will show an obvious orderly arrangement of sodium / vacancies in the sodium layer, which reduces its diffusion rate. Therefore, inhibiting the orderly arrangement of sodium / vacancies in the sodium layer and improving the cycle and rate performance of the material are crucial to promoting the industrialization of sodium-ion batteries.

[0005] Surface coating, structural design and element doping are common methods to improve the cycle performance of positive electrode materials. For example, patent document CN114388794A discloses an aluminum-doped zinc oxide-coated sodium nickel manganate positive electrode material. The highly conductive aluminum-doped zinc oxide coated on the sodium surface can reduce the contact between the positive electrode material and the electrolyte, inhibit the occurrence of side reactions, improve the cycle performance of the material, and improve the poor conductivity of the material itself, thereby enhancing the rate performance. Liu et al. regulated the Nae / Naf ratio by increasing the amount of sodium. The synthesized Na 0.696 Ni 0.329 Mn 0.671 O2 can still have 54.33mAh g at 50C -1 The discharge capacity of Mn was 2.347 W·m-1·K-1 and 2.504 W·m-1·K-1. However, the surface coating and structural design strategies have not completely solved the problem of sodium vacancy ordering during the charge and discharge process. Wang et al. chose to use Mn 4+ Ti with similar ionic radius but different Fermi levels 4+ To suppress the orderly arrangement of sodium vacancies, Ti 4+ After substitution, the electrons in the transition metal layer are localized, and the prepared P2-Na 2 / 3Ni 1 / 3 Mn 1 / 3 Ti 1 / 3 O2 exhibits a solid solution slope curve and shows excellent rate performance, with an initial capacity retention rate of 77.5% at a high rate of 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 O2 positive electrode material, which is composed of multi-layer directional stacked nanosheets, in which the nickel position is partially replaced by copper and magnesium. On the one hand, Na + The quasi-solid solution reaction of extraction / embedding is transformed into an absolute solid solution reaction; on the other hand, the multilayer oriented nanosheet structure can effectively promote the Na + The transfer kinetics of the electrode showed a capacity retention rate of 73% at 30C (Adv. Energy Mater. 2019, 1803978). However, the capacities of the above materials are all below 90 mAh / g, and the low capacity cannot meet the commercial needs of the battery.

[0006] Although the above methods have achieved certain results in improving the rate, the current research technology still has problems such as low capacity, reversible structural phase difference, failure to suppress sodium vacancy order, and complex preparation process, which hinders large-scale application. Summary of the invention

[0007] The purpose of the present invention is to provide a high-rate sodium ion battery layered positive electrode material and a preparation method thereof. Taking into account the different functions of elements, the synergistic effect of multiple elements is used to effectively suppress the sodium / vacancy order during the charge and discharge process, increase the sodium interlayer spacing, improve the diffusion rate of sodium ions during the charge and discharge process, and solve the problem of structural instability and poor rate performance of the P2-type layered oxide positive electrode of the sodium ion battery during the charge and discharge cycle.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions:

[0009] A high-rate P2-type sodium-ion battery layered cathode material with a chemical formula of 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<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; A metal ion is selected from K + , Rb + , C S + , Sr 2+ , Ba 2+ At least one of the metal ions B is selected from low-valent Li + Mg 2+ , Cu 2+ 、Zn 2+ , Fe 3+ 、Al 3+ One or more combinations of, C metal ions are selected from high-valent Ti 4+ 、Ce 4+ Sn 4+ 、Zr 4+ , Sb 5+ 、Bi 5+ , Nb 5+ 、 5+ 、Mo 6+ , W 6+ One of the following; D is F - ; E is S2- .

[0010] Preferably, the A metal ion is selected from Sr 2+ , Ba 2 At least one of the metal ions B is selected from low-valent Mg 2+ 、Zn 2+ At least one of the following, the C metal ion is selected from high-valent 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 A metal ion is Srr 2+ , B metal ion is selected from Mg 2+ 、Zn 2+ At least one of the C metal ions is Ti 4+ .

[0012] In a preferred embodiment of the present invention, the high-rate P2-type sodium ion battery layered positive electrode material has a chemical formula of 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] The present invention also provides a solid phase method for preparing the high-rate P2-type sodium ion battery layered positive electrode material, comprising the following steps:

[0014] (1) weighing a sodium-containing compound, a nickel-containing compound, a manganese-containing compound, and a doping element-containing compound according to the molar ratio of each element of the high-rate P2-type sodium ion battery layered positive electrode material;

[0015] (2) Each compound was placed in an agate ball mill jar, ethanol was used as a dispersant, and the mixture was mechanically mixed using a ball mill;

[0016] (3) sending the mixed slurry into a muffle furnace and pre-calcining it in an air atmosphere;

[0017] (4) The pre-sintered sample is fully ground and pressed into a disc using a tablet press;

[0018] (5) The pressed discs are placed in a muffle furnace for secondary calcination and then fully ground after cooling in the furnace.

[0019] Furthermore, 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, 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; the doping element-containing compound is selected from one or more of oxides, carbonate compounds, nitric acid compounds, acetic acid compounds, hydroxides, and halides of the doping element. If F and / or S exist in the layered positive electrode material of the high-rate P2 sodium ion battery, a certain proportion of sodium fluoride and / or sodium sulfide needs to be added.

[0020] Furthermore, in step (2), the ball mill speed is 300-800 rpm, and the speed time is 4-8 hours; in step (3), the first stage is programmed to heat up to 400-550° C. and then calcined for 4-6 hours; in step (4), the tablet press pressure is 15-20 MPa, and the tablet diameter is 10-15 mm; in step (5), the second stage is programmed to heat up to 850-1000° C. and then calcined for 10-15 hours.

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

[0022] (1) dissolving a water-soluble sodium-containing compound, a water-soluble nickel-containing compound, a water-soluble manganese-containing compound, and a water-soluble compound containing a doped metal element in deionized water according to the molar ratio of each element of the high-rate P2-type sodium ion battery layered positive electrode material, and then adding a chelating agent;

[0023] (2) stirring the solution obtained in step (1) at 60 to 90° C. for 4 to 8 hours to form a gel;

[0024] (3) placing the gel in an oven at 60 to 120° C. for 24 to 36 hours to obtain an intermediate product;

[0025] (4) The intermediate product is fully ground, calcined in stages in a muffle furnace, and cooled to obtain the positive electrode.

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

[0027] Preferably, the chelating agent is a compound 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 found that the compounded chelating agent can significantly improve the cycle stability of the obtained positive electrode material.

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

[0029] The present invention also provides the use of the high-rate P2-type sodium ion battery layered positive electrode material in the preparation of a sodium ion battery positive electrode material.

[0030] Preferably, the high-rate P2-type sodium-ion battery layered positive electrode material, conductive additive and binder are mixed in a mass ratio of 6-8:1-2:1-2 to form a slurry, which is evenly coated on an aluminum foil and dried to obtain a working electrode, which is then matched with metallic sodium and assembled into 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] The present invention provides a high-rate P2-type sodium-ion battery layered positive electrode material and a preparation method thereof. The target layered positive electrode material is synthesized by a solid phase method or a sol-gel method. The preparation method is simple and efficient. At the same time, the raw materials used are non-toxic, harmless, cheap and easy to obtain. Taking into account the different functions of the elements, the synergistic effect of multiple elements is used to effectively inhibit the sodium / vacancy order during the charge and discharge process, increase the interlayer spacing of the sodium layer, and improve the diffusion rate of the sodium ion charge and discharge process, thereby obtaining a positive electrode material with excellent rate performance. The material exhibits excellent electrochemical performance in the charge and discharge reaction process in the test range of 2.5V to 4.2V. Under the 0.1C rate test, the discharge reversible capacity is high and can reach 102mAh g -1 The above results show that the capacity retention rate is more than 90% after 300 cycles at 1C rate. In particular, the P2-type sodium ion battery layered positive electrode material obtained by the present invention has excellent rate performance through low-valent metal doping, high-valent metal doping, and F / S doping. Under the high rate test of 10C, the discharge capacity of the layered positive electrode material can reach 85mAh g -1 The above has practical electrochemical application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 is the 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 of .

[0035] Figure 2 is the 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 of .

[0036] Figure 3 is the 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 and discharge curve diagram.

[0037] Figure 4 The Na obtained in Comparative Example 1 0.78 Ni 0.33 Mn 0.67 The charge and discharge curve of O2.

[0038] Figure 5 is the 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 is the 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 obtained magnification diagram. DETAILED DESCRIPTION

[0040] The present invention will be further described below in conjunction with specific embodiments.

[0041] Example 1

[0042] Layered cathode materials for sodium ion batteries 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] Weigh 0.39mol sodium carbonate, 0.03mol strontium carbonate, 0.06mol zinc oxide, 0.27mol nickel oxide, 0.30mol manganese trioxide, 0.07mol titanium dioxide, and 0.05mol sodium fluoride powder into an agate ball mill jar, use ethanol as a dispersant, and mechanically mix them with a ball mill, where the ball milling speed is 500rpm and the ball milling time is 6 hours. The ball-milled sample is placed in a 60°C oven for drying to obtain a powder sample. The mixed powder is placed in a muffle furnace, calcined at 550°C for 6 hours, cooled naturally to room temperature and fully ground. The mixed powder sample is pressed into a disc with a diameter of 12mm at 16MPa using a tablet press, calcined at 900°C for 15 hours, and cooled to 200°C with the furnace to obtain a sodium ion battery positive electrode material.

[0044] Figure 1 The Na prepared in Example 1 of the present 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 into the hexagonal system, the space group is P63 / mmc, the diffraction peak is sharp, and there are no other obvious impurity peaks;

[0045] Figure 2 The Na prepared in Example 1 of the present 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 SEM image of the layered positive electrode material for sodium ion batteries shows that its morphology is plate-like particles with a particle size between 2 and 5 microns.

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

[0047] The sodium ion battery layered positive electrode material was prepared according to the conditions and methods basically the same as those in Example 1, specifically, the feed ratio of each element was adjusted according to the chemical formula of the positive electrode material in each example and comparative example.

[0048] Taking Example 12 as an example, the layered positive electrode material Na of the sodium ion battery is 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 0.365 mol of sodium carbonate, 0.03 mol of strontium carbonate, 0.06 mol of zinc oxide, 0.27 mol of nickel oxide, 0.30 mol of manganese trioxide, 0.07 mol of titanium dioxide, 0.03 mol of sodium fluoride, and 0.01 mol of sodium sulfide. The remaining steps are the same as those in Example 1.

[0050] Taking Example 13 as an example, the layered positive electrode material Na of the sodium ion battery is prepared 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 0.37 mol of sodium carbonate, 0.03 mol of strontium carbonate, 0.03 mol of zinc oxide, 0.03 mol of magnesium oxide, 0.27 mol of nickel oxide, 0.30 mol of manganese trioxide, 0.07 mol of titanium dioxide, 0.02 mol of sodium fluoride, and 0.01 mol of sodium sulfide. The remaining steps are the same as those in Example 1.

[0052] Taking Example 14 as an example, the layered positive electrode material Na of the sodium ion battery is 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 0.365 mol of sodium carbonate, 0.03 mol of strontium carbonate, 0.03 mol of zinc oxide, 0.03 mol of magnesium oxide, 0.27 mol of nickel oxide, 0.30 mol of manganese trioxide, 0.07 mol of titanium dioxide, 0.03 mol of sodium fluoride, and 0.01 mol of sodium sulfide. The remaining steps are the same as those in Example 1.

[0054] Taking Example 15 as an example, the layered positive electrode material Na of the sodium ion battery is prepared 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] Other conditions and operations were the same as in Example 12, except that the amount of sodium carbonate was changed to 0.4 mol.

[0056] Taking Example 16 as an example, the layered positive electrode material Na of the sodium ion battery is prepared 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 0.365 mol of sodium carbonate, 0.03 mol of strontium carbonate, 0.03 mol of zinc oxide, 0.03 mol of magnesium oxide, 0.27 mol of nickel oxide, 0.31 mol of manganese trioxide, 0.05 mol of titanium dioxide, 0.02 mol of sodium fluoride, and 0.01 mol of sodium sulfide. The remaining steps are the same as those in Example 1.

[0058] Embodiment 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, and a citric acid aqueous solution was added dropwise. The amount of citric acid was three times the molar amount of metal ions in the precursor. After adding citric acid, stirring was continued for 40 minutes;

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

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

[0063] (4) The above product was fully ground and calcined in a muffle furnace in stages. In the first stage, the temperature was raised to 450°C and then calcined for 6 hours. In the second stage, the temperature was raised to 900°C and then calcined for 12 hours, and then the temperature was lowered to 200°C. The obtained positive electrode was immediately transferred to an argon-protected glove box for later use.

[0064] Embodiment 25

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

[0066] Embodiment 26

[0067] The other conditions are the same as those 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] Layered cathode materials for sodium ion batteries 0.78 Ni0.33 Mn 0.67 O2 preparation steps.

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

[0071] Comparative Example 2

[0072] Layered cathode materials for sodium ion batteries 0.78 Sr 0.03 Ni 0.33 Mn 0.67 O2 preparation steps.

[0073] Weigh 0.335 mol of sodium carbonate, 0.03 mol of strontium carbonate, 0.33 mol of nickel oxide, and 0.335 mol of manganese trioxide. The remaining steps are the same as those in Example 1.

[0074] Comparative Example 3

[0075] Layered cathode materials for sodium ion batteries 0.78 Zn 0.06 Ni 0.27 Mn 0.67 O2 preparation steps.

[0076] Weigh 0.39 mol of sodium carbonate, 0.06 mol of zinc oxide, 0.27 mol of nickel oxide, and 0.335 mol of manganese trioxide. The remaining steps are the same as those in Example 1.

[0077] Comparative Example 4

[0078] Layered cathode materials for sodium ion batteries 0.78 Ni 0.33 Mn 0.67 O 1.95 F 0.05 Preparation steps.

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

[0080] Comparative Example 5

[0081] Layered cathode materials for sodium ion batteries 0.78 Ni 0.33 Mn 0.60 Ti 0.07 O2 preparation steps.

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

[0083] Application Examples

[0084] Sodium ion battery assembly: The positive electrode materials obtained in the sodium ion battery positive electrode material preparation example and the sodium ion battery positive electrode material preparation comparative example are used to prepare a sodium ion battery according to the following steps, as follows:

[0085] (1) The positive electrode materials prepared in the above embodiments and comparative examples were 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) was added. After pulping, coating, drying and other process steps, an electrode sheet with a diameter of 10 mm was obtained.

[0086] (2) The obtained positive electrode and the metallic sodium negative electrode are assembled into a sodium ion battery. The electrolyte contains NaClO4 with a concentration of 1 M. The solvent is a mixed solvent of propylene carbonate (PC) and fluoroethylene carbonate (FEC) with a volume ratio of 95:5. The separator adopts a porous glass fiber separator (Whatman, GF / D). The batteries are assembled into CR2025 button cells in an argon-filled glove box and subjected to electrochemical testing.

[0087] Electrochemical performance test:

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

[0089]

[0090]

[0091] It can be seen from the table that, compared with the comparative example, the sodium ion battery positive electrode material of the embodiment has better electrochemical performance. Figure 3 , 4 It can be seen that after the introduction of various doping elements, the sodium vacancy ordering and high-voltage phase transition during the charge and discharge process are significantly suppressed, thus showing excellent cycle performance and rate performance.

[0092] In particular, from Examples 12 to 16, it can be seen that in addition to doping with metal elements A, B, and C, doping with F and S simultaneously can lead to even better electrochemical performance of the resulting positive electrode material.

[0093] The positive electrode materials prepared from Example 12 and Examples 24-26 all have the chemical formula of 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 is a solid phase method, and Examples 24-26 are sol-gel methods. It can be seen that the electrochemical performance of the positive electrode materials obtained by the solid phase method or the sol-gel method is relatively excellent; the sol-gel method uses a single citric acid or hydroxyethylidene diphosphonic acid, and the electrochemical performance is not as good as the positive electrode material obtained by the solid phase method in Example 12; but Example 26 uses a mixed acid of citric acid or hydroxyethylidene diphosphonic acid as a chelating agent, and the cycle stability is the best.

[0094] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method 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 in the scope of protection of the present invention.

Claims

1. A high-rate P2-type sodium ion battery layered positive electrode 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 , wherein 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; A metal ion is selected from K + , Rb + , C S + , Sr 2+ , Ba 2+ At least one of the metal ions B is selected from low-valent Li + Mg 2+ , Cu 2+ 、Zn 2+ , Fe 3+ 、Al 3+ One or more combinations of, C metal ions are selected from high-valent Ti 4+ 、Ce 4+ Sn 4+ 、Zr 4+ , Sb 5+ 、Bi 5+ , Nb 5+ 、 5+ 、Mo 6+ , W 6+ One of the following; D is F - ; E is S 2- .

2. The high-rate P2-type sodium ion battery layered positive electrode material according to claim 1, characterized in that: A metal ion is selected from Sr 2+ , Ba 2 At least one of the metal ions B is selected from low-valent Mg 2+ 、Zn 2+ At least one of the following, the C metal ion is selected from high-valent 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.

3. The high-rate P2-type sodium ion battery layered positive electrode material according to claim 1, characterized in that: A metal ion is Srr 2+ , B metal ion is selected from Mg 2+ 、Zn 2+ At least one of the C metal ions is Ti 4+ .

4. The high-rate P2-type sodium ion battery layered positive electrode 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 、Na 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 、 or Na 0.78 Ba 0.02 Sr 0.01 Zn 0.06 Ni 0.27 Mn 0.60 Ti 0.07 The 1.95 F 0.05 。 5. The method for preparing the high-rate P2-type sodium ion battery layered positive electrode material according to any one of claims 1 to 4, characterized in that: It is a solid phase method, comprising the following steps: (1) weighing a sodium-containing compound, a nickel-containing compound, a manganese-containing compound, and a doping element-containing compound according to the molar ratio of each element of the high-rate P2-type sodium ion battery layered positive electrode material; (2) Each compound was placed in an agate ball mill jar, ethanol was used as a dispersant, and the mixture was mechanically mixed using a ball mill; (3) sending the mixed slurry into a muffle furnace and pre-calcining it in an air atmosphere; (4) The pre-sintered sample is fully ground and pressed into a disc using a tablet press; (5) The pressed discs are placed in a muffle furnace for secondary calcination and then fully ground after cooling in the furnace.

6. The preparation method according to claim 5, characterized in that: In the 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, 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; the doping element-containing compound is selected from one or more of oxides, carbonate compounds, nitric acid compounds, acetic acid compounds, hydroxides, and halides of the doping element.

7. The preparation method according to claim 5, characterized in that: In the step (2), the ball mill speed is 300-800 rpm, and the speed time is 4-8 hours; in the step (3), the first stage is programmed to heat up to 400-550° C. and then calcined for 4-6 hours; in the step (4), the tablet press pressure is 15-20 MPa, and the tablet diameter is 10-15 mm; in the step (5), the second stage is programmed to heat up to 850-1000° C. and then calcined for 10-15 hours.

8. The method for preparing the high-rate P2-type sodium ion battery layered positive electrode material according to any one of claims 1 to 4, characterized in that: It is a sol-gel method, comprising the following steps: (1) dissolving a water-soluble sodium-containing compound, a water-soluble nickel-containing compound, a water-soluble manganese-containing compound, and a water-soluble compound containing a doped metal element in deionized water according to the molar ratio of each element of the high-rate P2-type sodium ion battery layered positive electrode material, and then adding a chelating agent; (2) stirring the solution obtained in step (1) at 60 to 90° C. for 4 to 8 hours to form a gel; (3) placing the gel in an oven at 60 to 120° C. for 24 to 36 hours to obtain an intermediate product; (4) grinding the intermediate product fully, calcining it in stages in a muffle furnace, and obtaining the positive electrode after cooling; The chelating agent in step (1) is at least one of citric acid and malic acid, and the amount of the chelating agent added is 2-4 times the molar mass of the metal ion. After adding the chelating agent, stir at 400-800 rom for 30-60 minutes.

9. The preparation method according to claim 8, characterized in that: The dropping rate in step (1) is 2 to 5 mL / min; the calcination in step (4) is divided into two stages, the first stage is programmed to heat up to 350 to 550° C. and then calcined for 4 to 8 hours; the second stage is programmed to heat up to 850 to 950° C. and then calcined for 10 to 12 hours, and then programmed to cool down to 200 to 250° C., and the obtained positive electrode is immediately transferred to an argon-protected glove box for later use.

10. Use of the high-rate P2-type sodium ion battery layered positive electrode material according to any one of claims 1 to 4 in the preparation of a sodium ion battery positive electrode material.

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