A high-aspect-ratio hexagonal prism type layered oxide positive electrode material and a preparation method thereof

Abstract

The application relates to a high-aspect-ratio hexagonal prism type layered oxide positive electrode material and a preparation method thereof, and belongs to the technical field of lithium ion batteries and sodium ion batteries. A precursor is obtained by combining dry ball milling with wet ball milling of raw materials and a surfactant, the precursor is sintered in an argon atmosphere combined with an air atmosphere to obtain Na x Mn y M 1‑y O2 positive electrode material, and Li x Mn y M 1‑y O2 positive electrode material is obtained by sintering a mixed lithium source. The positive electrode material has a high-aspect-ratio hexagonal prism morphology, and the proportion of active crystal faces (010) is high. The scheme of the application is to improve ion diffusion kinetics by using high-exposure active crystal faces, solve the problem of poor two-dimensional channel diffusion rate of layered oxide positive electrodes of lithium ion batteries and sodium ion batteries, and further enhance the structural stability, so that the positive electrode material has good rate performance and cycle stability.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium ion batteries and sodium ion batteries, and particularly relates to a high-aspect-ratio hexagonal prism type layered oxide positive electrode material and a preparation method thereof. BACKGROUND

[0002] Layered transition metal oxides are a kind of early studied intercalation compounds due to their periodic layered structure and two-dimensional ion transmission channels, and have been widely studied in lithium ion batteries and sodium ion batteries, and are a kind of positive electrode material with great development potential. However, due to complex phase transition and slow Li / Na diffusion, poor cycle stability and limited rate capability, etc., further practical application is hindered.

[0003] Ion transmission kinetics in the electrode material plays a key role in the battery performance, which depends largely on the host structure and ion diffusion tunnel. A stable host structure can avoid the collapse of the lattice and diffusion channel, which is a prerequisite for reversible intercalation and deintercalation of ions, and constructing a tunnel more conducive to diffusion can accelerate the rapid migration of ions. Therefore, the key to solving the problem of slow ion kinetics lies in constructing a stable host structure with more migration tunnels.

[0004] For layered oxide positive electrodes, the electrochemically inert crystal surface is usually exposed during the preparation process, which causes the ion deintercalation to be blocked during the charging and discharging process, and exposing the (010) active crystal surface of the primary particles provides an additional ion transmission channel, which is an effective method to enhance the diffusion kinetics. SUMMARY

[0005] The purpose of the present application is to solve the above-mentioned problems existing in the background art, and to provide a high-aspect-ratio hexagonal prism type layered oxide sodium / lithium ion battery positive electrode material and a preparation method thereof. The present application utilizes the high-exposed active crystal surface to improve the ion diffusion kinetics, solves the problem of poor two-dimensional channel diffusion rate of the layered oxide positive electrode of the lithium ion battery and the sodium ion battery, and further enhances the structural stability, so that the positive electrode material obtains good rate performance and cycle stability.

[0006] To achieve the above-mentioned purposes, the technical solutions adopted by the present application are as follows:

[0007] A high-aspect-ratio hexagonal prism type layered oxide positive electrode material, the chemical formula of the high-aspect-ratio hexagonal prism type layered oxide positive electrode material is A x Mn y M 1-yO2, wherein A is Li or Na, M is one or more of Li, B, Mg, Al, Si, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Zr, Nb, La and Sn, 0.6≤x≤1, 0.5≤y≤1; the particle diameter of the positive electrode material is 0.2-0.5 μm in width and 2.0-4.0 μm in length; and the aspect ratio of the positive electrode material is 5-10.

[0008] Further, the radial exposed surface of the positive electrode material is an (010) active crystal surface.

[0009] A preparation method of the high-aspect-ratio hexagonal prism layered oxide positive electrode material is provided.

[0010] (1) A Na source, a Mn source and a M source are mixed according to stoichiometric ratios, and a certain amount of a surfactant is added, wet ball milling is performed by first adding a ball milling medium, the ball milling medium is allowed to evaporate naturally after ball milling, and dry ball milling is continued to obtain a mixture precursor;

[0011] (2) According to the different selection of A elements, the following two schemes are provided:

[0012] Scheme one: the mixture precursor obtained in step (1) is sintered in an argon atmosphere at 400-500 ℃, and then sintered in an oxygen atmosphere at 700-1000 ℃, to obtain a Na x Mn y M 1-y O2 positive electrode material;

[0013] Scheme two: based on scheme one, further comprising: the Na x Mn y M 1-y O2 positive electrode material is mixed with LiNO3 / LiCl (88:12 mass ratio) at a mass ratio of 1:2, and a Li x Mn y M 1-y O2 positive electrode material is obtained after sintering at 250-350 ℃.

[0014] The high aspect ratio of the prepared material is derived from the combined effects of element selection, surfactant, inert atmosphere pre-sintering and subsequent sintering process.

[0015] Further, in step (1), the Na and the precursors of the remaining elements are selected from at least one of oxides, hydroxides, carbonates, nitrates or oxalates thereof.

[0016] Further, in step (1), the surface active agent is at least one of polyvinylpyrrolidone, sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium dodecyl phosphate, sodium butylnaphthalene sulfonate, cetyltrimethylammonium bromide, polyvinyl alcohol, lauric acid, polyethylene wax, octylphenol polyoxyethylene ether and cocamidopropyl hydroxyl sultaine; the molecular weight of the polyvinylpyrrolidone is 8000-40000, the molecular weight of the polyvinyl alcohol is 30000-70000, and the molecular weight of the polyethylene wax is 1500-5000; and the addition amount of the surface active agent is 5-30% of the mass of other raw materials.

[0017] Further, in step (1), the ball milling medium is one of ethanol, acetone, n-hexane and cyclohexane.

[0018] Further, in step (1), the wet ball milling time is 2-8h, and the ball milling speed is 500-1000rpm; the dry ball milling time is 1-4h, and the ball milling speed is 500-1000rpm.

[0019] Further, in scheme one, the argon atmosphere sintering time of the first step is 3-6h, and the oxygen atmosphere sintering time of the second step is 10-20h.

[0020] Further, in scheme two, the material sintering time is 2-6h, and the sintering atmosphere is oxygen or air.

[0021] The lithium ion battery and the sodium ion battery comprise the above positive electrode material.

[0022] The beneficial results of the present application relative to the prior art are:

[0023] (1) The present application adopts a simple mixing and calcination process, and the preparation process is simple.

[0024] (2) The present application realizes the synthesis of a high aspect ratio layered oxide, has rich active crystal face exposure, is beneficial to ion intercalation and deintercalation, and greatly improves the rate performance of the two-dimensional layered oxide positive electrode material without introducing additional elements.

[0025] (3) The method adopted by the present application is directly applied to the field of sodium ion batteries, and can be applied to the field of lithium ion batteries through simple molten salt conversion.

[0026] (4) The positive electrode material of the present application shows a hexagonal prism morphology, the morphology is uniform, and as a positive electrode material has high reversible capacity and excellent electrochemical performance. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a schematic diagram of a high aspect ratio hexagonal prism type layered oxide positive electrode material;

[0028] Figure 2 SEM image of the positive electrode material prepared for Example 1;

[0029] Figure 3 SEM image of the positive electrode material prepared for Example 6;

[0030] Figure 4 Rate performance chart of the positive electrode material prepared for Example 1, Example 2, and Comparative Example 1. DETAILED DESCRIPTION

[0031] The technical solutions of the present application are further described below in conjunction with the drawings and examples, but are not limited thereto. Any modification or equivalent replacement to the technical solutions of the present application without departing from the spirit and scope of the technical solutions shall be covered in the protection scope of the present application.

[0032] Example 1

[0033] In this example, a high aspect ratio hexagonal prism type layered oxide positive electrode was prepared according to the stoichiometric ratio of Na 0.72 Li 0.24 Mn 0.76 O2. The specific steps included: weighing Na2CO3(excess 5%), LiOH(excess 3%) and MnO2according to the stoichiometric ratio in a ball mill jar, adding 30% mass fraction of polyvinylpyrrolidone(molecular weight 40000), adding zirconium dioxide ball milling beads according to the ball material ratio of 10:1, adding a certain amount of n-hexane to immerse the ball milling beads and the material, and ball milling at a speed of 500 rpm for 4 h. After opening the lid to completely volatilize the n-hexane, continue to ball mill at a speed of 500 rpm for 2 h to obtain the ball milling precursor. Then sinter in a tube furnace at 430℃ under argon atmosphere for 5 h and at 700℃ under air atmosphere for 20 h. The Na 0.72 Li 0.24 Mn 0.76 O2was subjected to electron microscopy scanning, and the SEM image is shown in Figure 2 It can be seen that the material exhibits a clear hexagonal prism morphology, the particle size is relatively uniform, the transmission channel of the sodium ion battery is expanded, and the sodium ion transmission capacity is improved.

[0034] Example 2

[0035] In this example, a high aspect ratio hexagonal prism type layered oxide positive electrode was prepared according to the stoichiometric ratio of Na 0.8MnO2stoichiometrically prepared high aspect ratio hexagonal prism layered oxide cathode, the specific steps include: according to the stoichiometric ratio of Na2CO3(excess 5%) and MnO2in the ball mill tank, 10% mass fraction of butyl naphthalene sulfonate sodium is added, zirconium dioxide ball milling beads are added according to the ball material ratio of 10:1, a certain amount of n-hexane is added to immerse the ball milling beads and the material, and ball milling is carried out at 500 rpm for 4 h. After opening the cover to let the n-hexane completely evaporate, ball milling is continued at 500 rpm for 2 h to obtain the ball-milled precursor. Then, sintering is carried out in a tube furnace at 500 DEG C in an argon atmosphere for 5 h, and sintering is carried out at 700 DEG C in an air atmosphere for 12 h.

[0036] Example 3

[0037] In this example, Na 0.72 Li 0.24 Mn 0.76 O2stoichiometrically prepared high aspect ratio hexagonal prism layered oxide cathode, the specific steps include: according to the stoichiometric ratio of Na2CO3(excess 5%), LiOH(excess 3%) and MnO2in the ball mill tank, 20% mass fraction of lauric acid is added, zirconium dioxide ball milling beads are added according to the ball material ratio of 10:1, a certain amount of ethanol is added to immerse the ball milling beads and the material, and ball milling is carried out at 700 rpm for 6 h. After opening the cover to let the ethanol completely evaporate, ball milling is continued at 500 rpm for 2 h to obtain the ball-milled precursor. Then, sintering is carried out in a tube furnace at 500 DEG C in an argon atmosphere for 5 h, and sintering is carried out at 700 DEG C in an air atmosphere for 15 h.

[0038] Example 4

[0039] In this example, Na 0.67 Ni 0.33 Mn 0.67 O2stoichiometrically prepared high aspect ratio hexagonal prism layered oxide cathode, the specific steps include: according to the stoichiometric ratio of Na2CO3(excess 5%), NiO and MnO2in the ball mill tank, 10% mass fraction of polyvinylpyrrolidone(molecular weight 40000) is added, zirconium dioxide ball milling beads are added according to the ball material ratio of 10:1, a certain amount of n-hexane is added to immerse the ball milling beads and the material, and ball milling is carried out at 800 rpm for 4 h. After opening the cover to let the n-hexane completely evaporate, ball milling is continued at 500 rpm for 2 h to obtain the ball-milled precursor. Then, sintering is carried out in a tube furnace at 450 DEG C in an argon atmosphere for 5 h, and sintering is carried out at 900 DEG C in an air atmosphere for 20 h.

[0040] Example 5

[0041] In this example, Na 0.67 Fe 0.5 Mn 0.5O2stoichiometrically. The specific steps include: taking Na2CO3 (5% excess), Fe2O3 and MnO2 according to the stoichiometric ratio in a ball mill jar, adding 10% mass fraction of sodium dodecyl benzene sulfonate, adding zirconium dioxide ball milling beads according to the ball material ratio of 10:1, adding a certain amount of ethanol to immerse the ball milling beads and the materials, ball milling at 800 rpm for 4 h. After opening the cover to completely evaporate the ethanol, continue to ball mill at 500 rpm for 2 h to obtain the ball-milled precursor. Then sinter in a tube furnace at 500°C under argon atmosphere for 5 h, and at 900°C under air atmosphere for 20 h.

[0042] Example 6

[0043] In this example, the Na 5 / 6 Li 1 / 4 Co 0.244 Mn 0.506 O2stoichiometrically. The specific steps include: taking Na2CO3 (5% excess), Fe2O3 and MnO2 according to the stoichiometric ratio in a ball mill jar, adding 10% mass fraction of sodium dodecyl benzene sulfonate, adding zirconium dioxide ball milling beads according to the ball material ratio of 10:1, adding a certain amount of ethanol to immerse the ball milling beads and the materials, ball milling at 800 rpm for 4 h. After opening the cover to completely evaporate the ethanol, continue to ball mill at 500 rpm for 2 h to obtain the ball-milled precursor. Then sinter in a tube furnace at 500°C under argon atmosphere for 5 h, and at 900°C under air atmosphere for 20 h. 5 / 4 Co 0.244 Mn 0.506 O2stoichiometrically. The specific steps include: taking Na2CO3 (5% excess), Fe2O3 and MnO2 according to the stoichiometric ratio in a ball mill jar, adding 10% mass fraction of sodium dodecyl benzene sulfonate, adding zirconium dioxide ball milling beads according to the ball material ratio of 10:1, adding a certain amount of ethanol to immerse the ball milling beads and the materials, ball milling at 800 rpm for 4 h. After opening the cover to completely evaporate the ethanol, continue to ball mill at 500 rpm for 2 h to obtain the ball-milled precursor. Then sinter in a tube furnace at 500°C under argon atmosphere for 5 h, and at 900°C under air atmosphere for 20 h. 5 / 4Co 0.244 Mn 0.506 O2stoichiometrically. The specific steps include: taking Na2CO3 (5% excess), Fe2O3 and MnO2 according to the stoichiometric ratio in a ball mill jar, adding 10% mass fraction of sodium dodecyl benzene sulfonate, adding zirconium dioxide ball milling beads according to the ball material ratio of 10:1, adding a certain amount of ethanol to immerse the ball milling beads and the materials, ball milling at 800 rpm for 4 h. After opening the cover to completely evaporate the ethanol, continue to ball mill at 500 rpm for 2 h to obtain the ball-milled precursor. Then sinter in a tube furnace at 500°C under argon atmosphere for 5 h, and at 900°C under air atmosphere for 20 h. Figure 3 As can be seen, the material after lithium conversion still exhibits a clear hexagonal prism morphology, and the particle size is relatively uniform, which has good application potential in lithium ion batteries.

[0044] Example 7

[0045] In this example, the Li 1.24 Mn 0.76 O2stoichiometrically. The specific steps include: taking Na2CO3 (5% excess), Fe2O3 and MnO2 according to the stoichiometric ratio in a ball mill jar, adding 10% mass fraction of sodium dodecyl benzene sulfonate, adding zirconium dioxide ball milling beads according to the ball material ratio of 10:1, adding a certain amount of ethanol to immerse the ball milling beads and the materials, ball milling at 800 rpm for 4 h. After opening the cover to completely evaporate the ethanol, continue to ball mill at 500 rpm for 2 h to obtain the ball-milled precursor. Then sinter in a tube furnace at 500°C under argon atmosphere for 5 h, and at 900°C under air atmosphere for 20 h.

[0046] Example 8

[0047] The material after sintering is sintered with LiNO3 / LiCl (88:12 w / w) at a mass ratio of 1:2 in an air atmosphere at 350℃ for 6h to obtain LiNi 0.33 Mn 0.67 O2.

[0048] Comparative Example 1

[0049] The layered oxide positive electrode is prepared according to the stoichiometric ratio of Na 0.72 Li 0.24 Mn 0.76 O2stoichiometric ratio, and the specific steps include: taking Na2CO3 (excess 5%), LiOH (excess 3%) and MnO2 according to the stoichiometric ratio in a ball mill jar, adding zirconium dioxide milling balls according to a ball-to-material ratio of 10:1, and ball milling at a speed of 500 rpm for 4h to obtain a precursor, and then sintering at 700℃ in an air atmosphere in a tube furnace for 15h.

[0050] Comparative Example 2

[0051] The layered oxide positive electrode is prepared according to the stoichiometric ratio of Li 5 / 4 Co 0.244 Mn 0.506 O2stoichiometric ratio, and the specific steps include: taking Li2CO3 (excess 5%), Co3O4 and MnO2 according to the stoichiometric ratio in a ball mill jar, adding zirconium dioxide milling balls according to a ball-to-material ratio of 10:1, and ball milling at a speed of 500 rpm for 4h to obtain a precursor, and then sintering at 700℃ in an air atmosphere in a tube furnace for 15h.

[0052] The positive electrode materials prepared in Example 1, Example 2 and Comparative Example 1 are subjected to rate performance tests, and the rate performance is shown in Table 1. Figure 4 The high aspect ratio material prepared by the present application has better rate performance than the material prepared by the traditional method.

[0053] The layered oxide materials prepared in the above various embodiments and comparative examples of the present application are tested.

[0054] Half-cell assembly: Take the positive electrode material in each example and comparative example as the active material, mix it with the conductive agent Super P and the binder polyvinylidene fluoride (PVDF) in a mass ratio of 7:2:1, take N-methyl pyrrolidone (NMP) as the solvent, place it in a weighing bottle and stir for 12 h to obtain a slurry. Use a coater to coat the slurry on a current collector aluminum foil, transfer it to a vacuum drying oven at 120°C and dry for 12 h, punch the sheet to prepare a pole piece with a diameter of 14 mm, accurately weigh the pole piece, take a lithium sheet / sodium sheet as the negative electrode, dissolve 1 mol / L of LiFP6 / NaClO4 in a propylene carbonate (PC): ethylene carbonate (EC) (volume ratio 1:1) solution as the electrolyte, use a glass fiber separator, and assemble a CR2032 button cell half-cell in an argon glove box.

[0055] Charge-discharge test: For lithium ion battery materials, the voltage range of the button cell charge-discharge is 2.0-4.8V, and for sodium ion battery materials, the voltage range of the button cell charge-discharge is 2.0-4.5V. Before the cycle test, a smaller current density of 20mA / g (0.1C) is used for three times of activation, and then the cycle is carried out at 1C rate in the same voltage range. All electrochemical performance tests are carried out at room temperature.

[0056] The electrochemical performance of the half-cell assembled with the materials of the examples and comparative examples is tested respectively, and the initial capacity at 0.1C and 10C rates and the capacity retention rate after 100 cycles at 1C rate are as follows.

[0057]

Claims

1. A method for preparing a high aspect ratio hexagonal prism-shaped layered oxide cathode material, characterized in that: The chemical formula of the high aspect ratio hexagonal prism-shaped layered oxide cathode material is A. x Mn y M 1-y O2, wherein A is Li or Na, M is one or more of Li, B, Mg, Al, Si, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Zr, Nb, La, and Sn, 0.6≤x≤1, 0.5≤y≤1; the radial width of the positive electrode material particles is 0.2~0.5 μm, and the length is 2.0~4.0 μm; the method is as follows: (1) Na source, Mn source and M source are mixed according to stoichiometric ratio, and a certain amount of surfactant is added. First, ball milling media are added for wet ball milling. After ball milling, the ball milling media are allowed to evaporate naturally, and dry ball milling is continued to obtain the mixture precursor. The amount of surfactant added is 5~30% of the mass of other raw materials. (2) Depending on the different elements selected by A, there are two specific schemes: Option 1: Sinter the mixture precursor obtained in step (1) in an argon atmosphere at 400~500℃, followed by sintering in an oxygen atmosphere at 700~1000℃ to obtain Na. x Mn y M 1-y O2 cathode material; the first step of argon atmosphere sintering time is 3~6 h, and the second step of oxygen atmosphere sintering time is 10~20 h; Option 2: In addition to Option 1, it also includes: Na x Mn y M 1-y O2 cathode material was mixed with LiNO3 / LiCl at a mass ratio of 1:2, and sintered at 250~350℃ to obtain Li x Mn y M 1-y O2 cathode material; the mass ratio of LiNO3 to LiCl is 88:

12.

2. The method for preparing the high aspect ratio hexagonal prism-shaped layered oxide cathode material according to claim 1, characterized in that: The radial exposed surface of the cathode material is the (010) active crystal plane.

3. The method for preparing the high aspect ratio hexagonal prism-shaped layered oxide cathode material according to claim 1, characterized in that: In step (1), the precursors of Na and the other elements are selected from at least one of their oxides, hydroxides, carbonates, nitrates or oxalates.

4. The method for preparing the high aspect ratio hexagonal prism-shaped layered oxide cathode material according to claim 1, characterized in that: In step (1), the surfactant is at least one of polyvinylpyrrolidone, sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, sodium dodecyl phosphate, sodium butylnaphthalenesulfonate, hexadecyltrimethylammonium bromide, polyvinyl alcohol, lauric acid, polyethylene wax, octylphenol polyoxyethylene ether, and cocamidopropyl hydroxysulfonate; the molecular weight of the polyvinylpyrrolidone is 8000~40000, the molecular weight of the polyvinyl alcohol is 30000~70000, and the molecular weight of the polyethylene wax is 1500~5000.

5. The method for preparing the high aspect ratio hexagonal prism-shaped layered oxide cathode material according to claim 1, characterized in that: In step (1), the ball milling medium is one of ethanol, acetone, n-hexane and cyclohexane.

6. The method for preparing the high aspect ratio hexagonal prism-shaped layered oxide cathode material according to claim 1, characterized in that: In step (1), the wet ball milling time is 2~8 h and the ball milling speed is 500~1000 rpm; the dry ball milling time is 1~4 h and the ball milling speed is 500~1000 rpm.

7. The method for preparing the high aspect ratio hexagonal prism-shaped layered oxide cathode material according to claim 1, characterized in that: In Option 2, the sintering time of the material is 2-6 hours, and the sintering atmosphere is oxygen or air.

8. A lithium-ion battery and a sodium-ion battery, comprising the positive electrode material as described in any one of claims 1 to 2.

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