P2 type solid electrolyte in-situ coated O3 type sodium ion battery oxide positive electrode material and preparation method thereof

Abstract

The invention discloses a P2-type solid electrolyte in-situ coated O3-type layered oxide positive electrode material and a preparation method and application thereof, the O3-type oxide is a layered metal oxide, and the chemical general formula of the O3-type oxide is NaxNiyMnzFe1-y-zO2 (0.85 lt; xlt; 1.1, 0.1 lt; yt; Yt; 0.9, 0.1 lt; zlt, zlt; 0.9), the surface of which is uniformly coated with a P2 type solid electrolyte layer. The preparation method comprises the following steps: uniformly mixing spherical NiyMnzFe1-y-z (OH) 2 precursor secondary particles with a sodium source, the coating layer metal source and tellurium dioxide through a wet chemical method, carrying out high-temperature calcination on the mixture in a proper atmosphere, and cooling to obtain the positive electrode material. The preparation method is simple, lattice coherence coating of primary particles of the material on the nanoscale is achieved, and the product is good in air stability and has excellent cycle performance and ultrafast sodium ion dynamic transmission performance.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sodium ion battery cathode materials, and particularly relates to a P2 type solid electrolyte Na2M2TeO6 coated O3 type oxide cathode material and a preparation method thereof. BACKGROUND

[0002] Sodium ion batteries are widely concerned in the field of large-scale energy storage due to rich sodium resource reserves and low cost. Among them, O3 type layered oxide cathode materials (general chemical formula Na x TMO2, TM is a transition metal) are considered as a candidate system with great application potential due to high theoretical specific capacity (≥180 mAh / g) and moderate working voltage window (3.0-3.8 V vs. Na + / Na). However, the O3 type material has significant defects in practical application: strong alkaline substances (such as Na2CO3, NaOH) are easily left on the surface during the synthesis process, leading to side reactions with the electrolyte and significantly increasing the interface impedance; at the same time, when the material is exposed to humid air, the interlayer sodium ions are easily reacted with H2O / CO2 to generate inactive compounds (such as NaHCO3), causing rapid decay of reversible capacity (experiments show that the capacity loss of uncoated materials is more than 15% in a humidity of 60% environment for 72 hours). In addition, during the repeated sodium removal process, the O3 type material is prone to irreversible phase transition, causing lattice distortion and internal micro-cracks in the particles, resulting in a sharp decline in cycle stability. The above problems seriously restrict the industrialization process.

[0003] To solve the defects of the O3 type material, researchers have proposed various modification strategies, but all have limitations. For example, surface coating with inert oxides such as Al2O3, TiO2 can partially isolate the material from the side reactions with the electrolyte, but such coating layer hinders the transmission of sodium ions, resulting in a decline in rate performance of more than 30%; the bulk doping strategy improves the structural stability by introducing Li + , Mg 2+ and other hetero ions, but the doping process is complex and easily introduces lattice defects, and the ionic conductivity of the material is only improved to the order of 10 -4 S / cm; while the composite NASICON type solid electrolyte (such as Na3Zr2Si2PO 12 ) can improve the interface compatibility, but due to the large difference in lattice constants (>5%) with the O3 matrix, the coating layer is prone to cracking and falling off due to stress mismatch. Therefore, developing a coating technology with high ionic conductivity, structural adaptability and process feasibility and the corresponding composite material is still a technical difficulty in this field. SUMMARY

[0004] Based on this, the present invention proposes a new interface engineering strategy: using P2-type Na2M2TeO6 (M = Zn, Mg, Ca, etc.) solid electrolyte to perform lattice coherent coating on O3-type oxide. This design is based on a deep analysis of the intrinsic properties of the material - the lattice parameters of P2-type Na2M2TeO6 With O3 matrix Highly matched, it can form an atomic-level dense interface through coherent epitaxial growth, fundamentally avoiding the lattice mismatch problem of traditional coating. At the same time, P2-type Na2M2TeO6 has both high sodium ion conductivity (10 -4 S / cm) and electronic insulation properties, which can both suppress surface side reactions and enable rapid sodium ion transport. Through solid-phase synthesis and wet mixed secondary calcination, this invention achieves precise control of the nanoscale (5-20nm) coating layer, at a cost of only 20% of atomic layer deposition (ALD) technology, providing a new paradigm for the large-scale preparation of high-performance sodium-ion battery cathode materials.

[0005] In order to achieve the purpose of this invention, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a method for preparing an O3-type layered oxide positive electrode material in situ coated with an in-situ P2-type metal sodium tellurite solid electrolyte, the preparation method comprising the following steps:

[0007] Spherical Ni was prepared by wet chemical method y Mn z Fe 1-y-z The (OH)2 precursor is uniformly mixed with the sodium source, the coating layer metal source and tellurium dioxide. After the solvent evaporates, the mixture is calcined at a high temperature in a suitable atmosphere, and the positive electrode material is obtained after the temperature is lowered.

[0008] Preferably, the spherical Ni y Mn z Fe 1-y-z The D50 of the (OH)2 precursor secondary particles is 1-10 μm, the particle size distribution is (D90-D10) / D50<0.80, and the tap density is 1.4-2.4 g / cm 3 , with a specific surface area of ​​5 to 60 m 2 / g.

[0009] Preferably, the sodium source is at least one of sodium carbonate, sodium hydroxide, sodium bicarbonate, sodium oxalate, sodium bioxalate, and sodium acetate.

[0010] Preferably, the metal source of the coating layer is a water-soluble or alcohol-soluble salt such as acetate or nitrate of each metal (one or two or more of Zn, Mg, Cu, Ca, Ga, Ni).

[0011] Preferably, the material uniform mixing method is to use spherical Ni y Mn z Fe 1-y-z A wet chemical impregnation method for realizing the uniform adhesion of the material source of the coating layer on the surface of the precursor by taking advantage of the different solubilities of different components in the dispersion system and the coincidence of the solid phase reaction temperature ranges of the matrix material and the coating layer, and fusing the coating process in the high-temperature solid phase sodiumization calcination process.

[0012] Preferably, the appropriate atmosphere is an air atmosphere, an oxygen atmosphere or a mixed gas of the two in any volume ratio.

[0013] Preferably, the high-temperature calcination temperature of the mixture is 600-1100℃, the heating rate is 1-20℃ / min, the holding time is 3-24h, and the cooling rate is 1-50℃ / min.

[0014] In a second aspect, the present application provides an O3-type layered oxide positive electrode material coated in situ by a P2-type metal sodium tellurite solid-state electrolyte, wherein the sodium battery positive electrode material is prepared by the preparation method of the first aspect.

[0015] Preferably, the O3-type oxide is a layered metal oxide, and the chemical general formula is Na x Ni y Mn z Fe 1-y-z O2, wherein 0.85

[0016] In a third aspect, the present application provides a sodium ion battery, wherein the sodium ion battery comprises the sodium battery positive electrode material of the second aspect.

[0017] Compared with the prior art, the present application has the following beneficial effects:

[0018] The present application takes a mature sodium battery precursor as the basis, utilizes the different solubilities of different components in the dispersion system, realizes the uniform adhesion of the material source of the coating layer on the surface of the precursor in the process of the wet chemical method, and utilizes the coincidence of the solid phase reaction temperature ranges of the matrix material and the coating layer to fuse the coating process in the high-temperature solid phase sodiumization calcination process. This in-situ coating method not only realizes the coating of the nanoscale fast ion conductor, but also avoids the contact of the O3-type positive electrode material with H2O and CO2 in the air, thereby improving the air stability. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 X-ray diffraction test results of the positive electrode materials obtained in Examples 1-4 and Comparative Examples

[0020] Figure 2High-resolution transmission electron microscopy results of the positive electrode materials obtained in Example 2 and the comparative example: (a) Example 2; (b) Comparative example

[0021] Figure 3 Comparison of the rate performance of the positive electrode materials obtained in Example 2 and the comparative example DETAILED DESCRIPTION

[0022] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the O3-type layered oxide positive electrode material in situ coated with the P2-type metal sodium tellurite solid electrolyte of the present invention will be further described in conjunction with specific embodiments and drawings of the specification. However, it should be understood that the scope of protection of the present invention is not limited to the following embodiments.

[0023] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or those recommended by the manufacturer. All reagents or instruments used, if the manufacturer is not specified, are commercially available conventional products.

[0024] Example 1

[0025] This embodiment provides a preparation method of an O3 type layered oxide positive electrode material in situ coated with a P2 type metal sodium tellurate solid electrolyte, the preparation method comprising the following steps: 0.1461 g of tellurium dioxide (calculated as tellurium dioxide, the target coating amount is 1%) is added to the cathode material by a wet chemical method. wt ) and 0.336g of metal source zinc acetate were dissolved in anhydrous ethanol, and 9.045g of spherical Ni with a particle size D50 of 5.35μm was added to the wet chemical dispersion system. y Mn z Fe 1-y-z The (OH)2 precursor and 5.66g of anhydrous sodium carbonate were mixed. The dispersion was heated and stirred using a magnetic stirrer. After the anhydrous ethanol evaporated, the mixed powder was calcined at 900°C for 12 hours in an air atmosphere at a heating rate of 5°C / min, and then cooled at a rate of 5°C / min to obtain the positive electrode material.

[0026] Example 2

[0027] This embodiment provides a method for preparing an O3-type layered oxide positive electrode material in situ coated with a P2-type metal sodium tellurite solid electrolyte. The preparation method comprises the following steps: 0.2922 g of tellurium dioxide (calculated as tellurium dioxide, the target coating layer coating amount is 2%) is added by a wet chemical method. wt ) and 0.672g of metal source zinc acetate were dissolved in anhydrous ethanol, and 9.045g of spherical Ni with a particle size D50 of 5.35μm was added to the wet chemical dispersion system. y Mn z Fe 1-y-zThe (OH)2 precursor and 5.755g of anhydrous sodium carbonate were mixed. The dispersion was heated and stirred using a magnetic stirrer. After the anhydrous ethanol evaporated, the mixed powder was calcined at 900°C for 12 hours in an air atmosphere at a heating rate of 5°C / min and then cooled at a rate of 5°C / min to obtain the positive electrode material.

[0028] Example 3

[0029] This embodiment provides a method for preparing an O3-type layered oxide positive electrode material in situ coated with a P2-type metal sodium tellurite solid electrolyte. The preparation method comprises the following steps: 0.5844 g of tellurium dioxide (calculated as tellurium dioxide, the target coating amount is 4%) is added by a wet chemical method. wt ) and 1.344 g of the coating metal source zinc acetate were dissolved in anhydrous ethanol, and 9.045 g of spherical Ni with a particle size D50 of 5.35 μm was added to the wet chemical dispersion system. y Mn z Fe 1-y-z The (OH)2 precursor and 5.945g of anhydrous sodium carbonate were mixed. The dispersion was heated and stirred using a magnetic stirrer. After the anhydrous ethanol evaporated, the mixed powder was calcined at 900°C for 12 hours in an air atmosphere at a heating rate of 5°C / min and then cooled at a rate of 5°C / min to obtain the positive electrode material.

[0030] Example 4

[0031] This embodiment provides a method for preparing an O3-type layered oxide positive electrode material in situ coated with a P2-type metal sodium tellurate solid electrolyte. The preparation method comprises the following steps: 1.1688 g of tellurium dioxide (calculated as tellurium dioxide, the target coating amount is 8%) is added by a wet chemical method. wt ) 2.688g of metal source zinc acetate was dissolved in anhydrous ethanol, and 9.045g of spherical Ni with a particle size D50 of 5.35μm was added to the wet chemical dispersion. y Mn z Fe 1-y-z The (OH)2 precursor and 6.325g of anhydrous sodium carbonate were mixed. The dispersion was heated and stirred using a magnetic stirrer. After the anhydrous ethanol evaporated, the mixed powder was calcined at 900°C for 12 hours in an air atmosphere at a heating rate of 5°C / min and then cooled at a rate of 5°C / min to obtain the positive electrode material.

[0032] Example 5

[0033] This embodiment provides a method for preparing an O3-type layered oxide positive electrode material in situ coated with a P2-type sodium tellurite solid electrolyte. The preparation method is as follows, except that the metal source is magnesium acetate (the corresponding mass of magnesium acetate is ), and the rest are the same as example 2.

[0034] Example 6

[0035] The embodiment provides a preparation method of an O3-type layered oxide positive electrode material in-situ coated with a P2-type metal sodium tellurite solid-state electrolyte, wherein, except that the sodium source is sodium acetate (the mass of the corresponding sodium acetate is ), the rest are the same as example 2.

[0036] Example 7

[0037] The embodiment provides a preparation method of an O3-type layered oxide positive electrode material in-situ coated with a P2-type metal sodium tellurite solid-state electrolyte, wherein, except that the sodium source is sodium hydroxide (the mass of the corresponding sodium hydroxide is ), the rest are the same as example 2.

[0038] Example 8

[0039] The embodiment provides a preparation method of an O3-type layered oxide positive electrode material in-situ coated with a P2-type metal sodium tellurite solid-state electrolyte, wherein, except that the sodium source is sodium acetate (the mass of the corresponding sodium acetate is ), the rest are the same as example 2.

[0040] Example 9

[0041] The embodiment provides a preparation method of an O3-type layered oxide positive electrode material in-situ coated with a P2-type metal sodium tellurite solid-state electrolyte, wherein, except that the high-temperature calcination temperature is 850 DEG C, the rest are the same as example 2.

[0042] Example 10

[0043] The embodiment provides a preparation method of an O3-type layered oxide positive electrode material in-situ coated with a P2-type metal sodium tellurite solid-state electrolyte, wherein, except that the high-temperature calcination temperature is 950 DEG C, the rest are the same as example 2.

[0044] Example 11

[0045] The embodiment provides a preparation method of an O3-type layered oxide positive electrode material in-situ coated with a P2-type metal sodium tellurite solid-state electrolyte, wherein, except that the high-temperature calcination holding time is 8h, the rest are the same as example 2.

[0046] Example 12

[0047] This embodiment provides a preparation method of an O3-type layered oxide positive electrode material in situ coated with a P2-type sodium tellurite metal solid electrolyte. The preparation method is the same as that of Example 2 except that the high-temperature calcination holding time is 15 hours.

[0048] Comparative Example

[0049] This comparative example provides a method for preparing an O3-type layered oxide positive electrode material, the preparation method comprising the following steps: preparing 9.045 g of spherical Ni with a particle size D50 of 5.35 μm by a wet chemical method; y Mn z Fe 1-y-z The (OH)2 precursor was mixed with 5.565 g of anhydrous sodium carbonate. The dispersion was heated and stirred using a magnetic stirrer. After the anhydrous ethanol evaporated, the mixed powder was calcined at 900°C in an air atmosphere at a heating rate of 5°C / min for 12 hours. The temperature was then lowered at a rate of 5°C / min to obtain the positive electrode material.

[0050] X-ray diffraction test was performed on the positive electrode materials obtained in Examples 1 to 4 and the comparative example. The test results are as follows: Figure 1 As shown. Figure 1 All samples exhibit similar O3 phase structures. With increasing coating levels, particularly for 4% and 8% P2@O3 oxides, characteristic diffraction peaks of P2-type Na2Zn2TeO6 and impurity peaks of nickel oxide emerge. The precipitation of the P2 phase demonstrates that the in-situ coating synthesis route using wet chemical impregnation can achieve Na2Zn2TeO6 coating in a single step. However, it also suggests that coating levels of 4% and 8% may not achieve optimal improvements in O3 matrix material properties.

[0051] The positive electrode materials obtained in Example 2 and the comparative example were tested by high resolution transmission electron microscopy (HRTEM). The test results are as follows: Figure 2 shown. Figure 2 The left side of the white dotted line in (a) shows a typical layered structure of O3-type NFM material. On the right side of the white dotted line at the end of the (003) crystal plane family, a crystal structure inconsistent with O3 is shown. Analysis shows that its interplanar spacing is Corresponding to the (014) crystal plane family of the P2 phase. Note that the different lattice fringes in the white dotted ellipse area in the lower left corner are actually just dark areas caused by contrast. To the right of the white dotted line, the lattice fringes of the P2 phase are always continuous. In addition, Figure 2 The HRTEM image of the uncoated O3-type oxide in (b) shows a typical O3 layered structure with no heterogeneous phase formation on the surface, indicating that Example 2 achieved nanoscale primary particle surface coating.

[0052] The positive electrode materials obtained in Examples 1-4 and Comparative Examples were prepared into positive electrode sheets, and sodium ion batteries were prepared with sodium sheets, glass fiber separators and sodium perchlorate electrolyte. The performance of the sodium ion batteries was tested. The test conditions were as follows: at 25°C, 1C charge-discharge steps were carried out for cycling, and after 200 cycles, the discharge capacity of the battery at this time was divided by the discharge capacity of the first cycle, which was the capacity retention rate of the battery after 200 cycles. The rate performance test: the sodium ion batteries prepared from the positive electrode materials obtained in Example 2 and Comparative Example were subjected to rate cycling at 25°C with stepwise rate charge-discharge steps, and the rate performance of the materials was compared. The results of the cycle test are shown in Table 1, and the rate performance is shown in Figure 3

[0053] Table 1:

[0054]

[0055] From Table 1, it can be seen that compared with the uncoated O3-type oxide, all P2@O3-type oxides with different coating ratios in Examples 1-4 showed improved capacity retention rates, but as the coating amount increased, the first cycle capacity showed a decreasing trend. In terms of comprehensive performance, the 2% P2@O3-type oxide in Example 2 showed the best performance. Figure 3 It was shown that the 2% P2@O3-type oxide in Example 2 exhibited very excellent rate performance, and still showed a discharge capacity higher than 95 mAh / g at a current density of 10C (1.3 A / g).

[0056] The above description is only the preferred embodiments used in the present application, and is not intended to limit the present application. Any equivalent replacement, modification and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.​

Claims

1. A P2-type sodium tellurite solid electrolyte in-situ coated O3-type layered oxide positive electrode material, characterized in that The O3-type oxide is a layered metal oxide with a chemical general formula of Na x Ni y Mn z Fe 1-y-z O2, where 0.85 < x < 1.1, 0.1 < y < 0.9, 0.1 < z < 0.

9. The P2-type solid electrolyte layer is also a layered metal oxide with a chemical general formula of Na₂M₂TeO₆ (M is one or more of Zn, Mg, Cu, Ca, Ga, Ni).

2. The O3-type layered oxide cathode material in-situ coated with a P2-type sodium tellurite solid electrolyte according to claim 1, characterized in that The mass ratio of the P2 type solid electrolyte to the O3 type positive electrode material is 1% to 8%.

3. The method for preparing an O3-type layered oxide positive electrode material in-situ coated with a P2-type sodium tellurite solid electrolyte according to claim 1, characterized in that: The process includes the following steps: spherical Ni y Mn z Fe 1-y-z The (OH)2 precursor is uniformly mixed with the sodium source, the coating layer metal source and tellurium dioxide. After the solvent evaporates, the mixture is calcined at a high temperature in a suitable atmosphere and then cooled to obtain the positive electrode material.

4. The preparation method according to claim 3, characterized in that The sodium source is at least one of sodium carbonate, sodium hydroxide, sodium bicarbonate, sodium oxalate, sodium bioxalate, and sodium acetate.

5. The preparation method according to claim 3, characterized in that The metal source of the coating layer is a water or alcohol soluble salt such as acetate or nitrate of each metal.

6. The preparation method according to claim 3, characterized in that The material uniform mixing method is to use spherical Ni y Mn z Fe 1-y-z A wet chemical impregnation method based on the insolubility of the (OH)2 precursor, the solubility of each metal source as described in claim 6, and the solubility of tellurium dioxide.

7. The solvent according to claim 3, characterized in that It is ethanol, water or a mixed solvent of the two in any mass ratio.

8. The method for preparing an O3-type layered oxide positive electrode material in-situ coated with a P2-type sodium tellurite solid electrolyte according to claim 3, characterized in that: The suitable atmosphere is air atmosphere, oxygen atmosphere or a mixture of the two in any volume ratio.

9. The method for preparing an O3-type layered oxide positive electrode material in-situ coated with a P2-type sodium tellurite solid electrolyte according to claim 3, characterized in that: The high-temperature calcination temperature of the mixture is 600-1100° C., the heating rate is 1-20° C. / min, the heat preservation time is 3-24 hours, and the cooling rate is 1-50° C. / min.

10. A sodium ion battery, characterized in that: The sodium ion battery comprises the sodium cathode material according to claims 1 to 9.

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