A cathode material for sodium-ion batteries and a preparation method thereof

Abstract

The present invention discloses a cathode material for a sodium-ion battery and a preparation method thereof. The cathode material includes a mother nucleus, a first coating layer, and a second coating layer. The mother nucleus is a polyanion compound, the first coating layer is a carbon layer generated after the pyrolysis and carbonization of an organic sodium compound precursor, and the second coating layer is nano sodium aluminosilicate particles. The first coating layer uniformly and completely coats the surface of the mother nucleus and the second coating layer particles, and the second coating layer particles uniformly and completely coat the mother nucleus already coated with the first coating layer. The first coating layer and the second coating layer particles act synergistically to reduce the electron and ion conduction distances and structural stress during the charge and discharge process of the material and regulate the grain size of the material, effectively improving the capacity, rate performance, cycle performance, and tap density of the material. The second coating layer can improve the grinding efficiency during the grinding process in the material processing and preparation process and reduce the sintering temperature and shorten the sintering cycle during the sintering process, reduce energy consumption, and improve the processing and preparation efficiency, thereby reducing the material preparation cost.

Description

Technical Field

[0001] The present invention belongs to the field of cathode materials for sodium-ion batteries, and particularly relates to a cathode material for sodium-ion batteries and a preparation method thereof. Background Art

[0002] With the rapid development of the application of lithium-ion batteries in new energy electric vehicles, energy storage and other fields, the supply and demand scale of lithium-ion battery cathode materials has been continuously expanding. However, lithium resources, which are essential for the preparation of lithium-ion battery cathode materials, have relatively few reserves and uneven distributions, thus restricting the sustainable development of the industry. Sodium-ion batteries are one of the effective supplementary solutions for the application of lithium-ion batteries. Compared with lithium resources, sodium resources are more abundant and evenly distributed globally, and theoretically, the sodium-ion battery system has lower manufacturing costs and a wider range of application scenarios.

[0003] At present, compared with the highly mature lithium-ion battery system in terms of industrialization scale, sodium-ion batteries have better safety performance, high and low temperature performance, and theoretical cost advantages. However, their energy density is relatively low and the actual cost is still high. Optimizing the preparation method of cathode materials to improve the comprehensive performance of materials and reduce the material preparation cost is one of the necessary methods to improve the comprehensive performance of the sodium-ion battery system and reduce the comprehensive cost of the sodium-ion battery system. Summary of the Invention

[0004] The present invention aims to provide a cathode material for sodium-ion batteries and a preparation method thereof. Through the synergistic effect of the first coating layer and the second coating particles, the electrochemical performance and energy density of the material are improved; and by introducing the second coating, the processing and preparation efficiency of the material is improved, the energy consumption is reduced, thereby reducing the material preparation cost.

[0005] To this end, in the first aspect of the present invention, a cathode material for sodium-ion batteries is provided. The cathode material includes a mother nucleus, a first coating, and a second coating. The mother nucleus is a polyanion compound, the first coating is a carbon layer generated after the pyrolysis and carbonization of an organic sodium compound precursor, the second coating is nano sodium aluminosilicate particles, the first coating layer uniformly and completely coats the surface of the mother nucleus and the second coating particles, and the second coating particles uniformly and completely coat the surface of the mother nucleus already coated with the first coating layer.

[0006] Preferably, the structural formula of the polyanion compound mother nucleus is Na x M y (XO4) z (P2O7) w , where M is a transition metal element, X is a non-metal element, 1 ≤ x ≤ 4, 1 ≤ y ≤ 3, 10 ≤ z ≤ 3, 0 ≤ w ≤ 1.

[0007] Preferably, the Na x M y(XO4) z (P2O7) w The particle size of the mother nucleus is 0.8 - 1.8 um.

[0008] Preferably, the transition metal element M is one of Fe and V, and the non-metal element X is P.

[0009] Preferably, the first coating precursor organic sodium compound is sodium alginate (C6H7NaO6) n 。

[0010] Preferably, the organic sodium compound (C6H7NaO6) n has an n value of 1 - 12.

[0011] Preferably, the carbon layer thickness generated after the pyrolysis and carbonization of the organic sodium compound precursor is 0.5 - 1.0 nm.

[0012] Preferably, the second coating nano sodium aluminosilicate particles are NaAlSi3O8.

[0013] Preferably, the particle size of the NaAlSi3O8 nanoparticles is 50 - 200 nm.

[0014] Second, the present invention provides a method for preparing a cathode material for a sodium-ion battery. The preparation method includes: dissolving the first coating precursor (C6H7NaO6) n in water to form a dispersion, adding a first sodium source, a second sodium source, an iron source or a vanadium source, etc. to the first coating dispersion to obtain slurry I; adding the second coating NaAlSi3O8 to slurry I for dispersion and grinding to obtain slurry II; drying slurry II and then sintering it under atmosphere protection to obtain the cathode material.

[0015] Preferably, the first sodium source is at least one of sodium carbonate, sodium sulfate, sodium bicarbonate, sodium hydroxide, and sodium oxalate.

[0016] Preferably, the second sodium source is sodium pyrophosphate.

[0017] Preferably, the iron source is at least one of iron phosphate, ferrous sulfate, ferric pyrophosphate, and ferrous oxalate; the vanadium source is at least one of vanadium trioxide, vanadium pentoxide, and sodium metavanadate.

[0018] Preferably, the mass ratio of the iron source or vanadium source, the first sodium source, the second sodium source, the first coating precursor (C6H7NaO6) n to the second coating NaAlSi3O8 is 1:0.18 - 0.22:0.28 - 0.32:0.08 - 0.16:0.002 - 0.005.

[0019] Preferably, the particle size D50 of the slurry II is 0.3 to 0.5 um.

[0020] Preferably, the sintering temperature is 300 to 500 °C, and the sintering time is 3 to 5.

[0021] In a third aspect, the present invention provides a sodium-ion battery, which comprises the positive electrode material of the sodium-ion battery of the present invention or the positive electrode material of the sodium-ion battery prepared by the preparation method of the present invention.

[0022] Compared with the prior art, the method of the present invention has the following remarkable advantages:

[0023] Through the synergistic effect of the first coating layer and the second coating particles, the present invention can reduce the electron and ion conduction distances and structural stress during the charge and discharge process of the material and regulate the grain size of the material, effectively improving the capacity, rate performance, cycle performance and tap density of the material. The second coating can improve the grinding efficiency during the grinding process of the material preparation and reduce the sintering temperature and shorten the sintering cycle during the sintering process, reducing energy consumption and improving the processing efficiency, thereby reducing the material preparation cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the positive electrode material of the sodium-ion battery of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided so that the disclosure of the present invention can be more thorough and comprehensive.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0027] The present invention first discloses a positive electrode material for a sodium-ion battery, which comprises a mother nucleus, a first coating and a second coating. The mother nucleus is a polyanion compound, the first coating is a carbon layer produced by pyrolysis and carbonization of an organic sodium compound precursor, and the second coating is nano sodium aluminosilicate particles. The first coating layer uniformly and completely coats the surface of the mother nucleus and the second coating particles, and the second coating particles uniformly and completely coat the mother nucleus already coated with the first coating layer.

[0028] Specifically, the structural formula of the polyanion compound mother nucleus is Na x M y(XO4) z (P2O7) w , wherein M is a transition metal element, X is a non-metal element, 1 ≤ x ≤ 4, 1 ≤ y ≤ 3, 10 ≤ z ≤ 3, 0 ≤ w ≤ 1.

[0029] Specifically, the Na x M y (XO4) z (P2O7) w The particle size of the mother nucleus is 0.8 - 1.8 um.

[0030] Specifically, the transition metal element M is one of Fe and V, and the non-metal element X is P.

[0031] Specifically, the first coating precursor organic sodium compound is sodium alginate (C6H7NaO6) n .

[0032] Specifically, the n value of the organic sodium compound (C6H7NaO6) n is 1 - 12.

[0033] Specifically, the carbon layer thickness generated after the pyrolysis and carbonization of the organic sodium compound precursor is 0.5 - 1.0 nm.

[0034] Specifically, the second coating nano sodium aluminosilicate particles are NaAlSi3O8.

[0035] Specifically, the particle size of the NaAlSi3O8 nanoparticles is 50 - 200 nm.

[0036] In an embodiment of the present invention, a method for preparing a cathode material for a sodium-ion battery is also provided, including the following steps:

[0037] (1) Dissolve the first coating precursor (C6H7NaO6) n in water to form a dispersion, and add the first sodium source, the second sodium source, the iron source or the vanadium source, etc. to the first coating dispersion to obtain slurry I;

[0038] (2) Add the second coating NaAlSi3O8 to slurry I for dispersion and grinding to obtain slurry II;

[0039] (3) Dry slurry II and then sinter it under atmosphere protection to obtain the cathode material.

[0040] Wherein, the first sodium source is at least one of sodium carbonate, sodium sulfate, sodium bicarbonate, sodium hydroxide, and sodium oxalate.

[0041] Wherein, the second sodium source is sodium pyrophosphate.

[0042] Among them, the iron source is at least one of iron phosphate, ferrous sulfate, ferric pyrophosphate, and ferrous oxalate; the vanadium source is at least one of vanadium trioxide, vanadium pentoxide, and sodium metavanadate.

[0043] Further, the mass ratio of the iron source or vanadium source, the first sodium source, the second sodium source, the first coating precursor (C6H7NaO6) n , and the second coating NaAlSi3O8 is 1:0.18 - 0.22:0.28 - 0.32:0.08 - 0.16:0.002 - 0.005.

[0044] Preferably, the particle size D50 of the slurry II is 0.3 - 0.5 um.

[0045] Preferably, the sintering temperature is 300 - 500 °C, and the sintering time is 3 - 5 h.

[0046] To better illustrate the purpose, technical solution, and beneficial effects of the present invention, the present invention will be further clearly and completely described below in conjunction with specific embodiments. The following implementation methods are further explanatory descriptions of the present invention and should not be regarded as limitations on the present invention.

[0047] Example 1

[0048] Dissolve 800 g of (C6H7NaO6)5 in 15 kg of pure water to form a dispersion liquid, and then add 10 kg of iron phosphate, 1.8 kg of sodium carbonate, and 2.8 kg of sodium pyrophosphate to the dispersion liquid and stir to disperse evenly to obtain slurry I; add 20 g of NaAlSi3O8 to slurry I for dispersion, grind to D50 = 0.35 um to obtain slurry II; dry slurry II and sinter at 350 °C for 4 h in a nitrogen protection atmosphere to prepare the positive electrode material.

[0049] Example 2

[0050] Dissolve 820 g of (C6H7NaO6)5 in 16 kg of pure water to form a dispersion liquid, and then add 10 kg of iron phosphate, 1.9 kg of sodium carbonate, and 3 kg of sodium pyrophosphate to the dispersion liquid and stir to disperse evenly to obtain slurry I; add 22 g of NaAlSi3O8 to slurry I for dispersion, grind to D50 = 0.4 um to obtain slurry II; dry slurry II and sinter at 300 °C for 4.5 h in a nitrogen protection atmosphere to prepare the positive electrode material.

[0051] Example 3

[0052] Dissolve 900 g of (C6H7NaO6)5 in 18 kg of pure water to form a dispersion. Then, add 10 kg of iron phosphate, 2 kg of sodium carbonate, and 2.9 kg of sodium pyrophosphate to the dispersion and stir to disperse evenly to obtain Slurry I; add 22 g of NaAlSi3O8 to Slurry I for dispersion, grind to D50 = 0.42 um to obtain Slurry II; dry Slurry II and sinter at 400 °C for 3.5 h in a nitrogen protection atmosphere to prepare the positive electrode material.

[0053] Example 4

[0054] Dissolve 1000 g of (C6H7NaO6)5 in 18 kg of pure water to form a dispersion. Then, add 10 kg of iron phosphate, 2.1 kg of sodium carbonate, and 3.1 kg of sodium pyrophosphate to the dispersion and stir to disperse evenly to obtain Slurry I; add 22 g of NaAlSi3O8 to Slurry I for dispersion, grind to D50 = 0.42 um to obtain Slurry II; dry Slurry II and sinter at 450 °C for 3 h in a nitrogen protection atmosphere to prepare the positive electrode material.

[0055] Comparative Example 1

[0056] 10 kg of FePO4, 5.2 kg of Na2CO3, and 1.5 kg of C6H 12 O6 are added to 16 kg of pure water, stirred well, and then ground to obtain a mixed slurry with D50 = 0.52 um; the mixed slurry is dried and sintered at 560 °C for 10 h in a nitrogen atmosphere to prepare the positive electrode material for a sodium-ion battery.

[0057] Comparative Example 2

[0058] 10 kg of FePO4, 5.5 kg of Na2CO3, and 1.6 kg of C6H 12 O6 are added to 18 kg of pure water, stirred well, and then ground to obtain a mixed slurry with D50 = 0.48 um; the mixed slurry is dried and sintered at 580 °C for 8 h in a nitrogen atmosphere to prepare the positive electrode material for a sodium-ion battery.

[0059] Comparative Example 3

[0060] 12 kg of FePO4, 6 kg of Na2CO3, and 1.8 kg of C6H 12 O6 are added to 20 kg of pure water, stirred well, and then ground to obtain a mixed slurry with D50 = 0.54 um; the mixed slurry is dried and sintered at 600 °C for 7 h in a nitrogen atmosphere to prepare the positive electrode material for a sodium-ion battery.

[0061] Comparative Example 4

[0062] Dissolve 800 g of (C6H7NaO6)5 in 15 kg of pure water to form a dispersion, and then add 10 kg of iron phosphate, 1.8 kg of sodium carbonate, and 2.8 kg of sodium pyrophosphate to the dispersion and stir to disperse evenly to obtain Slurry I; grind it to D50 = 0.35 um to obtain the slurry; dry the slurry and sinter it at 560 °C for 10 h in a nitrogen protection atmosphere to obtain the positive electrode material.

[0063] The positive electrode materials obtained in Examples 1-4 and Comparative Examples 1-4 were respectively mixed with SP and PVDF in a ratio of 95.5%:2.5%:2%, coated on a carbon-coated aluminum foil current collector, and respectively matched with a hard carbon and a graphite negative electrode to prepare full cells of the same specification model. The positive electrode materials and the full cells prepared in the examples and comparative examples were respectively tested for relevant performances, and the results are shown in Table 1.

[0064] Table 1 Related test results

[0065]

[0066] From the test results in Table 1, it can be seen that the sodium-ion battery positive electrode materials prepared in Examples 1-4 have higher discharge specific capacity, better rate performance, better cycling performance, higher compaction and higher energy density.

[0067] Compared with Comparative Examples 1-4, in the present invention, through the synergistic effect of the first coating layer (the carbon layer generated after the pyrolysis and carbonization of the (C6H7NaO6)5 precursor) and the second coating body NaAlSi3O8 particles, it is possible to reduce the electron and ion conduction distances and structural stress during the charge and discharge process of the material and regulate the grain size of the material, effectively improving the capacity, rate performance, cycling performance and compaction density of the material. The use of the second coating body NaAlSi3O8 particles can effectively reduce the sintering temperature during the sintering treatment process and shorten the sintering cycle, thereby significantly reducing energy consumption, improving the preparation and processing efficiency, and reducing the preparation cost of the material.

[0068] At the same time, in Comparative Example 4, the inventors found that when NaAlSi3O8 was not added, the time required to grind the slurry to the specified particle size was significantly longer than that in Example 1, and the grinding efficiency was low. The performance data such as the discharge specific capacity, rate performance, cycling performance, compaction and energy density of the material prepared using (C6H7NaO6)5 as the first coating precursor were improved compared with Comparative Examples 1-3, but were not as good as the positive electrode material in Example 1, which further reflects the synergistic effect of the first coating layer (the carbon layer generated after the pyrolysis and carbonization of the (C6H7NaO6)5 precursor) and the second coating body NaAlSi3O8 particles.

[0069] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A cathode material for a sodium-ion battery, characterized in that, It includes a mother nucleus, a first coating layer, and a second coating. The mother nucleus is a polyanionic compound. The first coating layer is a carbon layer produced by pyrolysis and carbonization of an organic sodium compound precursor. The second coating is nano sodium aluminosilicate particles. The first coating layer uniformly and completely coats the surface of the mother nucleus and the second coating particles. The second coating particles uniformly and completely coat the mother nucleus already coated with the first coating layer; The structural formula of the polyanion compound mother nucleus is Na x M y (XO4) z (P2O7) w , where M is a transition metal element selected from one of Fe and V, X is a non-metal element P, 1 ≤ x ≤ 4, 1 ≤ y ≤ 3, 1 ≤ z ≤ 3, 0 ≤ w ≤ 1; The organic sodium compound precursor is sodium alginate (C6H7NaO6) n , where the value of n is 1 to 12; The nano sodium aluminosilicate particles are NaAlSi3O8 nanoparticles.

2. The cathode material for a sodium-ion battery according to claim 1, characterized in that, The described Na x M y (XO4) z (P2O7) w The core particle size is 0.8 to 1.8 μm.

3. The cathode material for a sodium-ion battery according to claim 1, characterized in that, The thickness of the carbon layer produced by pyrolysis and carbonization of the organic sodium compound precursor is 0.5 - 1.0 nm.

4. A cathode material for a sodium-ion battery according to claim 1, characterized in that, The particle size of the NaAlSi3O8 nanoparticles is 50 - 200 nm.

5. The preparation method of a cathode material for a sodium-ion battery according to claim 1, characterized in that, It includes the following steps: (1) Dissolve the first coating precursor sodium alginate (C6H7NaO6) in water to form a dispersion, and add the first sodium source, the second sodium source, and the iron source or vanadium source to the first coating precursor dispersion to obtain Slurry I; n ​ (2) Add the second coating NaAlSi3O8 to slurry I for dispersion and grinding to obtain slurry II; (3) Dry slurry II and then sinter it under atmosphere protection to obtain the positive electrode material; The first sodium source is at least one of sodium carbonate, sodium sulfate, sodium bicarbonate, sodium hydroxide, and sodium oxalate; The second sodium source is sodium pyrophosphate; The iron source is at least one of iron phosphate, ferrous sulfate, ferric pyrophosphate, and ferrous oxalate; the vanadium source is at least one of vanadium trioxide, vanadium pentoxide, and sodium metavanadate.

6. The preparation method of a sodium ion battery cathode material according to claim 5, characterized in that, The mass ratio of the iron source or vanadium source, the first sodium source, the second sodium source, the first coating precursor sodium alginate (C6H7NaO6) n , and the second coating NaAlSi3O8 is 1:0.18 - 0.22:0.28 - 0.32:0.08 - 0.16:0.002 - 0.

005.

7. The preparation method of a cathode material for a sodium-ion battery according to claim 5, wherein, The particle size D50 of slurry II is 0.3 - 0.5 um.

8. The preparation method of a sodium ion battery cathode material according to claim 5, characterized in that, The sintering temperature is 300 - 500 °C, and the sintering time is 3 - 5 h.

9. A sodium-ion battery, characterized in that, It includes the positive electrode material for a sodium ion battery described in any one of claims 1 - 4 or the positive electrode material for a sodium ion battery prepared by the preparation method described in any one of claims 5 - 8.

Images