A sodium-ion battery cathode material with single crystal morphology, a preparation method therefor, and an application thereof

Abstract

The application relates to the technical field of sodium ion batteries, in particular to a single-crystal morphology sodium ion battery positive electrode material and a preparation method and application thereof. w Ni x Fe y Mn 1‑x‑y‑z‑a B z Bi a O2, wherein w<=0.75, 0 The B and Bi elements are co-doped to modify the prepared positive electrode material to have a single-crystal morphology, the performance degradation problem caused by the broken crystal boundary is avoided, the single-crystal morphology sodium battery ternary positive electrode material prepared by the application can still maintain good structural integrity after multiple cycles, and the cycle life is improved. Meanwhile, the electrochemical performances such as the discharge specific capacity, rate performance and cycle retention rate of the sodium battery ternary positive electrode material are also remarkably improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sodium ion batteries, in particular to a single crystal morphology sodium ion battery positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] Compared with the polycrystalline structure ternary positive electrode material, the single crystal structure ternary positive electrode material can realize higher compaction density, thereby bringing higher energy density, and in addition, the single crystal material has better mechanical properties and will not be broken in the process of electrode sheet processing, and will not produce obvious mechanical cracks due to high internal stress in the process of battery cycle. However, the sintered product of the current NiFeMn series sodium battery material is mainly a single crystal-like material, and the single crystal-like positive electrode material can exhibit similar single crystal performance in the macroscopic aspect, but still has a small amount of grain boundaries or defects in the microscopic aspect. In the deep charging state, the single crystal-like positive electrode material may have crystal micro-cracks, which are caused by the structural instability caused by anisotropic lattice shrinkage, thereby causing the electrolyte to penetrate and erode the inside of the secondary particles, resulting in serious side reactions and thus poor electrochemical performance of the positive electrode material. SUMMARY

[0003] Therefore, the technical problem to be solved by the present application is to overcome the defects that the current NiFeMn series sodium battery positive electrode material is mainly single crystal-like morphology, thereby causing poor electrochemical performance, and to provide a single crystal morphology sodium ion battery positive electrode material and a preparation method and application thereof to solve the above problems.

[0004] To achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0005] In a first aspect, the present application provides a single crystal morphology sodium ion battery positive electrode material, which comprises a material with a chemical formula of Na w Ni x Fe y Mn 1-x-y-z-a B z Bi a O2, wherein w≤0.75, 0

[0006] Preferably, the sodium ion battery positive electrode material is a core-shell structure with a core and a coating layer, the core is a material with a chemical formula of Na w Ni x Fe y Mn 1-x-y-z-a B z Bi a O2, and the coating layer is titanium dioxide.

[0007] Preferably, the mass ratio of the core to the coating layer is 100:(0.5-2).

[0008] In a second aspect, the present application also provides a preparation method of the single-crystal morphology sodium-ion battery cathode material, comprising: w Ni x Fe y Mn 1-x-y-z-a B z Bi a O2 material, the sodium source, the nickel source, the iron source, the manganese source, the boron source and the bismuth source are weighed according to the stoichiometric ratio respectively and are uniformly mixed to obtain a mixture; the mixture is subjected to a first sintering treatment to obtain the single-crystal morphology sodium-ion battery cathode material.

[0009] Preferably, the sodium source comprises Na2CO3;

[0010] Preferably, the nickel source comprises NiO;

[0011] Preferably, the iron source comprises Fe2O3;

[0012] Preferably, the manganese source comprises MnO2;

[0013] Preferably, the boron source comprises H3BO3;

[0014] Preferably, the bismuth source comprises Bi2O3.

[0015] Preferably, the uniform mixing treatment lasts for 20-50 min;

[0016] Preferably, the atmosphere of the first sintering treatment is an oxygen-containing atmosphere; optionally, the oxygen-containing atmosphere is air or / and oxygen;

[0017] Preferably, the heat treatment system of the first sintering treatment is: first, the temperature is raised to 600-800℃ at a temperature raising rate of 2-5℃ / min for pre-sintering treatment for 4 h, then the temperature is raised to 950-1000℃ at a temperature raising rate of 2-5℃ / min for calcination treatment for 10-15 h, and then the furnace is naturally cooled down;

[0018] Preferably, after the first sintering treatment, the sintered material is further subjected to crushing and sieving treatment.

[0019] Preferably, the sintered material obtained after the first sintering treatment is further uniformly mixed with titanium dioxide and subjected to a second sintering treatment.

[0020] Preferably, the mass ratio of the sintered material to the titanium dioxide is 100:(0.5-2);

[0021] Preferably, the temperature raising rate of the second sintering treatment is 3℃ / min;

[0022] and / or, the temperature of the second sintering treatment is 700℃;

[0023] and / or, the holding time of the second sintering treatment is 8h;

[0024] and / or, the atmosphere of the second sintering treatment is an oxygen-containing atmosphere; optionally, the oxygen-containing atmosphere is air or / and oxygen.

[0025] Preferably, after the second sintering treatment, the furnace natural cooling, crushing and iron removal treatment are further performed.

[0026] In a third aspect, the application also provides the single crystal morphology sodium-ion battery cathode material or the application of the single crystal morphology sodium-ion battery cathode material prepared by the preparation method of the single crystal morphology sodium-ion battery cathode material in a sodium-ion battery.

[0027] The technical scheme of the application has the following advantages:

[0028] 1. The application provides a single crystal morphology sodium-ion battery cathode material, which comprises a material with a chemical formula of Na w Ni x Fe y Mn 1-x-y-z-a B z Bi a O2, wherein w≤0.75, 0 To solve the problem that the current NiFeMn series of sodium battery cathode materials are mostly single crystal morphology, the application adopts B and Bi elements as doping elements for co-doping modification, so that the prepared cathode material forms a single crystal morphology, and because the single crystal material has no grain boundary, the intergranular cracks are not easy to occur in the charging and discharging process, thereby avoiding the performance degradation problem caused by grain boundary breakage, so that the sodium battery ternary cathode material with single crystal morphology prepared by the application can still maintain good structural integrity after multiple cycles, and the cycle life is improved. At the same time, the electrochemical performance of the sodium battery ternary cathode material of the application, such as the discharge specific capacity, rate performance and cycle retention rate, is also significantly improved.

[0029] 2. In the single crystal morphology sodium-ion battery cathode material of the application, in order to further improve the electrochemical performance of the cathode material, titanium dioxide is coated on the surface of the single crystal morphology sodium-ion battery cathode material, so as to effectively inhibit the side reaction between the cathode material and the electrolyte, reduce the charge transfer impedance, and further improve the cycle stability and rate of the cathode material and other electrochemical performance.

[0030] 3. In the preparation method of the single crystal morphology sodium-ion battery cathode material of the present application, the preparation of the sodium-ion battery cathode material is carried out by a solid phase sintering method, which is simple in operation and easy to mass produce. BRIEF DESCRIPTION OF DRAWINGS

[0031] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0032] Figure 1 is the SEM morphology diagram of a sintered material in Example 1 of the present application;

[0033] Figure 2 is the SEM morphology diagram of a sintered material in Example 2 of the present application;

[0034] Figure 3 is the SEM morphology diagram of a sintered material in Example 3 of the present application;

[0035] Figure 4 is the SEM morphology diagram of a sintered material in Comparative Example 1 of the present application;

[0036] Figure 5 is the SEM morphology diagram of a sintered material in Comparative Example 2 of the present application;

[0037] Figure 6 is the SEM morphology diagram of a sintered material in Comparative Example 3 of the present application. DETAILED DESCRIPTION

[0038] The following examples are provided in order to better further understand the present application, and are not limited to the best mode, and do not constitute a limitation on the content and scope of protection of the present application. Any person under the inspiration of the present application or the combination of the present application with other prior art features can obtain any product identical or similar to the present application, which falls within the scope of protection of the present application.

[0039] The specific experimental steps or conditions not mentioned in the examples can be carried out according to the conventional experimental steps described in the literature in the art or the operation or conditions. The reagents or instruments not mentioned by the manufacturer are conventional reagent products that can be obtained by market purchase.

[0040] Example 1

[0041] The present embodiment provides a preparation method of a single crystal morphology sodium-ion battery cathode material, and the specific steps are as follows:

[0042] 1) According to Na0.70 Ni 0.2 Fe 0.25 Mn 0.53 B 0.01 Bi 0.01 Weigh out H3BO3, NiO, Fe2O3, MnO2, Bi2O3, and Na2CO3 respectively according to the stoichiometric ratio of O2, and mix them in a high-speed mixer for 30 minutes.

[0043] 2) The mixture was placed in an air atmosphere and pre-calcined at 750℃ for 4 hours at a heating rate of 3℃ / min, followed by calcination at 950℃ for 12 hours at a heating rate of 3℃ / min. After natural cooling, it was pulverized and passed through a 325-mesh sieve to obtain Na. 0.70 Ni 0.2 Fe 0.25 Mn 0.53 B 0.01 Bi 0.01 O2-burned materials, their microstructure is as follows Figure 1 As shown;

[0044] 3) According to Na 0.70 Ni 0.2 Fe 0.25 Mn 0.53 B 0.01 Bi 0.01 The O2-calcined material and TiO2 were weighed and mixed in a mass ratio of 100:1, placed in an air atmosphere and sintered at 700℃ for 8 hours at a heating rate of 3℃ / min. After cooling to room temperature, the sodium-ion battery cathode material was obtained by passing it through a 325-mesh sieve and removing iron.

[0045] Example 2

[0046] This embodiment provides a method for preparing a sodium-ion battery cathode material with a single-crystal morphology. The specific steps are as follows:

[0047] 1) According to Na 0.70 Ni 0.2 Fe 0.25 Mn 0.51 B 0.02 Bi 0.02 Weigh out H3BO3, NiO, Fe2O3, MnO2, Bi2O3, and Na2CO3 respectively according to the stoichiometric ratio of O2, and mix them in a high-speed mixer for 50 minutes.

[0048] 2) The mixture was placed in an air atmosphere and pre-calcined at 800℃ for 4 hours at a heating rate of 5℃ / min, followed by calcination at 1000℃ for 10 hours at a heating rate of 5℃ / min. After natural cooling, it was pulverized and passed through a 325-mesh sieve to obtain Na. 0.70 Ni0.2 Fe 0.25 Mn 0.51 B 0.02 Bi 0.02 O2-burned materials, their microstructure is as follows Figure 2 As shown;

[0049] 3) According to Na 0.70 Ni 0.2 Fe 0.25 Mn 0.51 B 0.02 Bi 0.02 The O2-calcined material and TiO2 were weighed and mixed in a mass ratio of 100:0.5, placed in an air atmosphere, and sintered at 700℃ for 8 hours at a heating rate of 5℃ / min. After cooling to room temperature, the sodium-ion battery cathode material was obtained by passing it through a 325-mesh sieve and removing iron.

[0050] Example 3

[0051] This embodiment provides a method for preparing a sodium-ion battery cathode material with a single-crystal morphology. The specific steps are as follows:

[0052] 1) According to Na 0.70 Ni 0.2 Fe 0.25 Mn 0.47 B 0.04 Bi 0.04 Weigh out H3BO3, NiO, Fe2O3, MnO2, Bi2O3, and Na2CO3 respectively according to the stoichiometric ratio of O2, and mix them in a high-speed mixer for 20 minutes.

[0053] 2) The mixture was placed in an air atmosphere and pre-calcined at 600℃ for 4 hours at a heating rate of 2℃ / min, followed by calcination at 950℃ for 15 hours at a heating rate of 2℃ / min. After natural cooling, it was pulverized and passed through a 325-mesh sieve to obtain Na. 0.70 Ni 0.2 Fe 0.25 Mn 0.47 B 0.04 Bi 0.04 O2-burned materials, their microstructure is as follows Figure 3 As shown;

[0054] 3) According to Na 0.70 Ni 0.2 Fe 0.25 Mn 0.47 B 0.04 Bi 0.04The O2-calcined material and TiO2 were weighed and mixed in a mass ratio of 100:2. The mixture was placed in an air atmosphere and sintered at 700℃ for 8 hours at a heating rate of 2℃ / min. After cooling to room temperature, the sodium-ion battery cathode material was obtained by passing it through a 325-mesh sieve and removing iron.

[0055] Example 4

[0056] This embodiment provides a method for preparing a sodium-ion battery cathode material with a single crystal morphology. The difference between this method and Example 1 is that titanium dioxide coating is not performed (i.e., step 3 is not performed), while other conditions are the same as in Example 1.

[0057] Comparative Example 1

[0058] This comparative example provides a method for preparing a sodium-ion battery cathode material with a single-crystal morphology. The specific steps are as follows:

[0059] 1) According to Na 0.70 Ni 0.2 Fe 0.25 Mn 0.55 Weigh out NiO, Fe2O3, MnO2, and Na2CO3 according to their stoichiometric ratios for O2, and mix them in a high-speed mixer for 30 minutes.

[0060] 2) The mixture was placed in an air atmosphere and pre-calcined at 750℃ for 4 hours at a heating rate of 3℃ / min, followed by calcination at 950℃ for 12 hours at a heating rate of 3℃ / min. After natural cooling, it was pulverized and passed through a 325-mesh sieve to obtain Na. 0.70 Ni 0.2 Fe 0.25 Mn 0.55 O2-burned materials, their microstructure is as follows Figure 4 As shown;

[0061] 3) According to Na 0.70 Ni 0.2 Fe 0.25 Mn 0.55 The O2-calcined material and TiO2 were weighed and mixed in a mass ratio of 100:1, placed in an air atmosphere and sintered at 700℃ for 8 hours at a heating rate of 3℃ / min. After cooling to room temperature, the sodium-ion battery cathode material was obtained by passing it through a 325-mesh sieve and removing iron.

[0062] Comparative Example 2

[0063] This comparative example provides a method for preparing a sodium-ion battery cathode material with a single-crystal morphology. The specific steps are as follows:

[0064] 1) According to Na 0.70 Ni 0.2 Fe 0.25Mn 0.53 B 0.02 H3BO3, NiO, Fe2O3, MnO2, Na2CO3 were weighed according to the stoichiometric ratio of Na

[0065] 2) The mixture was placed in an air atmosphere and heated to 750 DEG C at a heating rate of 3 DEG C / min for pre-burning treatment for 4h, and then heated to 950 DEG C at a heating rate of 3 DEG C / min for calcination treatment for 12h, after natural cooling, crushing, and passing through a 325 mesh sieve, Na 0.70 Ni 0.2 Fe 0.25 Mn 0.53 B 0.02 O2 one-fired material, and the micro-morphology thereof is shown in Figure 5 ;

[0066] 3) Na 0.70 Ni 0.2 Fe 0.25 Mn 0.53 B 0.02 O2 one-fired material and TiO2 were weighed and mixed according to a mass ratio of 100:1, and placed in an air atmosphere and heated to 700 DEG C at a heating rate of 3 DEG C / min for sintering treatment for 8h, cooled to room temperature, passed through a 325 mesh sieve, and after removing iron, a sodium battery positive electrode material was obtained.

[0067] Comparative Example 3

[0068] The present comparative example provides a preparation method of a sodium ion battery positive electrode material with a single crystal morphology, and the specific steps are as follows:

[0069] 1) Na 0.70 Ni 0.2 Fe 0.25 Mn 0.53 Bi 0.02 H3BO3, NiO, Fe2O3, MnO2, Na2CO3 were weighed according to the stoichiometric ratio of Na

[0070] 2) The mixture was placed in an air atmosphere and heated to 750 DEG C at a heating rate of 3 DEG C / min for pre-burning treatment for 4h, and then heated to 950 DEG C at a heating rate of 3 DEG C / min for calcination treatment for 12h, after natural cooling, crushing, and passing through a 325 mesh sieve, Na 0.70 Ni 0.2 Fe 0.25 Mn 0.53 Bi 0.02 O2 one-fired material, and the micro-morphology thereof is shown in Figure 6 ;

[0071] 3) Na0.70 Ni 0.2 Fe 0.25 Mn 0.53 Bi 0.02 The O2-calcined material and TiO2 were weighed and mixed in a mass ratio of 100:1, placed in an air atmosphere and sintered at 700℃ for 8 hours at a heating rate of 3℃ / min. After cooling to room temperature, the sodium-ion battery cathode material was obtained by passing it through a 325-mesh sieve and removing iron.

[0072] Test Example 1

[0073] The sodium-ion battery cathode materials prepared in Examples 1-3 and Comparative Examples 1-3 were used as the main materials for electrical performance testing. The electrical performance testing conditions were as follows: a slurry was prepared at a mass ratio of 95 (main material): 2.5 (PVDF): 2.5 (SP) (N-methylpyrrolidone was used as a dispersant (the amount of dispersant was 10 times the mass of PVDF)) and coated to form an electrode sheet (coating amount 6 mg / cm³). 2 The CR2032 coin cell is assembled from a button cell using sodium metal as the counter electrode, glass fiber as the separator, and a 1 mol / L NaPF6 solution of ethylene carbonate (EC) / dimethyl carbonate (DMC) (volume ratio 1:1) as the electrolyte. The positive electrode, sodium sheet, separator, gasket, and spring are placed in the button cell to form the CR2032 coin cell.

[0074] The button cells were placed in the Blue Electric testing system for electrical performance testing. The electrical performance testing parameters were set as follows: voltage range 2.0V-4.5V; capacity testing was performed in the first cycle using 0.1C / 0.1C charge / discharge to obtain the discharge specific capacity (0.1C); then rate performance was evaluated using 0.2C / 0.2C, 0.5C / 0.5C, and 1C / 1C charge / discharge tests, with rate performance calculated as discharge capacity at 1C / discharge capacity at 0.1C; finally, cycle performance was evaluated by 50 cycles at 1C / 1C to obtain the capacity retention rate after 50 cycles. The test results are shown in Table 1.

[0075] Table 1

[0076]

[0077] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A single-crystalline morphology sodium-ion battery cathode material, characterized in that, It includes a material of the formula Na w Ni x Fe y Mn 1-x-y-z-a B z Bi a O2, wherein w < 0.75, 0 < x < 0.25, 0 < y < 0.3, 0 < z < 0.05, 0 < a < 0.

05.

2. The sodium-ion battery cathode material of claim 1, wherein, The sodium ion battery cathode material is a core-shell structure with a core and a coating layer, the core is a material with a chemical formula of Na w Ni x Fe y Mn 1-x-y-z-a B z Bi a O2, and the coating layer is titanium dioxide.

3. The sodium-ion battery cathode material of claim 2, wherein, The mass ratio of the core to the coating layer is 100: (0.5-2).

4. A method of preparing a single-crystalline morphology sodium-ion battery cathode material according to any one of claims 1-3, characterized in that, The sodium source comprises Na2CO3. According to Na w Ni x Fe y Mn 1-x-y-z-a B z Bi a The stoichiometric ratio of O2 material is weighed respectively sodium source, nickel source, iron source, manganese source, boron source, bismuth source and mixed to obtain a mixture; the first sintering treatment is carried out on the mixture to obtain a single crystal morphology sodium ion battery positive electrode material.

5. The preparation method according to claim 4, characterized in that, The nickel source comprises NiO. The iron source comprises Fe2O3. The manganese source comprises MnO2. The boron source comprises H3BO3. The bismuth source comprises Bi2O3. The mixing time is 20-50 min.

6. The production method according to claim 4 or 5, characterized by, The first sintering treatment is carried out in an oxygen-containing atmosphere. The first sintering treatment is carried out at a temperature of 600-800℃ for 4 h, and then at a temperature of 950-1000℃ for 10-15 h. The sintered material obtained after the first sintering treatment is further mixed with titanium dioxide and subjected to a second sintering treatment. The mass ratio of the sintered material to the titanium dioxide is 100: (0.5-2).

7. The production method according to claim 6, characterized by, The second sintering treatment is carried out at a temperature of 700℃.

8. The preparation method according to claim 4, characterized in that, The second sintering treatment is carried out for 8 h.

9. The preparation method according to claim 8, characterized in that, The second sintering treatment is carried out in an oxygen-containing atmosphere. The second sintering treatment is carried out in air or / and oxygen. The sintered material obtained after the second sintering treatment is further subjected to natural cooling, crushing and iron removal.

12. The single-crystal-shaped sodium-ion battery cathode material prepared by the method of any one of claims 1-3 or 4-11, and application of the single-crystal-shaped sodium-ion battery cathode material in a sodium-ion battery. ​ 10. The method of claim 9, wherein, ​ 11. The preparation method according to claim 8, characterized in that, ​ ​

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