Sodium-ion positive electrode material, preparation method therefor, and use thereof

Abstract

The present disclosure provides a sodium-ion positive electrode material, a preparation method therefor, and a use thereof. The sodium-ion positive electrode material comprises an O3-type layered oxide and an O'3-type layered oxide. The chemical formula of the sodium-ion positive electrode material is O3-NaxNiyFezMntMhQnO2&O'3-NaaNibFecMneMfQgO2. M is a +2-valent metal element, and Q is a +4-valent metal element. The present disclosure reduces interface side reactions by means of surface doping using a positive divalent metal element, and by means of doping the O3-O'3 phase using a positive tetravalent metal element, inhibits manganese dissolution of the phase during a cycle and inhibits manganese dissolution of O'3 after the O3-O'3 phase transformation of the material, thereby improving the cycle performance of the material.

Description

A sodium ion positive electrode material and its preparation method and application Technical Field

[0001] The present disclosure belongs to the technical field of sodium ion batteries, for example, a sodium ion positive electrode material and a preparation method and application thereof. Background Art

[0002] With the arrival of the bottleneck period in the development of lithium-ion battery technology and the constraint of lithium resources, the cost of lithium secondary batteries is very high, which limits their application in the field of large-scale power storage. Sodium-ion batteries are a type of secondary battery that mainly rely on the movement of sodium ions between the positive and negative electrodes to work, similar to the working principle of lithium-ion batteries. Sodium reserves are abundant and widely distributed on the earth, which can meet the challenges of resource supply. Its cost-effectiveness advantage is very prominent. Among them, sodium-ion layered cathode materials not only have cost advantages, but also have excellent energy density, thermal stability, low-temperature resistance, and fast charging and discharging, which are favored by the market.

[0003] O3 type oxide has more sodium content and its gram capacity is higher, but the Na content of O3 type oxide is + The diffusion channel is tortuous and the structure is relatively unstable. At the same time, studies have found that the O3 type is prone to undergoing an O3-O'3 phase transition during the charge and discharge process. While the O'3 structure often has a higher initial specific capacity, it suffers from poor reversibility due to a strong Jan-Taylor effect. Therefore, improving the structural stability of the O'3 phase is theoretically beneficial to improving the structural stability of the O3 oxide. However, in reality, the O'3 phase is caused by a phase transition during the charge and discharge process, making it difficult to directly improve the structural stability of the O'3 phase during material preparation, thereby achieving the goal of further improving the structural stability of the O3 phase.

[0004] CN115602814A discloses a positive electrode material, a sodium ion battery, and an electrical device. The positive electrode material includes positive electrode material particles having a core-shell structure, wherein the core includes a P2-phase layered oxide and the shell includes an O3-phase layered oxide.

[0005] CN113937279A discloses a positive electrode material, a preparation method thereof, and a sodium-ion battery. The positive electrode material is a layered oxide with an O3 structure. In conventional sodium-ion batteries, potassium, copper, and rare earth elements are simultaneously doped, and the doping amounts are controlled within the aforementioned ranges. The interaction between these elements enhances sodium ion migration, improves the structural stability of the material, and significantly increases the structural stability and charge / discharge capacity of the battery.

[0006] The positive electrode materials described in the above solutions have the problems of poor structural stability or poor cycle stability, which limits their application in practice.

[0007] Summary of the Invention

[0008] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0009] The purpose of the present disclosure is to provide a sodium ion positive electrode material and its preparation method and application. The present disclosure suppresses the manganese dissolution of O3-O'3 phase during the cycle process by surface doping with positive divalent metal elements and bulk doping with positive tetravalent metal elements, thereby suppressing the manganese dissolution of O'3 after the O3-O'3 phase transformation of the material, thereby improving the cycle performance of the material.

[0010] To achieve this disclosure purpose, the present disclosure adopts the following technical solutions:

[0011] In a first aspect, the present disclosure provides a sodium ion positive electrode material, wherein the sodium ion positive electrode material comprises an O3 type layered oxide and an O'3 type layered oxide, and the chemical formula of the sodium ion positive electrode material is O3-Na x Ni y Fe z Mn t M h Q n O2&O'3-Na a Ni b Fe c Mn e M f Q g O2, wherein 0.76≤(x+a)≤1.03, 0≤(y+b)≤1, 0≤(z+c)≤0.5, 0≤(t+e)≤1, 0.05≤(h+f)≤0.25, 0.005≤(n+g)≤0.1, M is a +2 valent metal element, and Q is a +4 valent metal element.

[0012] The disclosed embodiment suppresses the manganese dissolution of O3-O'3 phase during the cycle by surface doping with positive divalent metal elements and bulk doping with positive tetravalent metal elements, thereby suppressing the manganese dissolution of O'3 after the O3-O'3 phase transformation, thereby improving the cycle performance of the material.

[0013] In one embodiment, M includes any one or a combination of at least two of Zn, Cu, Mg, Ca, Sr or Ba, preferably any one or a combination of at least two of Zn, Cu, Mg or Sr.

[0014] In one embodiment, Q includes Zr and / or Ti.

[0015] In one embodiment, the sodium ion positive electrode material is layered.

[0016] In one embodiment, based on 100% mass of the sodium ion positive electrode material, the mass fraction of the O'3-type layered oxide is 0.1-10%, for example, 0.1%, 0.5%, 1%, 2%, 5% or 10%.

[0017] In a second aspect, an embodiment of the present disclosure provides a method for preparing the sodium ion positive electrode material as described in the first aspect, the preparation method comprising the following steps:

[0018] (1) mixing oxides of Ni, Fe, Mn and Q with a sodium source and sintering them once to obtain a single-fired material;

[0019] (2) The primary sintered material and the oxide of M are mixed, and after secondary sintering, the temperature is lowered to a holding temperature for holding, and immediately quenched after the holding is completed to obtain the sodium ion positive electrode material.

[0020] During the preparation process of the sodium ion positive electrode material described in the embodiment of the present disclosure, +4 valent element doping is performed in advance. The doping of +4 metal elements improves the structural stability of the monoclinic O'3 phase, weakens the Jan-Taylor effect, and thus improves the capacity and cycle stability of the material. The single-fired material doped with the +4 valent element is mixed with a +2 valent metal source and sintered. The O'3 phase is formed by surface doping with +2 metal elements and heat preservation in the cooling stage. The coexistence of O3-O'3 is maintained at room temperature by a quenching method of extremely rapid cooling to prepare an O3-O'3 composite phase with a certain O'3 phase content. At the same time, due to the initial stable monoclinic O'3 phase, the O3 phase may be directionally induced to convert into a more stable O'3 phase during the charge and discharge process, so that the material as a whole has excellent capacity and cycle retention rate.

[0021] In one embodiment, the primary sintering temperature in step (1) is 800-1000°C, for example, 800°C, 850°C, 900°C, 950°C or 100°C.

[0022] In one embodiment, the primary sintering time is 8 to 20 hours, for example, 8 hours, 10 hours, 15 hours, 18 hours or 20 hours.

[0023] In one embodiment, the primary sintering atmosphere includes nitrogen and / or oxygen.

[0024] In one embodiment, the temperature of the secondary sintering in step (2) is 800-1000°C, for example, 800°C, 850°C, 900°C, 950°C or 100°C.

[0025] In one embodiment, the secondary sintering time is 2 to 20 hours, for example, 2 hours, 8 hours, 15 hours, 18 hours or 20 hours.

[0026] In one embodiment, the atmosphere of the secondary sintering includes air and / or oxygen.

[0027] In one embodiment, the cooling rate in step (2) is less than 1.5°C / min.

[0028] In one embodiment, the insulation temperature is 500-600°C, for example, 50°C, 52°C, 55°C, 58°C or 60°C.

[0029] In one embodiment, the insulation time is 1 to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours.

[0030] At the holding temperature of the embodiment of the present disclosure, the surface Mn of the material 4+ Reduced to Mn 3+ , the lattice is distorted, forming the O'3 phase.

[0031] In one embodiment, the quenching method in step (2) includes taking out the material and placing it in liquid nitrogen or a closed inert atmosphere.

[0032] The quenching process described in the embodiment of the present disclosure can enable the O'3 phase formed at the holding temperature to exist stably at room temperature.

[0033] In a third aspect, an embodiment of the present disclosure provides a positive electrode plate, wherein the positive electrode plate comprises the sodium ion positive electrode material as described in the first aspect.

[0034] In a fourth aspect, an embodiment of the present disclosure provides a sodium ion battery, wherein the sodium ion battery comprises the positive electrode sheet as described in the third aspect.

[0035] Compared with the related art, the present disclosure has the following beneficial effects:

[0036] (1) During the preparation of the sodium ion positive electrode material disclosed in the present invention, +4 valent element doping is performed in advance. The doping of +4 metal elements improves the structural stability of the monoclinic O'3 phase and weakens the Jan-Taylor effect, thereby improving the capacity and cycle stability of the material. The single-fired material doped with the +4 valent element is mixed with a +2 valent metal source and sintered, and the O'3 phase is formed by surface doping with +2 metal elements and heat preservation in the cooling stage. The coexistence of O3-O'3 is maintained at room temperature by quenching in an extremely rapid cooling manner, and an O3-O'3 composite phase with a certain O'3 phase content is prepared. At the same time, due to the initial stable monoclinic O'3 phase, the O3 phase may be directionally induced to convert into a more stable O'3 phase during the charge and discharge process, so that the material as a whole has excellent capacity and cycle retention rate.

[0037] (2) The capacity retention rate of the battery made of the sodium ion positive electrode material disclosed in the present invention after 100 cycles of 1C can reach more than 89.1%.

[0038] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

[0040] FIG1 is a SEM image of the sodium ion positive electrode material prepared in Example 1 of the present disclosure.

[0041] FIG2 is an XRD diagram of the sodium ion positive electrode materials prepared in Examples 1-3 and Comparative Examples 1-4 of the present disclosure.

[0042] FIG3 is an XRD diagram of the sodium ion positive electrode materials prepared in Examples 1-3 and Comparative Examples 1-4 of the present disclosure. DETAILED DESCRIPTION

[0043] The technical solution of the present disclosure is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only used to help understand the present disclosure and should not be regarded as specific limitations of the present disclosure.

[0044] Example 1

[0045] This embodiment provides a sodium ion positive electrode material, and the preparation method of the sodium ion positive electrode material is as follows:

[0046] (1) nickel oxide, manganese oxide, iron oxide, titanium oxide and sodium carbonate were mixed in a molar ratio of Ni, Fe, Mn, Ti and Na of 0.25:0.15:0.57:0.03:0.98 (3% excess), sintered at 900° C. for 15 h and then pulverized to obtain a sintered material;

[0047] (2) The calcined material and 1% zinc oxide were mixed evenly, and sintered in an air atmosphere at a sintering temperature of 920°C, kept warm for 6 hours, and then cooled to 550°C at a cooling rate of 1°C / min and kept warm for 2 hours. After the insulation was completed, the material was immediately taken out and placed in liquid nitrogen. After the material was cooled, it was crushed and sieved to obtain the sodium ion positive electrode material. The SEM image of the sodium ion positive electrode material is shown in Figure 1.

[0048] Example 2

[0049] This embodiment provides a sodium ion positive electrode material, and the preparation method of the sodium ion positive electrode material is as follows:

[0050] (1) nickel oxide, manganese oxide, iron oxide, titanium oxide and sodium carbonate are mixed in a molar ratio of Ni, Fe, Mn, Ti and Na of 0.25:0.15:0.57:0.03:0.98, sintered at 900° C. for 15 h and then crushed to obtain a sintered material;

[0051] (2) The sintered material and 1% copper oxide were mixed evenly, and sintered in an air atmosphere at a sintering temperature of 920°C, kept warm for 6 hours, and then cooled to 550°C at a cooling rate of 1°C / min and kept warm for 2 hours. After the insulation was completed, the material was immediately taken out and placed in liquid nitrogen. After the material was cooled, it was crushed and sieved to obtain the sodium ion positive electrode material.

[0052] Example 3

[0053] This embodiment provides a sodium ion positive electrode material, and the preparation method of the sodium ion positive electrode material is as follows:

[0054] (1) nickel oxide, manganese oxide, iron oxide, zirconium oxide and sodium carbonate are mixed in a molar ratio of Ni, Fe, Mn, Ti and Na of 0.25:0.15:0.57:0.03:0.98, sintered at 900° C. for 15 h and then crushed to obtain a sintered material;

[0055] (2) The sintered material and 1% copper oxide were mixed evenly, and sintered in an air atmosphere at a sintering temperature of 920°C, kept warm for 6 hours, and then cooled to 550°C at a cooling rate of 1°C / min and kept warm for 2 hours. After the insulation was completed, the material was immediately taken out and placed in liquid nitrogen. After the material was cooled, it was crushed and sieved to obtain the sodium ion positive electrode material.

[0056] Example 4

[0057] The only difference between this embodiment and embodiment 1 is that the holding temperature is 450° C., and other conditions and parameters are exactly the same as those in embodiment 1.

[0058] Example 5

[0059] The only difference between this embodiment and embodiment 1 is that the holding temperature is 650° C., and other conditions and parameters are exactly the same as those in embodiment 1.

[0060] Example 6

[0061] The only difference between this embodiment and embodiment 1 is that the cooling rate is 2°C / min, and the other conditions and parameters are exactly the same as those in embodiment 1.

[0062] Comparative Example 1

[0063] This comparative example provides a sodium ion positive electrode material, and the preparation method of the sodium ion positive electrode material is as follows:

[0064] (1) nickel oxide, manganese trioxide, ferric oxide and sodium carbonate were mixed in a molar ratio of Ni, Fe, Mn, Ti and Na of 0.25:0.15:0.60:0.98 (3% excess), sintered at 900°C in an oxygen atmosphere for 15 hours and crushed to obtain a sintered material;

[0065] (2) The sintered material was sintered in an air atmosphere at a sintering temperature of 920° C. for 6 hours. After the material was naturally cooled, it was crushed and sieved to obtain the sodium ion positive electrode material.

[0066] Comparative Example 2

[0067] This comparative example provides a sodium ion positive electrode material, and the preparation method of the sodium ion positive electrode material is as follows:

[0068] (1) nickel oxide, manganese trioxide, ferric oxide and sodium carbonate were mixed in a molar ratio of Ni, Fe, Mn, Ti and Na of 0.25:0.15:0.60:0.98 (3% excess), sintered at 900°C in an oxygen atmosphere for 15 hours and crushed to obtain a sintered material;

[0069] (2) The sintered material was sintered in an air atmosphere at a sintering temperature of 920° C. for 6 hours, then cooled to 550° C. at a cooling rate of 1° C. / min and kept at that temperature for 2 hours. After the material was cooled, it was crushed and sieved to obtain the sodium ion positive electrode material.

[0070] Comparative Example 3

[0071] This comparative example provides a sodium ion positive electrode material, and the preparation method of the sodium ion positive electrode material is as follows:

[0072] (1) nickel oxide, manganese oxide, iron oxide, titanium oxide and sodium carbonate were mixed in a molar ratio of Ni, Fe, Mn, Ti and Na of 0.25:0.15:0.57:0.03:0.98 (3% excess), sintered at 900° C. in an oxygen atmosphere for 15 h and crushed to obtain a sintered material;

[0073] (2) The sintered material was sintered in an air atmosphere at a sintering temperature of 920° C. for 6 hours, then cooled to 550° C. at a cooling rate of 1° C. / min and kept at that temperature for 2 hours. After the material was cooled, it was crushed and sieved to obtain the sodium ion positive electrode material.

[0074] Comparative Example 4

[0075] This comparative example provides a sodium ion positive electrode material, and the preparation method of the sodium ion positive electrode material is as follows:

[0076] (1) nickel oxide, manganese trioxide, ferric oxide and sodium carbonate were mixed in a molar ratio of Ni, Fe, Mn and Na of 0.25:0.15:0.60:0.98, sintered at 900°C in an oxygen atmosphere for 15 hours and crushed to obtain a sintered material;

[0077] (2) Sintering the material in an air atmosphere at a sintering temperature of 920° C. for 6 hours. After cooling, the material is crushed and sieved to obtain the sodium ion positive electrode material.

[0078] Performance testing:

[0079] The positive electrode material prepared in the embodiment and the comparative example was mixed with a binder and conductive carbon black in a ratio of 90:5:5, NMP solvent was added and stirred, and the mixture was coated on a current collector, dried, and rolled to obtain a positive electrode sheet. The negative electrode was a sodium sheet. A battery was made and its cycle performance was tested at a test voltage of 1.5 to 4.2 V. The test results are shown in Table 1:

[0080] Table 1

[0081] As can be seen from Table 1, according to Examples 1-3, the capacity retention rate of the battery made of the sodium ion positive electrode material disclosed in the present invention after 100 cycles of 1C can reach more than 89.1%.

[0082] By comparing Example 1 with Examples 4-5, it can be seen that during the preparation process of the sodium ion positive electrode material described in the present disclosure, the insulation temperature affects its performance. When the insulation temperature is controlled at 500-600°C, the performance of the sodium ion positive electrode material obtained is better. If the insulation temperature is too low, the material structure is basically formed and it is difficult to generate the O'3 phase. If the insulation temperature is too high, the phase change temperature region cannot be reached and it is difficult to generate the O'3 phase.

[0083] By comparing Example 1 and Example 6, it can be seen that during the preparation process of the sodium ion positive electrode material described in the present disclosure, the cooling rate after insulation will affect its performance. The cooling rate is controlled below 1.5°C, and the performance of the sodium ion positive electrode material obtained is better. If the temperature is cooled too quickly, the material cannot be accurately cooled to a specific temperature for insulation, and the actual temperature deviates from the set temperature.

[0084] From the comparison between Example 1 and Comparative Examples 1-2, it can be seen that the preparation of O3-O'3 sodium ion positive electrode material described in the present disclosure is feasible, but the cycle performance of Comparative Example 2 is worse than that of Comparative Example 1, which may be due to the structural instability caused by the direct introduction of O'3.

[0085] From the comparison between Example 1 and Comparative Example 3, it can be seen that the cycle performance of O3-O'3 can be effectively improved by doping with +4-valent metal elements, indicating that doping can stabilize the structure of O3-O'3.

[0086] From the comparison between Example 1 and Comparative Example 4, it can be seen that coating with +2-valent metal elements can improve the cycle performance of O3-O'3 to a certain extent, but the effect is not as good as that of Comparative Example 3.

[0087] It can be seen from Examples 1-3 and Comparative Examples 2-4 that the O3-O'3 sodium ion positive electrode material prepared in the present disclosure and the introduction of +4 and +2 metal elements have a significant improvement on the material performance and is superior to the O3 phase material prepared by the conventional process in Comparative Example 1.

[0088] The XRD patterns of the sodium ion positive electrode materials obtained in Examples 1-3 and Comparative Examples 1-4 are shown in FIG2-3 . As can be seen from FIG2-3 , both Examples 1-3 and Comparative Example 2 successfully prepared materials having an O 3 -O' 3 composite phase.

Claims

1. A sodium ion positive electrode material, comprising an O3-type layered oxide and an O'3-type layered oxide, wherein the chemical formula of the sodium ion positive electrode material is O3-Na x Ni y Fe z Mn t M h Q n O2&O'3-Na a Ni b Fe c Mn e M f Q g O2, wherein 0.76≤(x+a)≤1.03, 0≤(y+b)≤1, 0≤(z+c)≤0.5, 0≤(t+e)≤1, 0.05≤(h+f)≤0.25, 0.005≤(n+g)≤0.1, M is a +2-valent metal element, and Q is a +4-valent metal element.

2. The sodium ion positive electrode material according to claim 1, wherein The M includes any one of Zn, Cu, Mg, Ca, Sr or Ba or a combination of at least two of them, preferably any one of Zn, Cu, Mg or Sr or a combination of at least two of them.

3. The sodium ion positive electrode material according to claim 1 or 2, wherein The Q includes Zr and / or Ti.

4. The sodium ion positive electrode material according to any one of claims 1 to 3, wherein The sodium ion positive electrode material is in layered form.

5. The sodium ion positive electrode material according to any one of claims 1 to 4, wherein Based on the mass of the sodium ion positive electrode material being 100%, the mass fraction of the O'3 type layered oxide is 0.1-10%.

6. A method for preparing the sodium ion positive electrode material according to any one of claims 1 to 5, the method comprising the following steps: (1) mixing oxides of Ni, Fe, Mn and Q with a sodium source and sintering them once to obtain a single-sintered material; (2) The primary sintered material and the oxide of M are mixed, and after secondary sintering, the temperature is lowered to a holding temperature for holding, and after the holding is completed, quenching is immediately performed to obtain the sodium ion positive electrode material.

7. The preparation method according to claim 6, wherein The primary sintering temperature in step (1) is 800-1000°C.

8. The preparation method according to claim 6 or 7, wherein: The time of the primary sintering is 8 to 20 hours.

9. The preparation method according to any one of claims 6 to 8, wherein: The primary sintering atmosphere includes nitrogen and / or oxygen.

10. The preparation method according to any one of claims 6 to 9, wherein: The temperature of the secondary sintering in step (2) is 800-1000°C.

11. The preparation method according to any one of claims 6 to 10, wherein: The secondary sintering time is 2 to 20 hours.

12. The preparation method according to any one of claims 6 to 11, wherein: The atmosphere of the secondary sintering includes air and / or oxygen.

13. The preparation method according to any one of claims 6 to 12, wherein: The cooling rate in step (2) is less than 1.5°C / min.

14. The preparation method according to any one of claims 6 to 13, wherein: The insulation temperature is 500-600°C.

15. The preparation method according to any one of claims 6 to 14, wherein: The insulation time is 1 to 3 hours.

16. The preparation method according to any one of claims 6 to 15, wherein: The quenching method in step (2) includes taking out the material and placing it in liquid nitrogen or a closed inert atmosphere.

17. A positive electrode plate, comprising the sodium ion positive electrode material according to any one of claims 1 to 5.

18. A sodium ion battery, comprising the positive electrode sheet according to claim 17.

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