A sodium-ion battery cathode material and its preparation method, and sodium-ion batteries

Abstract

This invention discloses a method for preparing a sodium-ion battery cathode material, comprising the following steps: Step S1, mixing and ball-milling a predetermined mass of precursor material, sodium carbonate, phosphorus source, and zirconium source to obtain a mixture, wherein the molar ratio of sodium to the metal element in the precursor is 0.5–2, and the amount of phosphorus and zirconium added is 0.05–2 wt% of the mixture; Step S2, sintering the mixture obtained in Step S1 in an oxygen-containing atmosphere, controlling the sintering temperature at 600℃–1000℃ and the sintering time at 0.5–16 h, to obtain the target sodium-ion battery cathode material, wherein the target sodium-ion battery cathode material is a Zr-doped NaZr2(PO4)3 coated Na... n Ni x Fe y Mn 1‑x‑y O2 cathode material. This invention aims to improve the electrochemical performance of cathode materials, thereby enhancing their specific capacity and cycle performance.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion batteries, and more particularly to a sodium-ion battery cathode material, its preparation method, and a sodium-ion battery. Background Technology

[0002] Currently, lithium-ion batteries are widely used in electric vehicles, mobile power supplies, and energy storage due to their high specific energy and environmental friendliness. However, with the development of 3C products, new energy vehicles, and energy storage industries, and the scarcity of lithium and cobalt resources, the development of lithium-ion batteries is limited. Sodium-ion batteries, however, offer similar performance to lithium-ion batteries, and sodium resources are abundant, low-cost, and non-toxic. Therefore, developing sodium-ion batteries is a cost-effective alternative to lithium-ion batteries. However, due to the large radius and slow diffusion rate of sodium ions, sodium-ion cathode materials still suffer from problems such as low specific capacity and poor cycle performance. Therefore, based on these issues, there is an urgent need to propose a new preparation process for sodium-ion cathode materials to address these shortcomings. Summary of the Invention

[0003] The main objective of this invention is to provide a sodium-ion battery cathode material, its preparation method, and a sodium-ion battery, aiming to solve the technical problems of low specific capacity and poor cycle performance of existing sodium-ion cathode materials.

[0004] To achieve the above objectives, the present invention provides a method for preparing a sodium-ion battery cathode material, the method comprising the following steps:

[0005] Step S1: Mix the precursor material, sodium carbonate, phosphorus source, and zirconium source of a predetermined mass and ball mill them to obtain a mixture. The molar ratio of sodium to the metal element in the precursor is 0.5–2, and the amounts of phosphorus and zirconium added are 0.05–2 wt% of the mixture. The precursor material has the chemical formula Ni. x Fe y Mn 1-x-y (OH)2, 0 <x<1,0<y<1,0<1-x-y<1;

[0006] Step S2: The mixture obtained in step S1 is sintered in an oxygen-containing atmosphere, with the sintering temperature controlled at 600℃-1000℃ and the sintering time at 0.5-16h, to obtain the target sodium-ion battery cathode material. The target sodium-ion battery cathode material is a Zr-doped NaZr2(PO4)3 coated Na... n Ni x Fe y Mn 1-x-y O2 cathode material, 0.5 <n<2.0。

[0007] Optionally, the milling medium in step S1 is a zirconia ball with a diameter of 0.5-1.5 cm.

[0008] Optionally, in step S1, the ball-to-material mass ratio in the ball milling process is 0.2-2, the ball milling rate is 100-300 rpm / min, and the ball milling time is 0.5-2 h.

[0009] Optionally, the precursor material is Ni. 0.33 Fe 0.33 Mn 0.34 (OH)2 or Ni 0.4 Fe 0.2 Mn 0.4 (OH)2.

[0010] Optionally, the phosphorus source includes at least one of diammonium hydrogen phosphate, ammonium dihydrogen phosphate, potassium dihydrogen phosphate, sodium phosphate, and sodium dihydrogen phosphate.

[0011] Optionally, the zirconium source includes at least one of zirconium oxide, zirconium carbonate, zirconium hydroxide, zirconium oxychloride, zirconium chloride, and zirconium nitrate.

[0012] Optionally, in step S2, the mixture obtained in step S1 is placed in an atmosphere furnace for sintering, and oxygen is introduced. The temperature in the atmosphere furnace is controlled to rise to 700°C, 800°C or 900°C and held for 10-16 hours. After natural cooling, the target sodium-ion battery cathode material is obtained.

[0013] Optionally, the method further includes: crushing and sieving the target sodium-ion battery cathode material.

[0014] In addition, to achieve the above objectives, the present invention also provides a sodium-ion battery cathode material, wherein the cathode material is prepared according to the preparation method of sodium-ion battery cathode material described in any one of the above claims.

[0015] In addition, to achieve the above objectives, the present invention also provides a sodium-ion battery, which includes a positive electrode, a negative electrode, a separator, and an electrolyte. The separator is used to separate the positive electrode and the negative electrode, and the active material of the positive electrode is the above-mentioned sodium-ion battery positive electrode material.

[0016] Beneficial effects:

[0017] (1) The sodium-ion battery cathode material of the present invention is prepared by mixing and ball milling a precursor material, sodium carbonate, phosphorus source and zirconium source, and sintering in an oxidizing atmosphere, thereby obtaining Zr-doped and NaZr2(PO4)3-coated Na in a one-step process. n Ni x Fe y Mn 1-x-y O2 cathode material.

[0018] (2) The sodium-ion battery cathode material obtained is a single crystal morphology, and the NaZr2(PO4)3 coated on the surface can act as a barrier to prevent side reactions between the material and the electrolyte, thereby reducing the occurrence of side reactions of the cathode material. Furthermore, Zr doping can also improve the structural stability of the cathode material during application.

[0019] (3) The generated NaZr2(PO4)3 coating layer can also react with the residual alkali on the surface of the cathode material, thereby reducing the residual alkali in the material and reducing the harm of residual alkali to the material. In addition, NaZr2(PO4)3 has excellent sodium ion rapid conduction ability, which can provide a channel for sodium ion diffusion, improve the electrochemical performance of the material, and based on the combined effect of coating and doping in the cathode material, it can protect the surface and bulk structure of the material, delay the degradation of the surface and bulk structure, improve the performance of the material, and thus make the cathode material have a stable surface morphology and bulk structure.

[0020] (4) When the cathode material is used in sodium-ion batteries, the specific capacity can reach 119.1 mAh / g at room temperature 2.0-4.0V 1C discharge. After 100 cycles of 1C, the material capacity retention rate is 95.9%, and the specific capacity and cycle performance are significantly improved. Attached Figure Description

[0021] Figure 1 This is a schematic flowchart of an embodiment of a method for preparing a sodium-ion battery cathode material according to the present invention;

[0022] Figure 2 This is a SEM image of the sodium-ion battery cathode material in Example 1 of this invention;

[0023] Figure 3 This is a SEM image of the sodium-ion battery cathode material in Example 2 of the present invention;

[0024] Figure 4 This is a SEM image of the sodium-ion battery cathode material in Example 3 of the present invention;

[0025] Figure 5 This is a SEM image of the sodium-ion battery cathode material in Example 4 of the present invention.

[0026] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0027] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0028] See Figure 1, A schematic flow chart of an embodiment of a method for preparing a positive electrode material of a sodium-ion battery is provided by the present invention. The method includes the following steps:

[0029] Step S1, mixing a preset mass of precursor materials, sodium carbonate, a phosphorus source, and a zirconium source and performing ball milling treatment to obtain a mixed material.

[0030] Specifically, the chemical formula of the precursor material is Ni x Fe y Mn 1-x-y (OH)2, where 0 < x < 1, 0 < y < 1, 0 < 1 - x - y < 1, and the molar ratio of sodium element to metal elements in the precursor is 0.5 - 2. The addition amounts of phosphorus element and zirconium element are 0.05 - 2 wt% of the mixed material. The phosphorus source includes at least one of diammonium hydrogen phosphate, ammonium dihydrogen phosphate, potassium dihydrogen phosphate, sodium phosphate, and sodium dihydrogen phosphate. The zirconium source includes at least one of zirconium oxide, zirconium carbonate, zirconium hydroxide, zirconium oxychloride, zirconium chloride, and zirconium nitrate.

[0031] Further, the ball milling medium in the ball milling treatment is zirconia balls. The mass of the zirconia balls is 0.5 - 1.5 cm in diameter. Different diameter ratios of zirconia balls can be selected according to the specific material usage. And the mass ratio of balls to materials in the ball milling treatment is 0.2 - 2, the ball milling rate is 100 - 300 rpm / min, and the ball milling time is 0.5 - 2 h.

[0032] Step S2, sintering the mixed material obtained in step S1 in an oxygen-containing atmosphere, controlling the sintering temperature to be 600°C - 1000°C, and the sintering time to be 0.5 - 16 h to obtain the target positive electrode material of a sodium-ion battery. Specifically, the mixed material obtained in step S1 is put into an atmosphere furnace for sintering, and oxygen is introduced. The temperature in the atmosphere furnace is controlled to rise to 600°C - 1000°C and kept for 0.5 - 16 h. After natural cooling, the target positive electrode material of a sodium-ion battery is obtained.

[0033] Further, the target positive electrode material of a sodium-ion battery needs to be crushed and sieved to meet the particle size requirements of a sodium-ion battery. It can be seen that the positive electrode material of a sodium-ion battery prepared by the present invention is obtained by mixing a precursor material, sodium carbonate, a phosphorus source, and a zirconium source, performing ball milling, sintering in an oxidizing atmosphere, and adopting a one-step method to obtain a Na n Ni x Fe y Mn 1-x-y O2 positive electrode material, 0.5 < n < 2.0.

[0034] Further, in order to better illustrate the specific performance of the positive electrode material of a sodium-ion battery prepared by the present invention, the following will be described in detail through specific examples

[0035] Example 1

[0036] Take 200g of Ni 0.33 Fe 0.33 Mn 0.34 (OH)2, 80.2 g of Na2CO3, 3.42 g of (NH4)2HPO4, 2.91 g of ZrO2, and 300 g of zirconia balls were added to a ball mill jar, with the diameter of the zirconia balls controlled between 0.5 and 1.5 cm. The mixture was stirred at 200 rpm / min for 1 hour to obtain a final mixture. This mixture was then placed in an atmosphere furnace for sintering, oxygen was introduced, and the temperature was raised to 800 °C and held for 10 hours. After natural cooling, NaZr2(PO4)3 coated with Zr-doped NaNi was obtained. 0.33 Fe 0.33 Mn 0.34 O2 material was then crushed and sieved. The resulting sodium-ion battery cathode material was then subjected to SEM analysis, specifically as follows: Figure 2 As shown in the figure, the cathode material exhibits good microstructure and a high degree of single crystallization.

[0037] Example 2

[0038] Take 200g of Ni 0.33 Fe 0.33 Mn 0.34 120.2 g of (OH)2, 6.13 g of Na2CO3, 6.34 g of NH4H2PO4, 6.34 g of Zr(CO3)2, and 180 g of zirconia balls were added to a ball mill jar, with the diameter of the zirconia balls controlled between 0.5 and 1.5 cm. The mixture was stirred at 150 rpm / min for 2 hours to obtain a final mixture. This mixture was then placed in an atmosphere furnace for sintering, oxygen was introduced, and the temperature was raised to 900 °C and held for 12 hours. After natural cooling, NaZr2(PO4)3 coated with Zr-doped NaNi was obtained. 0.33 Fe 0.33 Mn 0.34 O2 material was then crushed and sieved. The resulting sodium-ion battery cathode material was then subjected to SEM analysis, specifically as follows: Figure 3 As shown in the figure, the cathode material exhibits good microstructure and a high degree of single crystallization.

[0039] Example 3

[0040] Take 200g of Ni 0.33 Fe 0.33 Mn 0.3465.32 g of (OH)2, 8.19 g of Na2CO3, 3.56 g of Na3PO4, 3.56 g of ZrOCl2·8H2O, and 320 g of zirconia balls were added to a ball mill jar, with the diameter of the zirconia balls controlled between 0.5 and 1.5 cm. The mixture was stirred at 280 rpm / min for 1.2 h to obtain a mixture, which was then placed in an atmosphere furnace for sintering. Oxygen was introduced, and the temperature was raised to 700 °C and held for 16 h. After natural cooling, NaNi doped with Zr and coated with NaZr2(PO4)3 was obtained. 0.33 Fe 0.33 Mn 0.34 O2 material was then crushed and sieved. The resulting sodium-ion battery cathode material was then subjected to SEM analysis, specifically as follows: Figure 4 As shown in the figure, the cathode material exhibits good microstructure and a high degree of single crystallization.

[0041] Example 4

[0042] Take 200g of Ni 0.4 Fe 0.2 Mn 0.4 74.2 g of (OH)2, 3.3 g of Na2CO3, 1.8 g of NH4H2PO4, 1.8 g of ZrO2, and 350 g of zirconia balls were added to a ball mill jar, with the diameter of the zirconia balls controlled between 0.5 and 1.5 cm. The mixture was stirred at 240 rpm / min for 1.5 h to obtain a final mixture. This mixture was then placed in an atmosphere furnace for sintering, oxygen was introduced, and the temperature was raised to 760 °C and held for 12 h. After natural cooling, Zr-doped NaNi coated with NaZr2(PO4)3 was obtained. 0.4 Fe 0.2 Mn 0.4 O2 material was then crushed and sieved. The resulting sodium-ion battery cathode material was then subjected to SEM analysis, specifically as follows: Figure 5 As shown in the figure, the cathode material exhibits good microstructure and a high degree of single crystallization.

[0043] Comparative Example 1

[0044] Take 200g of Ni 0.33 Fe 0.33 Mn 0.34 (OH)2, 80.2 g of Na2CO3, and 280 g of zirconia balls were added to a ball mill jar and mixed at 200 rpm / min for 1 h to obtain a mixture. This mixture was then placed in an atmosphere furnace for sintering, with oxygen introduced and the temperature raised to 800 °C and held for 10 h. After natural cooling, NaNi was obtained. 0.33 Fe 0.33 Mn 0.34 O2 material is then crushed and sieved.

[0045] Comparative Example 2

[0046] Take 200g of Ni 0.33 Fe 0.33 Mn 0.34 (OH)2, 80.2g Na2CO3, 1.45g ZrO2, and 280g zirconia balls were added to a ball mill jar and mixed at 200 rpm / min for 1 hour. The mixed material 1 was then placed in an atmosphere furnace for sintering, oxygen was introduced, and the temperature was raised to 800℃ and held for 10 hours. The sintered material was crushed and sieved. 100g of the treated material was taken and put into a ball mill jar together with 3.62g NaZr2(PO4)3 and 105g zirconia balls were added. The mixture was then mixed at 200 rpm / min for 1 hour.

[0047] The mixed material 2 was placed in an atmosphere furnace for sintering, oxygen was introduced, and the temperature was raised to 600℃ and held for 6 hours; after natural cooling, NaZr2(PO4)3 coated with Zr-doped NaNi was obtained. 0.33 Fe 0.33 Mn 0.34 O2 material is then crushed and sieved.

[0048] Comparative Example 3:

[0049] Take 200g of Ni 0.33 Fe 0.33 Mn 0.34 (OH)2, 80.2 g of Na2CO3, 1.45 g of ZrO2, and 280 g of zirconia balls were added to a ball mill jar and mixed at 200 rpm / min for 1 h. The mixture was then placed in an atmosphere furnace for sintering, oxygen was introduced, and the temperature was raised to 800 °C and held for 10 h. After natural cooling, Zr-doped NaNi was obtained. 0.33 Fe 0.33 Mn 0.34 O2 material is then crushed and sieved.

[0050] Comparative Example 4:

[0051] Take 200g of Ni 0.33 Fe 0.33 Mn 0.34 (OH)2, 80.2g Na2CO3, and 280g zirconia balls were added to a ball mill jar and mixed at 200 rpm / min for 1 hour. The mixed material 1 was then placed in an atmosphere furnace for sintering, oxygen was introduced, and the temperature was raised to 800℃ and held for 10 hours. The sintered material was crushed and sieved. 100g of the sintered material was taken and placed together with 3.62g NaZr2(PO4)3 into a ball mill jar, and 105g zirconia balls were added. The mixture was then mixed at 200 rpm / min for 1 hour.

[0052] The mixed material 2 was placed in an atmosphere furnace for sintering, oxygen was introduced, and the temperature was raised to 600℃ and held for 6 hours; after natural cooling, NaZr2(PO4)3-coated NaNi was obtained. 0.33 Fe 0.33 Mn 0.34 O2 material is then crushed and sieved.

[0053] Furthermore, the surface residual alkali of the positive electrode materials in Examples 1-4 and Comparative Examples 1-4 was subjected to appropriate OH treatment. - CO3 2- The mass percentage was determined, and as shown in Table 1, the OH content in Examples 1-4... - CO3 2- The mass percentages of OH in all samples were lower than those in Comparative Examples 1-4. - CO3 2- As can be seen from the mass percentage, the residual alkali in the positive electrode materials prepared in Examples 1-4 with NaZr2(PO4)3 coating on the surface is reduced to a certain extent, which shows that NaZr2(PO4)3 can react with the residual alkali on the material surface and reduce the harm of residual alkali to the material.

[0054] Table 1 - OH- OH- ions in sodium-ion battery cathode materials of the Examples and Comparative Examples - CO3 2- Quality percentage

[0055] sample <![CDATA[OH - / wt.%]]> <![CDATA[CO3 2- / wt.%]]> Example 1 5.925 1.987 Example 2 5.884 1.995 Example 3 5.838 1.986 Example 4 5.745 1.903 Comparative Example 1 6.244 2.237 Comparative Example 2 6.081 2.149 Comparative Example 3 6.255 2.247 Comparative Example 4 6.077 2.089

[0056] Furthermore, sodium-ion batteries were fabricated using the positive electrode materials from Examples 1-4 and Comparative Examples 1-4. Each sodium-ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The separator separates the positive and negative electrode. The active material of the positive electrode is the same as that used in Examples 1-4 and Comparative Examples 1-4. The electrochemical performance of the sodium-ion batteries fabricated with different positive electrode materials was measured, as shown in Table 2. The Zr-doped and NaZr2(PO4)3-coated positive electrode exhibited a higher discharge capacity and slower decay rate than the untreated material. This indicates that Zr doping and NaZr2(PO4)3 coating can improve the material's capacity and prevent electrolyte erosion, thus improving cycle performance. Furthermore, the positive electrode materials with Zr doping and NaZr2(PO4)3 coating prepared by the one-step method in Examples 1-4 showed superior electrochemical performance compared to the separately doped and coated positive electrode materials. This verifies that the positive electrode material prepared by the one-step method in this invention has a more stable structure.

[0057] Table 2 - Electrochemical performance of batteries made from the cathode materials prepared in the Examples and Comparative Examples

[0058]

[0059] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or system. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or system that includes that element.

[0060] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0061] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A method for preparing a sodium-ion battery cathode material, characterized in that, The method includes the following steps: Step S1, mix a precursor material of a preset quality, sodium carbonate, a phosphorus source, and a zirconium source and perform ball milling treatment to obtain a mixed material. Among them, the molar ratio of sodium element to the metal element in the precursor is 0.5-2, and the addition amounts of phosphorus element and zirconium element are 0.05-2 wt% of the mixed material. The chemical formula of the precursor material is Ni x Fe y Mn 1-x-y (OH)2, where 0<x<1, 0<y<1, 0<1-x-y<1, the ball milling rate is 100-300 rpm / min, the ball milling time is 0.5-2 h. The phosphorus source includes at least one of diammonium hydrogen phosphate, ammonium dihydrogen phosphate, potassium dihydrogen phosphate, sodium phosphate, and sodium dihydrogen phosphate. The zirconium source includes at least one of zirconium oxide, zirconium carbonate, zirconium hydroxide, zirconium oxychloride, zirconium chloride, and zirconium nitrate; Step S2: The mixture obtained in step S1 is sintered in an oxygen-containing atmosphere, with the sintering temperature controlled at 600℃-1000℃ and the sintering time at 0.5-16h, to obtain the target sodium-ion battery cathode material. The target sodium-ion battery cathode material is a Zr-doped NaZr2(PO4)3 coated Na... n Ni x Fe y Mn 1-x-y O2 cathode material, 0.5 <n<2.0。 2. The method for preparing the sodium-ion battery cathode material according to claim 1, characterized in that, The milling medium in step S1 is zirconia balls with a diameter of 0.5-1.5 cm.

3. The method for preparing the sodium-ion battery cathode material according to claim 2, characterized in that, The ball-to-material mass ratio in the ball milling process in step S1 is 0.2-2.

4. The method for preparing the sodium-ion battery cathode material according to any one of claims 1 to 3, characterized in that, The precursor material is Ni. 0.33 Fe 0.33 Mn 0.34 (OH)2 or Ni 0.4 Fe 0.2 Mn 0.4 (OH)2.

5. The method for preparing the sodium-ion battery cathode material according to claim 4, characterized in that, In step S2, the mixture obtained in step S1 is placed in an atmosphere furnace for sintering, and oxygen is introduced. The temperature in the atmosphere furnace is controlled to rise to 700-900℃ and held for 10-16 hours. After natural cooling, the target sodium-ion battery cathode material is obtained.

6. The method for preparing the sodium-ion battery cathode material according to claim 5, characterized in that, The method further includes: crushing and sieving the target sodium-ion battery cathode material.

7. A sodium-ion battery cathode material, characterized in that, The cathode material is prepared by the method for preparing sodium-ion battery cathode materials according to any one of claims 1 to 6.

8. A sodium-ion battery, characterized in that, The sodium-ion battery includes the sodium-ion battery cathode material as described in claim 7.

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