A high-capacity long-cycle sodium-ion battery positive electrode material and a preparation method and application thereof

Abstract

The application relates to a high-capacity long-circulation sodium ion battery positive electrode material and a preparation method and application thereof, the preparation method comprising the following steps: mixing a first precursor Me x Mn y (OH)2, x+y=1, 0.7 a Mn b (OH)2, a+b=1, 0.55

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a high-capacity, long-cycle sodium ion battery cathode material, a preparation method thereof, and applications thereof. Background Art

[0002] Sodium-ion batteries have emerged as an alternative energy storage battery in recent years, potentially replacing lithium-ion batteries in large-scale energy storage and low-speed electric vehicles. Their operating principles are similar to those of lithium-ion batteries, and sodium resources are widely available and abundant, while being more stable and affordable than lithium resources, potentially alleviating the problem of limited lithium resources.

[0003] Among the components of a battery, the performance of the cathode material often directly determines the ultimate performance of the finished battery. Therefore, the development of low-cost, high-capacity, and well-processed cathode materials for sodium-ion batteries is crucial for their practical application. Currently, the main types of cathode materials for sodium-ion batteries include transition metal layered oxides, polyanionic compounds, and Prussian blue compounds. Layered metal oxides, with their high reversible specific capacity, excellent electrochemical activity, and production processes largely consistent with those for lithium-ion battery cathode materials, are considered the most promising cathode materials for sodium-ion batteries for large-scale industrialization.

[0004] The main advantage of sodium-ion batteries over lithium-ion batteries lies in cost. In addition to considering the cost difference between lithium and sodium themselves, the cost of transition metal elements in layered positive electrode materials also accounts for a considerable proportion. Commonly used transition metal elements include Ni, Fe, Co, Mn, Cu, Zn, Cr, Ti, V, Zr, etc. Among them, Mn has been confirmed to be used in sodium-based positive electrode materials due to its low cost, abundant resources and favorable effect on the stability of the material structure. At the same time, in order to meet the needs of sodium-ion batteries in the fields of energy storage and low-speed electric vehicles, there are certain requirements for the capacity and cycle life of the positive electrode materials.

[0005] CN117285087A discloses a layered oxide, a preparation method thereof, and a sodium battery. The preparation method comprises: sintering a mixture containing a sodium source and a precursor to obtain the layered oxide; wherein the precursor comprises a first precursor and a second precursor. By adopting precursors of different particle sizes and regulating the relationship between particle size and mass, the tap density, compaction density, and rate performance are improved. However, it does not focus on improving the cycle performance of the battery.

[0006] CN115995533A discloses a layered composite oxide for sodium ion batteries. The preparation method is as follows: sodium oxalate, a cobalt source, an M source (at least one of Ti, Nb, Cu, Ni, V, and Cr), and an iron source are mixed, ball-milled, tableted, calcined, and ground to obtain a calcined powder; an isopropyl alcohol solution and the calcined powder are stirred to obtain a reaction precursor; and the reaction precursor is calcined to obtain the layered composite oxide. Although this preparation process uses doping elements to improve rate performance and cycle performance to a certain extent, its preparation process is complex and tedious, with a long cycle time, and this mixing method cannot ensure that the Na element is evenly dispersed within the layered composite oxide.

[0007] Therefore, how to provide a simple and effective preparation process to make the Na element evenly distributed inside the positive electrode material, thereby improving the capacity and cycle performance of layered sodium battery positive electrode materials, has become a technical problem that needs to be solved urgently. Summary of the Invention

[0008] To solve the above technical problems, the present invention provides a high-capacity, long-cycle sodium-ion battery cathode material, a preparation method, and an application thereof. A composite high-Mn element precursor is used to reduce the use of transition precious metals and reduce costs. At the same time, the presence of the Mn element can not only stabilize the material structure, but some low-priced Mn can also participate in the redox reaction, contributing to the capacity of the cathode material. The two-mixing and two-sintering processes are used to make the Na element more evenly enter the bulk phase of the cathode material, and the cathode material is composed of secondary particles formed by uniform agglomeration of primary particles, with higher capacity and excellent long-cycle performance.

[0009] To achieve this object, the present invention adopts the following technical solutions:

[0010] In a first aspect, the present invention provides a method for preparing a high-capacity, long-cycle sodium ion battery cathode material, the preparation method comprising the following steps:

[0011] (1) uniformly mixing a first precursor and a sodium source to obtain a first mixed sample, and performing a sintering operation to obtain a first sintered sample;

[0012] (2) uniformly mixing the second precursor, the additive, and the first sintered sample of step (1) to obtain a second mixed sample, and performing secondary sintering to obtain a high-capacity, long-cycle sodium ion battery cathode material;

[0013] Wherein, the chemical formula of the first precursor is Me x Mn y (OH)2, x+y=1, 0.7 <y<0.8,例如y可以是0.71、0.72、0.73、0.74、0.75、0.76、0.77、0.78或0.79等;所述第二前驱体的化学通式为Mea Mn b (OH)2, a+b=1, 0.55 <b<0.65,例如b可以是0.56、0.57、0.58、0.59、0.60、0.61、0.62、0.63或0.64等;所述第一前驱体的中值粒径大于所述第二前驱体的中值粒径;所述Me包括Ni、Co、Al、Fe、Cu、Zr或Mg中的任意一种或至少两种的组合。

[0014] The present invention adopts two mixing and two sintering processes. The two sintering processes are coordinated to prepare a high-capacity long-cycle sodium ion battery positive electrode material with a more uniform distribution of Na elements. Since the particle size of the first precursor is large, the path for Na ions to diffuse into the bulk phase is longer, so the sodium source and the first precursor are first sintered once, the first precursor and the sodium source are partially compounded, and the Na ions in part of the sodium source first diffuse into the first precursor bulk phase, and the remaining sodium source is uniformly retained on the surface of the first precursor, and then the second precursor is added. After the second sintering, the Na ions in the sodium source remaining on the surface of the first precursor diffuse into the bulk phase of the second precursor, and also continue to diffuse into the bulk phase of the first precursor, thereby making the Na element distribution in the prepared positive electrode material more uniform, and the high-capacity long-cycle sodium ion battery positive electrode material obtained by the preparation method is formed by uniform primary particle agglomeration of secondary particles, with higher capacity and better long-cycle performance.

[0015] The present invention adopts a composite high-Mn element precursor to reduce the use of transition noble metals and lower the cost. At the same time, the presence of the Mn element can not only stabilize the material structure, but some low-priced Mn can also participate in the redox reaction, contributing to the capacity of the positive electrode material. The two-time mixing and two-time sintering process can make the Na element more uniformly enter the bulk phase of the positive electrode material, and the secondary particles formed by the uniform agglomeration of primary particles of the positive electrode material have higher capacity and excellent long-cycle performance.

[0016] The high capacity means that the 0.1C discharge specific capacity of the prepared sodium ion battery positive electrode material is above 134.90 mAh / g.

[0017] The long cycle means that the capacity retention rate of the prepared sodium ion battery after 100 cycles at 1C is above 92.02%, and the capacity retention rate after 200 cycles at 1C is above 87.00%.

[0018] As a preferred technical solution of the present invention, the specific surface area of ​​the first precursor is 35 to 40 m 2 / g, for example 35m 2 / g、36m 2 / g、37m 2 / g、38m2 / g、39m 2 / g or 40m 2 / g, etc.

[0019] Preferably, the median particle size D50 of the first precursor is 8 to 10 μm, for example, 8 μm, 8.5 μm, 9 μm, 9.5 μm or 10 μm.

[0020] As a preferred technical solution of the present invention, the sodium source in step (1) includes any one of sodium carbonate, sodium bicarbonate, sodium hydroxide or sodium oxalate, or a combination of at least two thereof.

[0021] Preferably, in step (1), the molar ratio of Na in the sodium source to the overall metal elements in the first precursor is (1.2-1.6):1, for example, 1.2:1, 1.3:1, 1.4:1, 1.5:1 or 1.6:1, etc.

[0022] In the present invention, the molar ratio of Na in the sodium source to the overall metal element in the first precursor is controlled to partially recombine the first precursor and the sodium source, and then combined with a subsequent sintering process to make the Na element more evenly distributed in the positive electrode material. If the molar ratio is too small, that is, the content of the Na element is too low, it will affect the capacity of the positive electrode material, resulting in a reduction in capacity; if the molar ratio is too large, that is, the content of the Na element is too high, the prepared positive electrode material will cause homogenization and gelation during the preparation of the positive electrode slurry, affecting the preparation of the positive electrode sheet.

[0023] Preferably, the mixing method in step (1) includes mechanical mixing.

[0024] Preferably, the mechanical mixing comprises ball milling.

[0025] As a preferred technical solution of the present invention, the sintering atmosphere of the primary sintering in step (1) includes air or oxygen.

[0026] Preferably, the sintering temperature of the primary sintering is 600-800°C, for example, 600°C, 650°C, 700°C, 750°C or 800°C.

[0027] In the present invention, it is necessary to ensure that the temperature of the first sintering is lower than that of the second sintering. The purpose of the first sintering is to compound part of the sodium source with the first precursor. If the temperature of the first sintering is too high, the melting rate of the raw material and the decomposition rate of the precursor will be accelerated, making it difficult to fully mix, tending to grow directly, and wasting energy; if the temperature of the first sintering is too low, the raw material is difficult to melt and the precursor is incompletely decomposed, affecting the electrochemical properties of the prepared positive electrode material.

[0028] Preferably, the holding time of the primary sintering is 2 to 8 hours, for example, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours or 8 hours.

[0029] Preferably, the sintering pressure of the primary sintering is -20 to -30 Pa, such as -20 Pa, -22 Pa, -25 Pa, -28 Pa or -30 Pa.

[0030] As a preferred technical solution of the present invention, the specific surface area of ​​the second precursor is 15 to 20 m 2 / g, for example 15m 2 / g、16m 2 / g、17m 2 / g、18m 2 / g、19m 2 / g or 20m 2 / g, etc.

[0031] Preferably, the median particle size D50 of the second precursor is 4 to 6 μm, for example, 4 μm, 4.5 μm, 5 μm, 5.5 μm or 6 μm.

[0032] Preferably, based on the mass of the first precursor in step (1), the amount of the second precursor added is 20 to 40 wt%, for example, 20 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, 30 wt%, 32 wt%, 34 wt%, 36 wt%, 38 wt% or 40 wt%, etc.

[0033] As a preferred technical solution of the present invention, the additive in step (2) includes any one of Al2O3, ZrO4, TiO2, MgO or Nb2O5, or a combination of at least two of them.

[0034] Preferably, based on the mass of the first precursor in step (1), the amount of the additive added is 0.005-0.1wt%, for example, 0.005wt%, 0.008wt%, 0.01wt%, 0.03wt%, 0.05wt%, 0.08wt% or 0.1wt%, etc.

[0035] Preferably, the mixing method in step (2) includes mechanical mixing.

[0036] Preferably, the mechanical mixing comprises ball milling.

[0037] As a preferred technical solution of the present invention, the sintering atmosphere for the secondary sintering in step (2) includes air or oxygen.

[0038] Preferably, the sintering temperature of the secondary sintering is 850-1100°C, for example, 850°C, 880°C, 900°C, 920°C, 950°C, 980°C, 1000°C, 1020°C, 1050°C, 1080°C or 1100°C.

[0039] Preferably, the holding time of the secondary sintering is 10 to 20 hours, for example, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours or 20 hours.

[0040] Preferably, the sintering pressure of the secondary sintering is -20 to -30 Pa, such as -20 Pa, -22 Pa, -25 Pa, -28 Pa or -30 Pa.

[0041] Preferably, after the secondary sintering, the process further includes crushing, grinding and screening to remove iron.

[0042] As a preferred technical solution of the present invention, the preparation method comprises the following steps:

[0043] (1) The specific surface area is 35 to 40 m 2 / g, a first precursor with a D50 of 8 to 10 μm and a sodium source are uniformly mixed to obtain a first mixed sample, and the mixed sample is sintered once at 600 to 800°C and -20 to -30 Pa for 2 to 8 hours to obtain a first sintered sample;

[0044] Wherein, the chemical formula of the first precursor is Me x Mn y (OH)2, x+y=1, 0.7 <y<0.8;所述Me x Mn y Me in (OH)2 includes any one of Ni, Co, Al, Fe, Cu, Zr or Mg or a combination of at least two thereof; the sodium source includes any one of sodium carbonate, sodium bicarbonate, sodium hydroxide or sodium oxalate or a combination of at least two thereof; the molar ratio of Na in the sodium source to the overall metal elements in the first precursor is (1.2-1.6):1; the mixing method includes mechanical mixing; the mechanical mixing includes ball milling; the sintering atmosphere of the primary sintering includes air or oxygen;

[0045] (2) The specific surface area is 15 to 20 m 2 / g, a second precursor with a D50 of 4 to 6 μm, an additive, and the first sintered sample of step (1) are uniformly mixed to obtain a second mixed sample, which is then subjected to secondary sintering at 850 to 1100°C and -20 to -30 Pa, and kept warm for 10 to 20 hours. The high-capacity and long-cycle sodium ion battery positive electrode material is obtained by crushing, grinding, and screening to remove iron;

[0046] Wherein, the chemical formula of the second precursor is Me a Mn b (OH)2, a+b=1, 0.55 <b<0.65;所述Me a Mn bMe in (OH)2 includes any one of Ni, Co, Al, Fe, Cu, Zr or Mg, or a combination of at least two of them; based on the mass of the first precursor in step (1), the amount of the second precursor added is 20 to 40 wt%; the additive includes any one of Al2O3, ZrO4, TiO2, MgO or Nb2O5, or a combination of at least two of them; based on the mass of the first precursor in step (1), the amount of the additive added is 0.005 to 0.1 wt%; the mixing method includes mechanical mixing; the mechanical mixing includes ball milling; the sintering atmosphere of the secondary sintering includes air or oxygen.

[0047] In the second aspect, the present invention also provides a high-capacity, long-cycle sodium-ion battery positive electrode material, which is prepared by the preparation method described in the first aspect, and the high-capacity, long-cycle sodium-ion battery positive electrode material is a secondary particle formed by agglomeration of primary particles.

[0048] In a third aspect, the present invention further provides a sodium ion battery, comprising the high-capacity, long-cycle sodium ion battery positive electrode material described in the second aspect.

[0049] Compared with the prior art, the present invention has at least the following beneficial effects:

[0050] 1) The present invention uses a composite high-Mn element precursor to reduce the use of transition noble metals and lower costs. At the same time, the presence of the Mn element not only stabilizes the material structure, but also some low-cost Mn can participate in the redox reaction, contributing to the capacity of the positive electrode material.

[0051] 2) The present invention adopts a double mixing and double sintering process to make the Na element more evenly distributed in the bulk of the positive electrode material. The positive electrode material is formed by the secondary particles formed by the uniform agglomeration of primary particles, which has higher capacity and better long-cycle performance.

[0052] 3) The preparation method provided by the present invention is simple in process, easy to operate, and can be used for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a scanning electron microscope image of the high-capacity, long-cycle sodium-ion battery positive electrode material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0054] The technical solution of the present invention will be further described below with reference to the accompanying drawings and through specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention shall be subject to the claims.

[0055] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0056] Example 1

[0057] This embodiment provides a method for preparing a high-capacity, long-cycle sodium-ion battery cathode material, the preparation method comprising the following steps:

[0058] (1) According to the Na and Ni in sodium carbonate 0.15 Co 0.1 Mn 0.75 The molar ratio of the metal elements in (OH)2 is 1.4. Sodium carbonate and a specific surface area of ​​38m 2 / g, D50 is 9μm Ni 0.15 Co 0.1 Mn 0.75 (OH)2, the above raw materials were mixed with a high-speed mixer to obtain a first mixed sample, and sintered at 700 ° C for 5 h in an air atmosphere of -25 Pa to obtain a first sintered sample;

[0059] (2) Based on the mass of the first precursor, 30 wt% of the specific surface area is 18 m 2 / g, D50 is 5μm Ni 0.3 Co 0.1 Mn 0.6 (OH)2, 0.05wt% Al2O3, the above raw materials are added to the first sintered sample at the same time, and continued to mix using a high-speed mixer to obtain a second mixed sample, which is sintered at 950°C in an air atmosphere of -25Pa and kept warm for 15 hours. After crushing, grinding and screening to remove iron, the high-capacity and long-cycle sodium ion battery positive electrode material is obtained.

[0060] Figure 1 The scanning electron microscope image of the high-capacity, long-cycle sodium-ion battery positive electrode material prepared in this embodiment is shown. As can be seen from the figure, the prepared high-capacity, long-cycle sodium-ion battery positive electrode material has a spherical morphology and is a secondary particle formed by the agglomeration of primary particles.

[0061] Example 2

[0062] This embodiment provides a method for preparing a high-capacity, long-cycle sodium-ion battery cathode material, the preparation method comprising the following steps:

[0063] (1) According to the Na element and Ni in sodium bicarbonate 0.18 Co 0.1 Mn 0.72 The molar ratio of the metal elements in (OH)2 is 1.25. Sodium carbonate and a specific surface area of ​​36m 2 / g, D50 is 8.5μm Ni 0.18 Co 0.1 Mn 0.72 (OH)2, the above raw materials were mixed with a high-speed mixer to obtain a first mixed sample, and sintered at 600 ° C for 8 h in an oxygen atmosphere of -20 Pa to obtain a first sintered sample;

[0064] (2) Based on the mass of the first precursor, 23 wt% of the specific surface area is weighed to be 16 m 2 / g, D50 is 4.5μm Ni 0.32 Co 0.1 Mn 0.58 (OH)2, weigh 0.09wt% ZrO4, add the above raw materials to the first sintered sample at the same time, continue mixing with a high-speed mixer to obtain a second mixed sample, sinter at 850°C under an oxygen atmosphere of -20Pa, keep warm for 20h, and after crushing, grinding and screening to remove iron, obtain the high-capacity long-cycle sodium ion battery positive electrode material.

[0065] Example 3

[0066] This embodiment provides a method for preparing a high-capacity, long-cycle sodium-ion battery cathode material, the preparation method comprising the following steps:

[0067] (1) According to the Na and Ni in sodium oxalate 0.12 Co 0.1 Zr 0.03 Mn 0.75 The molar ratio of the metal elements in (OH)2 is 1.45. Sodium carbonate and a specific surface area of ​​40m 2 / g, D50 is 9.5μm Ni 0.12 Co 0.1 Zr 0.03 Mn 0.75 (OH)2, the above raw materials were mixed with a high-speed mixer to obtain a first mixed sample, and sintered at 750 ° C for 4 h in an air atmosphere of -28 Pa to obtain a first sintered sample;

[0068] (2) Based on the mass of the first precursor, 38 wt% of the specific surface area is weighed as 20 m 2 / g, D50 is 6μm Ni 0.26 Co 0.1 Zr 0.01 Mn 0.63(OH)2, weigh 0.008wt% Nb2O5, add the above raw materials to the first sintered sample at the same time, continue mixing with a high-speed mixer to obtain a second mixed sample, sinter at 1050°C in an air atmosphere of -28Pa, keep warm for 12h, and after crushing, grinding and screening to remove iron, obtain the high-capacity long-cycle sodium ion battery positive electrode material.

[0069] Example 4

[0070] This embodiment provides a method for preparing a high-capacity, long-cycle sodium-ion battery positive electrode material. The difference between the preparation method and Example 1 is that in step (1), the sintering temperature of the first mixed sample is 950° C., that is, the same as the sintering temperature in step (2). The remaining preparation methods and parameters are consistent with Example 1.

[0071] Example 5

[0072] This embodiment provides a method for preparing a high-capacity, long-cycle sodium-ion battery positive electrode material. The difference between the preparation method and Example 1 is that in step (1), the sintering temperature of the first mixed sample is 500° C., and the remaining preparation methods and parameters are consistent with Example 1.

[0073] Example 6

[0074] This embodiment provides a method for preparing a high-capacity, long-cycle sodium-ion battery positive electrode material. The difference between the preparation method and Example 1 is that in step (1), the molar ratio of the Na element to the metal element is 1.1:1, and the remaining preparation methods and parameters are consistent with Example 1.

[0075] Example 7

[0076] This embodiment provides a method for preparing a high-capacity, long-cycle sodium-ion battery positive electrode material. The difference between the preparation method and Example 1 is that in step (1), the molar ratio of the Na element to the metal element is 1.7:1, and the remaining preparation methods and parameters are consistent with Example 1.

[0077] Comparative Example 1

[0078] This comparative example provides a method for preparing a positive electrode material for a sodium ion battery. The difference between the preparation method and Example 1 is that step (1) of obtaining a first sintered sample is omitted, and Ni is directly 0.15 Co 0.1 Mn 0.75 (OH)2, sodium carbonate, Ni 0.3 Co 0.1 Mn 0.6 (OH)2 and Al2O3 were mixed together using a high-speed mixer, and the remaining preparation methods and parameters were consistent with those in Example 1.

[0079] Comparative Example 2

[0080] This comparative example provides a method for preparing a positive electrode material for a sodium ion battery. The difference between the preparation method and Example 1 is that in step (1), Ni 0.15 Co 0.1 Mn 0.75 The D50 of (OH)2 is 5 μm. In step (2), Ni 0.3 Co 0.1 Mn 0.6 The D50 of (OH)2 is 9 μm, and the rest of the preparation methods and parameters are consistent with those in Example 1.

[0081] Test Method

[0082] The high-capacity and long-cycle sodium ion battery positive electrode materials prepared in Examples 1 to 7 and the sodium ion battery positive electrode materials prepared in Comparative Examples 1 to 2 were respectively prepared into lithium ion button batteries, and the 0.1C first-cycle discharge specific capacity under 2-4.2V conditions and the 100 and 200 cycles of room temperature cycle performance under 2-4.2V 1C / 1C conditions were tested respectively. The test results are shown in Table 1.

[0083] Table 1

[0084]

[0085] The test results show that:

[0086] (1) It can be seen from Examples 1 to 7 that the 0.1C discharge specific capacity of the positive electrode materials prepared by the preparation method provided by the present invention is all above 122.32 mAh / g, the capacity retention rate of 1C cycle 100 cycles is all above 88.74%, and the capacity retention rate of 1C cycle 200 cycles is all above 84.92%. Preferably, further, it can be seen from Examples 1 to 3 that the 0.1C discharge specific capacity of the positive electrode materials prepared by the preparation method provided by the present invention is all above 134.90 mAh / g, the capacity retention rate of 1C cycle 100 cycles is all above 92.02%, and the capacity retention rate of 1C cycle 200 cycles is all above 87.00%, with higher capacity and excellent long-cycle performance;

[0087] (2) It can be seen from Examples 1 and 4 to 5 that if the sintering temperature of the first mixed sample is too high, the melting rate of the raw materials and the decomposition rate of the precursor are accelerated, making it difficult to fully mix and tending to grow directly, resulting in a decrease in discharge capacity. If the sintering temperature of the first mixed sample is too low, the raw materials are difficult to melt and the precursor is not completely decomposed, and the subsequent growth into a layered positive electrode material phase is not normal or the generated phase has poor crystallinity, which will reduce the overall electrochemical performance of the prepared positive electrode material.

[0088] (3) It can be seen from Examples 1 and 6-7 that if the ratio of the Na element to the metal element is too small, the capacity of the positive electrode material will be affected, resulting in a decrease in the capacity; if the ratio of the Na element to the metal element is too large, the prepared positive electrode material will be homogenized and gelled during the preparation of the positive electrode slurry, affecting the preparation of the positive electrode sheet, and both will reduce the overall electrochemical performance of the prepared positive electrode material.

[0089] (4) It can be seen from Example 1 and Comparative Examples 1 to 2 that in Comparative Example 1, directly mixing and sintering all the raw materials will cause the Na element to aggregate or segregate, and it cannot be evenly distributed in the positive electrode material; in Comparative Example 2, the median particle size of the first precursor is smaller than the median particle size of the second precursor. Since the particle size of the second precursor is larger, the diffusion path of the Na element in the second precursor is longer, so the Na element still cannot be evenly distributed in the positive electrode material, which will reduce the overall electrochemical performance of the prepared positive electrode material.

[0090] In summary, the present invention provides a high-capacity, long-cycle sodium-ion battery cathode material, and its preparation method and application. A composite high-Mn element precursor is used to reduce the use of transition precious metals and reduce costs. At the same time, the presence of the Mn element can not only stabilize the material structure, but some low-priced Mn can also participate in the redox reaction, contributing to the capacity of the cathode material; the use of two mixing and two sintering processes can make the Na element more evenly enter the bulk phase of the cathode material, and the cathode material is composed of secondary particles formed by uniform agglomeration of primary particles, with higher capacity and better long-cycle performance.

[0091] The applicant declares that the above is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the scope of protection and disclosure of the present invention.

Claims

1. A method for preparing a high-capacity, long-cycle sodium-ion battery cathode material, characterized in that: The preparation method comprises the following steps: (1) uniformly mixing a first precursor and a sodium source to obtain a first mixed sample, and performing a sintering operation to obtain a first sintered sample; (2) uniformly mixing the second precursor, the additive, and the first sintered sample of step (1) to obtain a second mixed sample, and performing secondary sintering to obtain the high-capacity and long-cycle sodium ion battery positive electrode material; Among them, the chemical general formula of the first precursor is Me x Mn y (OH)2, where x + y = 1 and 0.7 < y < 0.8; the chemical general formula of the second precursor is Me a Mn b (OH)2, where a + b = 1 and 0.55 < b < 0.65; the median particle size of the first precursor is greater than that of the second precursor; Me includes any one or a combination of at least two of Ni, Co, Al, Fe, Cu, Zr or Mg.

2. The preparation method according to claim 1, characterized in that The specific surface area of ​​the first precursor is 35-40 m 2 / g.

3. The preparation method according to claim 1, characterized in that The median particle size D50 of the first precursor is 8-10 μm.

4. The preparation method according to claim 1, characterized in that The sodium source in step (1) includes any one of sodium carbonate, sodium bicarbonate, sodium hydroxide or sodium oxalate, or a combination of at least two of them.

5. The preparation method according to claim 1, characterized in that In step (1), the molar ratio of Na in the sodium source to the overall metal elements in the first precursor is (1.2-1.6):

1.

6. The preparation method according to claim 1, characterized in that The sintering atmosphere of the primary sintering in step (1) includes air or oxygen.

7. The preparation method according to claim 1, characterized in that The sintering temperature of the primary sintering is 600-800°C.

8. The preparation method according to claim 1, characterized in that The holding time of the primary sintering is 2 to 8 hours.

9. The preparation method according to claim 1, characterized in that The sintering pressure of the primary sintering is -20~-30Pa.

10. The preparation method according to claim 1, characterized in that The specific surface area of ​​the second precursor is 15~20m 2 / g.

11. The preparation method according to claim 1, characterized in that The median particle size D50 of the second precursor is 4-6 μm.

12. The preparation method according to claim 1, characterized in that Based on the mass of the first precursor in step (1), the amount of the second precursor added is 20-40 wt%.

13. The preparation method according to claim 1, characterized in that The additive in step (2) includes any one of Al2O3, ZrO4, TiO2, MgO or Nb2O5, or a combination of at least two of them.

14. The preparation method according to claim 1, characterized in that Based on the mass of the first precursor in step (1), the amount of the additive added is 0.005-0.1 wt%.

15. The preparation method according to claim 1, characterized in that The sintering atmosphere for the secondary sintering in step (2) includes air or oxygen.

16. The preparation method according to claim 1, characterized in that The sintering temperature of the secondary sintering is 850-1100°C.

17. The preparation method according to claim 1, characterized in that The holding time of the secondary sintering is 10 to 20 hours.

18. The preparation method according to claim 1, characterized in that The sintering pressure of the secondary sintering is -20~-30Pa.

19. The preparation method according to claim 1, characterized in that The preparation method comprises the following steps: (1) The specific surface area is 35~40m 2 / g, a first precursor with a D50 of 8-10 μm and a sodium source are uniformly mixed to obtain a first mixed sample, and the mixed sample is sintered once at 600-800°C and -20--30 Pa for 2-8 hours to obtain a first sintered sample; Among them, the chemical general formula of the first precursor is Me x Mn y (OH)2, where x + y = 1 and 0.7 < y < 0.8; the Me in the Me x Mn y (OH)2 includes any one or a combination of at least two of Ni, Co, Al, Fe, Cu, Zr or Mg; the sodium source includes any one or a combination of at least two of sodium carbonate, sodium bicarbonate, sodium hydroxide or sodium oxalate; the molar ratio of Na in the sodium source to the total metal elements in the first precursor is (1.2 - 1.6):1; the mixing method includes mechanical mixing; the mechanical mixing includes ball milling; the sintering atmosphere for the first sintering includes air or oxygen; (2) The specific surface area is 15~20m 2 / g, a second precursor with a D50 of 4-6 μm, an additive, and the first sintered sample of step (1) are uniformly mixed to obtain a second mixed sample, which is subjected to secondary sintering at 850-1100°C and -20--30 Pa, and kept warm for 10-20 hours, and is crushed, ground, and sieved to remove iron, thereby obtaining the high-capacity long-cycle sodium ion battery positive electrode material; Among them, the chemical general formula of the second precursor is Me a Mn b (OH)2, a + b = 1, 0.55 < b < 0.65; the Me in the Me a Mn b (OH)2 includes any one or a combination of at least two of Ni, Co, Al, Fe, Cu, Zr or Mg; based on the mass of the first precursor in step (1), the addition amount of the second precursor is 20-40 wt%; the additive includes any one or a combination of at least two of Al2O3, ZrO4, TiO2, MgO or Nb2O5; based on the mass of the first precursor in step (1), the addition amount of the additive is 0.005-0.1 wt%; the mixing method includes mechanical mixing; the mechanical mixing includes ball milling; the sintering atmosphere of the secondary sintering includes air or oxygen.

20. A high-capacity, long-cycle sodium-ion battery cathode material, characterized in that: The high-capacity, long-cycle sodium-ion battery positive electrode material is prepared by the preparation method according to any one of claims 1 to 19.

21. The high-capacity, long-cycle sodium-ion battery cathode material according to claim 20, characterized in that: The high-capacity and long-cycle sodium ion battery cathode material is a secondary particle formed by agglomeration of primary particles.

22. A sodium ion battery, characterized in that: The sodium ion battery comprises the high-capacity, long-cycle sodium ion battery positive electrode material according to claim 20 or 21.

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