High-capacity long-circulation sodium-ion battery positive electrode material as well as preparation method and application thereof

Abstract

The invention relates to a high-capacity long-cycle sodium ion battery positive electrode material and a preparation method and application thereof, the preparation method comprises the following steps: preparing a first precursor MexMny (OH) 2 with a large median particle size, x + y = 1, 0.7 lt; yt; Yt; 0.8 and a sodium source are mixed and sintered for the first time; the preparation method comprises the following steps: adding a second precursor MeaMnb (OH) 2 with a smaller median particle size, a + b = 1, 0.55 lt; blt; and 0.65, an additive and the obtained first sintering sample are mixed and subjected to secondary sintering, the sodium ion battery positive electrode material is obtained, and Me comprises any one or a combination of at least two of Ni, Co, Al, Fe, Cu, Zr or Mg. The composite high-Mn element precursor is adopted, use of transition precious metal is reduced, meanwhile, Mn can play a role in stabilizing the material structure, and part of low-valence Mn can participate in the oxidation-reduction reaction to contribute capacity; the two-time material mixing and two-time sintering processes are combined, so that the Na element distribution in the positive electrode material is more uniform.

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 positive electrode material, and a preparation method and application thereof. Background Art

[0002] As an alternative energy storage battery, sodium-ion batteries have gradually emerged in recent years and are expected to become a substitute for lithium-ion batteries in the field of large-scale energy storage and low-speed electric vehicles in the future. Sodium-ion batteries and lithium-ion batteries have similar working principles, and sodium resources are widely available and abundant. Compared with lithium resources, the price is more stable and cheaper, which is expected to alleviate the problem of limited lithium resources.

[0003] Among the components of the battery, the performance of the positive electrode material can often directly determine the final performance of the finished battery. Therefore, the development of low-cost, high-capacity, and good processing performance sodium-ion battery positive electrode materials is crucial for the practical application of sodium-ion batteries. The current types of sodium-ion battery positive electrode materials mainly include transition metal layered oxides, polyanionic compounds, and Prussian blue compounds. Among them, layered metal oxides have high reversible specific capacity, good electrochemical activity, and the production process is basically the same as that of lithium-ion battery positive electrode materials. They are considered to be the most promising sodium-ion battery positive electrode materials for large-scale industrialization.

[0004] The advantage of sodium-ion batteries over lithium-ion batteries lies mainly 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 positive electrode materials due to its low cost, abundant resources and favorable stability of 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 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, and by using precursors of different particle sizes and regulating the relationship between the particle size and the mass, the tap density, the compacted density and the rate performance are improved, but 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: Mix sodium oxalate, a cobalt source, an M source (at least one of Ti, Nb, Cu, Ni, V, and Cr), and an iron source, then ball-mill, press into tablets, and calcine to obtain a calcined powder; take an isopropanol salt solution and stir it with the calcined powder to obtain a reaction precursor; calcine the above reaction precursor to obtain the layered composite oxide. Although this preparation process can improve the rate performance and cycle performance to a certain extent by doping elements, its preparation process is complex and cumbersome, with a long cycle, and this mixing method cannot ensure the uniform dispersion of Na elements inside the layered composite oxide.

[0007] Therefore, how to provide a simple and effective preparation process to make Na elements uniformly distributed inside the cathode material, thereby improving the capacity and cycle performance of the layered sodium-ion cathode material, has become a technical problem to be solved urgently at present. Summary of the Invention

[0008] To solve the above technical problems, the present invention provides a cathode material for a high-capacity and long-cycle sodium-ion battery, its preparation method and application. By using a composite high-Mn element precursor, the use of transition noble metals is reduced, and the cost is lower. At the same time, the presence of Mn elements can not only play a role in stabilizing the material structure, but also some low-valent Mn can participate in redox reactions to contribute capacity to the cathode material; by adopting a two-stage mixing and two-stage sintering process, Na elements can enter the cathode material matrix more uniformly, and the cathode material is composed of secondary particles formed by the aggregation of uniform primary particles, with higher capacity and excellent long-cycle performance.

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

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

[0011] (1) Mix the first precursor and a sodium source evenly to obtain a first mixed sample, and perform a first sintering to obtain a first sintered sample;

[0012] (2) Mix the second precursor, an additive, and the first sintered sample obtained in step (1) evenly to obtain a second mixed sample, and perform a second sintering to obtain a cathode material for a high-capacity and long-cycle sodium-ion battery;

[0013] Among them, the chemical general formula of the first precursor is Me x Mn y (OH)2, x + y = 1, 0.7 < y < 0.8. For example, y can be 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, or 0.79, etc.; the chemical general formula of the second precursor is Mea Mn b (OH)2, where a + b = 1, 0.55 < b < 0.65. For example, b can be 0.56, 0.57, 0.58, 0.59, 0.60, 0.61, 0.62, 0.63 or 0.64, etc.; the median particle size of the first precursor is greater than that of the second precursor; the Me includes any one or a combination of at least two of Ni, Co, Al, Fe, Cu, Zr or Mg.

[0014] The present invention adopts two mixing processes and two sintering processes. The two sintering processes cooperate with each other to make the distribution of Na element in the cathode material of the high-capacity long-cycle sodium-ion battery more uniform. Since the particle size of the first precursor is larger and the diffusion path of Na ions into the bulk phase is longer, the sodium source and the first precursor are first sintered once to partially compound the first precursor and the sodium source. Na ions in part of the sodium source first diffuse into the bulk phase of the first precursor, and the remaining sodium source is uniformly left on the surface of the first precursor. Then the second precursor is added. Through secondary sintering, 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 distribution of Na element in the prepared cathode material more uniform. Moreover, the cathode material of the high-capacity long-cycle sodium-ion battery obtained by this preparation method is composed of secondary particles formed by the aggregation of uniform primary particles, with higher capacity and more excellent long-cycle performance.

[0015] The present invention adopts a composite high-Mn element precursor, reduces the use of transition precious metals, and has a lower cost. At the same time, the presence of Mn element can not only play a role in stabilizing the material structure, but also some low-valent Mn can participate in the redox reaction to contribute capacity to the cathode material; adopting two mixing processes and two sintering processes can make Na element enter the bulk phase of the cathode material more uniformly, and the cathode material is composed of secondary particles formed by the aggregation of uniform primary particles, with higher capacity and excellent long-cycle performance.

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

[0017] The so-called 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 - 40 m 2 / g, such as 35 m 2 / g, 36 m 2 / g, 37 m 2 / g, 38 m2 / g, 39m 2 / g or 40m 2 / g, etc.

[0019] Preferably, the median particle size D50 of the first precursor is 8-10 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 control the partial compounding of the first precursor and the sodium source, and then combined with the subsequent sintering process, the Na element is 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, causing the capacity to decrease; if the molar ratio is too large, that is, the content of the Na element is too high, it will cause the prepared positive electrode material to be homogenized and gelled 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 not completely 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 4-6 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 added amount of the second precursor is 20-40wt%, for example, 20wt%, 22wt%, 24wt%, 26wt%, 28wt%, 30wt%, 32wt%, 34wt%, 36wt%, 38wt% or 40wt%, 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 heat preservation time of the secondary sintering is 10 to 20 h, such as 10 h, 12 h, 14 h, 16 h, 18 h or 20 h, etc.

[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, etc.

[0041] Preferably, after the secondary sintering, it further includes crushing, grinding and iron removal by screening.

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

[0043] (1) Mix a first precursor with a specific surface area of 35 to 40 m 2 / g and D50 of 8 to 10 μm and a sodium source evenly to obtain a first mixed sample, and perform primary sintering at 600 to 800 °C and -20 to -30 Pa for 2 to 8 h to obtain a first sintered sample;

[0044] Among them, the chemical general formula of the first precursor is Me x Mn y (OH)2, x + y = 1, 0.7 < y < 0.8; 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 to 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) Mix a second precursor with a specific surface area of 15 to 20 m 2 / g and D50 of 4 to 6 μm, an additive and the first sintered sample obtained in step (1) evenly to obtain a second mixed sample, and perform secondary sintering at 850 to 1100 °C and -20 to -30 Pa for 10 to 20 h, and obtain the high-capacity long-cycle sodium-ion battery cathode material after crushing, grinding and iron removal by screening;

[0046] 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 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 20-40wt%; 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 0.005-0.1wt%; 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 a 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 and 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 adopts a composite high-Mn element precursor to reduce the use of transition noble metals and reduce costs; at the same time, the presence of the Mn element can not only stabilize the material structure, but also some low-priced Mn can participate in the redox reaction and contribute to the capacity of the positive electrode material;

[0051] 2) The present invention adopts two mixing and two sintering processes to make the Na element more evenly distributed in 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 better long cycle performance;

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

[0053] Figure 1 This is a scanning electron microscope image of the high-capacity and 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 is further described below in conjunction with the accompanying drawings and through specific implementation methods. However, the following examples are only 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 specified, 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 and long-cycle sodium ion battery positive electrode 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. Weigh 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 are mixed by a high-speed mixer to obtain a first mixed sample, and sintered at 700°C for 5h in an air atmosphere of -25Pa to obtain a first sintered sample;

[0059] (2) Based on the mass of the first precursor, weigh 30 wt% of the specific surface area of ​​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 with 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 and long-cycle sodium-ion battery positive electrode material prepared in this embodiment is shown. It can be seen from the figure that the prepared high-capacity and 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 and long-cycle sodium ion battery positive electrode 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. Weigh 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 are mixed by a high-speed mixer to obtain a first mixed sample, and sintered at 600°C for 8h in an oxygen atmosphere of -20Pa to obtain a first sintered sample;

[0064] (2) Based on the mass of the first precursor, weigh 23wt% of the specific surface area of ​​16m 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 into 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 in an oxygen atmosphere of -20Pa, keep warm for 20h, and after crushing, grinding and screening to remove iron, obtain the high-capacity and long-cycle sodium ion battery positive electrode material.

[0065] Example 3

[0066] This embodiment provides a method for preparing a high-capacity and long-cycle sodium ion battery positive electrode 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. Weigh 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 are mixed by a high-speed mixer to obtain a first mixed sample, and sintered at 750°C for 4 hours in an air atmosphere of -28Pa to obtain a first sintered sample;

[0068] (2) Based on the mass of the first precursor, weigh 38 wt% of the specific surface area of ​​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 into 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 and 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), and the rest of the preparation method 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 overall 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 overall 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 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 rest of the preparation method 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 the above 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 to 4.2V conditions and the 100 and 200 cycles of normal temperature cycle performance under 2 to 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 material 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 material 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 speed of the raw material and the decomposition speed of the precursor will be accelerated, making it difficult to fully mix and tend to grow directly, resulting in a decrease in discharge capacity. If the sintering temperature of the first mixed sample is too low, the raw material is difficult to melt and the precursor is not completely decomposed, and the subsequent growth into a layered positive electrode material phase cannot be 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 as a whole is too small, it will affect the capacity of the positive electrode material, resulting in a decrease in the capacity; if the ratio of the Na element to the metal element as a whole 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 that 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 and long-cycle sodium-ion battery positive electrode material and a preparation method and application thereof. A composite high-Mn element precursor is used to reduce the use of transition precious metals and reduce 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 to contribute to the capacity of the positive electrode material. The two-time mixing and two-time sintering process can make the Na element more evenly enter the positive electrode material body phase, and the positive electrode material is formed by uniformly agglomerated primary particles. The secondary particles have higher capacity and better long-cycle performance.

[0091] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope 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 shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for preparing a high-capacity long-cycle sodium ion battery positive electrode 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, 0.7 < y < 0.8; the chemical general formula of the second precursor is Me a Mn b (OH)2, where a + b = 1, 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 to 40 m 2 / g; Preferably, the median particle size D50 of the first precursor is 8-10 μm.

3. The preparation method according to claim 1 or 2, characterized in that: The sodium source in step (1) comprises any one of sodium carbonate, sodium bicarbonate, sodium hydroxide or sodium oxalate, or a combination of at least two thereof; Preferably, in step (1), the molar ratio of Na in the sodium source to the total metal elements in the first precursor is (1.2-1.6):

1.

4. The preparation method according to any one of claims 1 to 3, characterized in that The sintering atmosphere of the primary sintering in step (1) includes air or oxygen; Preferably, the sintering temperature of the primary sintering is 600-800°C; Preferably, the holding time of the primary sintering is 2 to 8 hours; Preferably, the sintering pressure of the primary sintering is -20 to -30 Pa.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The specific surface area of ​​the second precursor is 15 to 20 m 2 / g; Preferably, the median particle size D50 of the second precursor is 4 to 6 μm; Preferably, based on the mass of the first precursor in step (1), the amount of the second precursor added is 20-40 wt%.

6. The preparation method according to any one of claims 1 to 5, 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 thereof; Preferably, based on the mass of the first precursor in step (1), the amount of the additive added is 0.005-0.1 wt%.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The sintering atmosphere of the secondary sintering in step (2) includes air or oxygen; Preferably, the sintering temperature of the secondary sintering is 850-1100°C; Preferably, the holding time of the secondary sintering is 10 to 20 hours; Preferably, the sintering pressure of the secondary sintering is -20 to -30 Pa.

8. The preparation method according to claim 1, characterized in that: The preparation method comprises the following steps: (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 sintered once at 600 to 800°C and -20 to -30 Pa for 2 to 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 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, and secondary sintering is performed at 850 to 1100°C and -20 to -30 Pa, and the mixture is kept warm for 10 to 20 hours, and the high-capacity long-cycle sodium ion battery positive electrode material is obtained by crushing, grinding and screening to remove iron; Among them, 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 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 for the secondary sintering includes air or oxygen.

9. A high-capacity, long-cycle sodium-ion battery cathode material, characterized in that: The high-capacity and long-cycle sodium-ion battery positive electrode material is prepared by the preparation method according to any one of claims 1 to 8; The high-capacity and long-cycle sodium-ion battery positive electrode material is a secondary particle formed by agglomeration of primary particles.

10. A sodium ion battery, characterized in that: The sodium ion battery comprises the high-capacity and long-cycle sodium ion battery positive electrode material according to claim 9.

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