P2-type sodium-ion battery positive electrode material resistant to high-voltage circulation and preparation method of P2-type sodium-ion battery positive electrode material

Abstract

The invention provides a P2-type sodium-ion battery positive electrode material resistant to high-voltage circulation and a preparation method thereof, the chemical formula of the positive electrode material is NaxNiyMnzTihAliLijO2, 0.7 < = x < = 0.9, 0.2 < = y < = 0.27, 0.5 < = z < = 0.7, 0.02 < = h < = 0.07, 0.01 < = i < = 0.05, 0.05 < = j < = 0.1. By doping titanium, aluminum and lithium elements in the layered structure, the P2-type positive electrode material has relatively good structural stability in a high-voltage charge-discharge cycle process, and by regulating the molar weight of each doped element in the application range, the P2-type positive electrode material has good cycle stability under high voltage.

Description

Technical Field

[0001] This application relates to the field of electrochemical technology, and in particular to a high-voltage cycling resistant P2 type sodium-ion battery cathode material and its preparation method. Background Technology

[0002] With the rapid development of the new energy industry, lithium resources in nature are constantly decreasing, making it difficult to meet current market demand. Sodium resources, on the other hand, have advantages such as abundant reserves and low cost. Sodium-ion batteries also have excellent electrochemical properties and have shown potential as the next generation of energy storage batteries.

[0003] Sodium-ion batteries typically consist of components such as a positive electrode, a negative electrode, an electrolyte, a separator, and a casing. Among these, the positive electrode material is crucial to battery performance. Layered metal oxides, due to their simple structure, exhibit excellent cycle stability and rate performance, making them suitable for operation in low-temperature and high-rate environments. Therefore, they have become one of the most widely studied types of positive electrode materials for sodium-ion batteries in recent years. Based on their structure and sodium content, layered metal oxides can be divided into two main categories: P2-type and O3-type. Among these, P2-type positive electrode materials, with their lower sodium content, exhibit better rate performance due to their wide ion channels, which result in less resistance and a faster rate of sodium ion insertion / extraction during cycling.

[0004] However, in the existing technology, P2 type cathode materials are prone to crystal phase transitions during cycling, which limits the promotion and application of P2 type sodium nickel manganese-based oxide cathode materials. Summary of the Invention

[0005] The purpose of this application is to provide a P2 type sodium-ion battery cathode material with high voltage cycling resistance and its preparation method, so that the sodium-ion battery cathode material has good cycle stability under high voltage.

[0006] The specific technical solution is as follows:

[0007] The first aspect of this application provides a high-voltage cycling resistant P2-type sodium-ion battery cathode material, the chemical formula of which is: Na x Ni y Mn z Ti h Al i Li jO2, where 0.7≤x≤0.9, 0.2≤y≤0.27, 0.5≤z≤0.7, 0.02≤h≤0.07, 0.01≤i≤0.05, and 0.05≤j≤0.1. This application improves the structural stability of the P2-type cathode material during high-voltage charge-discharge cycles by doping it with titanium, aluminum, and lithium in a layered structure. By controlling the molar amounts of the doping elements within the aforementioned range, the P2-type cathode material exhibits good cycle stability under high voltage.

[0008] In some embodiments of this application, the Dv50 of the cathode material is 6 μm to 10 μm. By controlling the volume average particle size Dv50 of the sodium-ion battery cathode material within the above range, it is beneficial to improve the electrochemical and mechanical properties of the cathode material, shorten the diffusion path of sodium ions within the cathode material crystal, and also enable the cathode material to have sufficient active surface, thereby improving the cycle performance and rate performance of the secondary battery.

[0009] In some embodiments of this application, the sodium source of the cathode material is selected from at least one of sodium carbonate, sodium hydroxide, or sodium bicarbonate. By selecting the above materials as the sodium source of the cathode material, it is beneficial for sodium ions to diffuse uniformly in the layered structure of the cathode material to form a sodium ion layer, thereby improving the reversible specific capacity of the cathode material.

[0010] In some embodiments of this application, the nickel source for the cathode material is selected from at least one of nickel oxide, nickel nitrate, or nickel sulfate. Using these materials as the nickel source for the cathode material is beneficial for improving the sodium insertion / extraction capacity of the cathode material, thereby increasing the energy density of the secondary battery.

[0011] In some embodiments of this application, the manganese source of the cathode material is selected from at least one of manganese tetroxide, manganese nitrate, or manganese sulfate. By controlling the selection of the manganese source of the cathode material from the above materials, it is beneficial for manganese to be uniformly incorporated into the cathode material, thereby facilitating the generation of a uniform and stable cathode material.

[0012] In some embodiments of this application, the titanium source for the cathode material is selected from at least one of titanium oxide, titanium oxysulfate, or titanium tetrachloride. By controlling the selection of the titanium source for the cathode material from the above-mentioned materials, it is beneficial for titanium to be uniformly doped into the cathode material, thereby facilitating the generation of a uniform and stable cathode material. Titanium can also reduce the degree of ion mixing, suppress harmful phase transitions during charging and discharging, and improve the structural stability of the cathode material.

[0013] In some embodiments of this application, the aluminum source for the cathode material is selected from at least one of alumina or aluminum chloride. Using these materials as the aluminum source for the cathode material facilitates the uniform doping of aluminum ions into the cathode material, thereby promoting the formation of a uniform and stable cathode material. Aluminum doping also improves the cycle performance and thermal stability of the cathode material.

[0014] In some embodiments of this application, the lithium source for the cathode material is selected from at least one of lithium carbonate, lithium hydroxide, or lithium acetate. By selecting the above materials as the lithium source for the cathode material, it is beneficial for lithium ions to be uniformly doped into the cathode material, thereby facilitating the generation of a uniform and stable cathode material. Uniform doping of lithium ions into the cathode material also helps to improve the ionic conductivity of the cathode material, smooth the charge-discharge curve of the secondary battery, and improve the cycle performance of the secondary battery.

[0015] A second aspect of this application provides a method for preparing a P2-type sodium-ion battery cathode material resistant to high-voltage cycling, wherein the method includes:

[0016] (1) According to Na x Ni y Mn z Ti h Al i Li j The stoichiometric ratios of sodium, nickel, manganese, titanium, aluminum, and lithium in O2 are determined by weighing sodium, nickel, manganese, titanium, aluminum, and lithium sources respectively, where 0.7≤x≤0.9, 0.2≤y≤0.27, 0.5≤z≤0.7, 0.02≤h≤0.07, 0.01≤i≤0.05, and 0.05≤j≤0.1; (2) the weighed sodium, nickel, manganese, titanium, aluminum, and lithium sources are placed in... The mixture is ball-milled in a ball mill jar at a speed of 400 rpm to 800 rpm for 2 to 4 hours. Then it is vacuum-dried at 80°C for 24 hours to obtain a mixed powder. (3) The mixed powder is heated to 900°C to 1000°C in air at a heating rate of 2°C to 5°C and held for 10 to 18 hours. (4) After cooling to room temperature at a cooling rate of 2°C to 5°C, it is ground for 0.5 to 1.5 hours to obtain the positive electrode material Na. x Ni y Mn z Ti h Al i Li jO2. This application improves the uniformity of metal doping by adjusting the ball mill speed and ball milling time, which is beneficial to the uniform distribution of the three doped metal ions: titanium, lithium, and aluminum. At the same time, by adjusting the heating rate, cooling rate, heating temperature, holding time, cooling rate, and grinding time after sintering, it is beneficial to obtain cathode materials with uniform particle size distribution and uniform element doping.

[0017] The beneficial effects of this application are:

[0018] This application provides a high-voltage cycling resistant P2-type sodium-ion battery cathode material and its preparation method. The chemical formula of the cathode material is: Na x Ni y Mn z Ti h Al i Li j O2, where 0.7≤x≤0.9, 0.2≤y≤0.27, 0.5≤z≤0.7, 0.02≤h≤0.07, 0.01≤i≤0.05, and 0.05≤j≤0.1. This application achieves good structural stability of the P2-type cathode material during high-voltage charge-discharge cycles by doping it with titanium, aluminum, and lithium elements in a layered structure. By controlling the molar amounts of the doping elements within the range specified in this application, the P2-type cathode material exhibits good cycle stability under high voltage.

[0019] Of course, implementing any product or method of this application does not necessarily require achieving all of the advantages described above at the same time. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these drawings.

[0021] Figure 1 This is a charge-discharge curve of the secondary battery in Embodiment 1 of this application at 0.1C and 2V-4.2V.

[0022] Figure 2 This is a charge-discharge curve of the secondary battery in Embodiment 1 of this application at 1C and 2V-4.2V. Detailed Implementation

[0023] The technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application. Specific technical solutions are as follows:

[0024] The first aspect of this application provides a high-voltage cycling resistant P2-type sodium-ion battery cathode material, the chemical formula of which is: Na x Ni y Mn z Ti h Al i Li j O2, where 0.7≤x≤0.9, 0.2≤y≤0.27, 0.5≤z≤0.7, 0.02≤h≤0.07, 0.01≤i≤0.05, and 0.05≤j≤0.1. By doping the layered structure with titanium, aluminum, and lithium, the P2-type cathode material exhibits good structural stability during high-voltage charge-discharge cycles. By controlling the molar amounts of the doping elements within the aforementioned ranges, the P2-type cathode material demonstrates good cycle stability under high voltage.

[0025] In some embodiments of this application, the Dv50 of the cathode material is 6 μm to 10 μm. By controlling the volume average particle size Dv50 of the sodium-ion battery cathode material within the above range, it is beneficial to improve the electrochemical and mechanical properties of the cathode material, shorten the diffusion path of sodium ions within the cathode material crystal, and also enable the cathode material to have sufficient active surface, thereby improving the cycle performance and rate performance of the secondary battery.

[0026] In some embodiments of this application, the sodium source of the cathode material is selected from at least one of sodium carbonate, sodium hydroxide, or sodium bicarbonate. By selecting the above materials as the sodium source of the cathode material, it is beneficial for sodium ions to diffuse uniformly in the layered structure of the cathode material to form a sodium ion layer, thereby improving the reversible specific capacity of the cathode material.

[0027] In some embodiments of this application, the nickel source for the cathode material is selected from at least one of nickel oxide, nickel nitrate, or nickel sulfate. Using these materials as the nickel source for the cathode material is beneficial for improving the sodium insertion / extraction capacity of the cathode material, thereby increasing the energy density of the secondary battery.

[0028] In some embodiments of this application, the manganese source of the cathode material is selected from at least one of manganese tetroxide, manganese nitrate, or manganese sulfate. By controlling the selection of the manganese source of the cathode material from the above materials, it is beneficial for manganese to be uniformly incorporated into the cathode material, thereby facilitating the generation of a uniform and stable cathode material.

[0029] In some embodiments of this application, the titanium source for the cathode material is selected from at least one of titanium oxide, titanium oxysulfate, or titanium tetrachloride. By controlling the selection of the titanium source for the cathode material from the above-mentioned materials, it is beneficial for titanium to be uniformly doped into the cathode material, thereby facilitating the generation of a uniform and stable cathode material. Titanium can also reduce the degree of ion mixing, suppress harmful phase transitions during charging and discharging, and improve the structural stability of the cathode material.

[0030] In some embodiments of this application, the aluminum source for the cathode material is selected from at least one of alumina or aluminum chloride. Using these materials as the aluminum source for the cathode material facilitates the uniform doping of aluminum ions into the cathode material, thereby promoting the formation of a uniform and stable cathode material. Aluminum doping also improves the cycle performance and thermal stability of the cathode material.

[0031] In some embodiments of this application, the lithium source for the cathode material is selected from at least one of lithium carbonate, lithium hydroxide, or lithium acetate. By selecting the above materials as the lithium source for the cathode material, it is beneficial for lithium ions to be uniformly doped into the cathode material, thereby facilitating the generation of a uniform and stable cathode material. Uniform doping of lithium ions into the cathode material also helps to improve the ionic conductivity of the cathode material, smooth the charge-discharge curve of the secondary battery, and improve the cycle performance of the secondary battery.

[0032] The second aspect of this application provides a method for preparing a P2-type sodium-ion battery cathode material resistant to high-voltage cycling, wherein the method includes: (1) preparing a material according to the Na... x Ni y Mn z Ti h Al i Li j The stoichiometric ratios of sodium, nickel, manganese, titanium, aluminum, and lithium in O2 are determined by weighing sodium, nickel, manganese, titanium, aluminum, and lithium sources respectively, where 0.7≤x≤0.9, 0.2≤y≤0.27, 0.5≤z≤0.7, 0.02≤h≤0.07, 0.01≤i≤0.05, and 0.05≤j≤0.1; (2) the weighed sodium, nickel, manganese, titanium, aluminum, and lithium sources are placed in... The mixture is ball-milled in a ball mill jar at a speed of 400 rpm to 800 rpm for 2 to 4 hours. Then it is vacuum-dried at 80°C for 24 hours to obtain a mixed powder. (3) The mixed powder is heated to 900°C to 1000°C in air at a heating rate of 2°C to 5°C and held for 10 to 18 hours. (4) After cooling to room temperature at a cooling rate of 2°C to 5°C, it is ground for 0.5 to 1.5 hours to obtain the positive electrode material Na. x Ni y Mn z Ti h Ali Li j O2.

[0033] In the embodiments and comparative examples of this application, when weighing the sodium source in step (1), an additional 5 mol% excess of sodium source is required on top of the original molar amount to appropriately compensate for the element loss during high-temperature sintering in step (3).

[0034] This application improves the uniformity of metal doping by adjusting the ball mill speed and ball milling time, which is beneficial to the uniform distribution of the three doped metal ions: titanium, lithium and aluminum. At the same time, by adjusting the heating rate, cooling rate, heating temperature and holding time, cooling rate and grinding time after sintering, it is beneficial to obtain cathode materials with uniform particle size distribution and uniform element doping.

[0035] The secondary battery in this application also includes a separator. This application does not impose any particular restrictions on the separator, and those skilled in the art can choose one according to actual needs, as long as it can achieve the purpose of this application. For example, the material of the separator may include, but is not limited to, at least one of polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), cellulose, polyimide (PI), or polyamide; the type of separator may include, but is not limited to, at least one of dry membrane, microporous membrane, composite membrane, rolled membrane, or spun membrane.

[0036] The secondary battery in this application also includes an electrolyte. This application does not impose any particular limitations on the electrolyte; those skilled in the art can choose according to actual needs, as long as the purpose of this application is achieved. For example, at least one of ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), vinylene carbonate (VC), or fluoroethylene carbonate (FEC) can be mixed in a certain mass ratio to obtain a non-aqueous organic solvent, and then a sodium salt can be added to dissolve and mix evenly. This application does not impose any particular limitations on the above-mentioned "mass ratio," as long as the purpose of this application is achieved. This application does not limit the type of sodium salt, as long as the purpose of this application is achieved. For example, the sodium salt may include at least one of sodium hexafluorophosphate (NaPF6), sodium perchlorate (NaClO4), sodium tetraphenylborate [NaB(C6H5)4], sodium trifluoromethanesulfonate (NaCF3SO3), sodium fluorosilicate (NaSiF6), sodium bis(trifluoromethanesulfonyl)imide (NaTFSI), sodium dioxolaneborate (NaBOB), or sodium difluorooxolaneborate (NaDFOB). This application does not impose any particular limitation on the concentration of the sodium salt in the electrolyte, as long as it achieves the purpose of this application. For example, the concentration of the sodium salt may be from 1.0 mol / L to 2.0 mol / L.

[0037] The positive electrode in this application may include a positive electrode material layer and a positive electrode current collector. The positive electrode material layer may also include a conductive agent and a binder. The conductive agent includes at least one of conductive carbon black, single-walled carbon nanotubes, multi-walled carbon nanotubes, carbon nanofibers, or graphene. The binder includes at least one of polyvinylidene fluoride, sodium polyacrylate, polyvinylpyrrolidone, polytetrafluoroethylene, polyvinylidene fluoride-hexafluoropropylene copolymer, or polypropylene. This application does not impose any particular limitation on the mass ratio of the positive electrode material, conductive agent, and binder in the positive electrode material layer; those skilled in the art can choose according to actual needs, as long as the purpose of this application is achieved. For example, the mass ratio of the positive electrode material, conductive agent, and binder in the positive electrode material layer is (70–95):(5–20):(5–10).

[0038] This application does not impose any particular limitation on the positive electrode current collector, as long as it achieves the purpose of this application. For example, the positive electrode current collector may comprise aluminum foil, aluminum alloy foil, or a composite current collector. This application also does not impose any particular limitation on the thickness of the positive electrode current collector, as long as it achieves the purpose of this application. For example, the thickness of the positive electrode current collector may be from 5 μm to 20 μm. In this application, the positive electrode active material layer may be disposed on one surface or on two surfaces in the thickness direction of the positive electrode current collector. It should be noted that the term "surface" here can refer to the entire area of ​​the positive electrode current collector or only a portion thereof; this application does not impose any particular limitation, as long as the purpose of this application is achieved.

[0039] This application does not impose any particular limitation on the preparation method of the positive electrode sheet. Any preparation method known in the art can be selected, as long as it can achieve the purpose of this application. For example, the preparation method of the positive electrode sheet includes, but is not limited to, the following steps: dispersing the active material, conductive agent and binder in N-methylpyrrolidone (NMP) solvent and mixing to form a uniform positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector; and obtaining the positive electrode sheet after drying, cold pressing, cutting, slitting and re-drying.

[0040] Example

[0041] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below.

[0042] Test methods and equipment:

[0043] Secondary battery discharge specific capacity test at 0.1C and 2V-4.2V:

[0044] The cathode materials from each embodiment and comparative example were assembled into sodium-ion coin cells, and then charge-discharge tests were performed using the LAND CT3002A battery testing system: at room temperature, the cells were charged at a constant current of 0.1C (1C = 120mAh / g) until the voltage reached 4.2V, and then charged at a constant voltage of 4.2V until the current dropped below 0.05C, bringing them to a full charge state of 4.2V. Subsequently, the cells were discharged at a constant current of 0.1C until the voltage reached 2V. The obtained capacity was recorded as the discharge specific capacity.

[0045] Secondary battery 1C, 2V-4.2V discharge specific capacity and cycle performance test:

[0046] The cathode materials from each embodiment and comparative example were assembled into sodium-ion coin cells, and then charge-discharge tests were performed using the LAND CT3002A battery testing system: at room temperature, the cells were charged at a constant current of 1C (1C = 120mAh / g) until the voltage reached 4.2V, and then charged at a constant voltage of 4.2V until the current dropped below 0.05C, bringing them to a full charge state of 4.2V. Subsequently, the cells were discharged at a constant current of 0.1C until the voltage reached 2V. The obtained capacity was recorded as the discharge specific capacity.

[0047] The above steps were then repeated for 400 charge and discharge cycles, and the discharge specific capacity of the 400th cycle was recorded. Cycle capacity retention = (discharge specific capacity of the 400th cycle / discharge specific capacity of the first cycle) × 100%.

[0048] Example 1

[0049] <Preparation of cathode materials>

[0050] (1) According to Na 0.8 Ni 0.23 Mn 0.61 Ti 0.05 Al 0.03 Li 0.08 The stoichiometric ratios of sodium, nickel, manganese, titanium, aluminum, and lithium in O2 are determined by weighing out 0.42 mol sodium carbonate (Na2CO3), 0.23 mol nickel oxide (NiO), 0.204 mol manganese tetroxide (Mn3O4), 0.05 mol titanium oxide (TiO2), 0.015 mol aluminum oxide (Al2O3), and 0.04 mol lithium carbonate (Li2CO3), respectively.

[0051] (2) The Na2CO3, NiO, Mn3O4, TiO2, Al2O3 and Li2CO3 weighed above were placed into a ball mill jar for ball milling. The ball mill speed was 600 rpm and the ball milling time was 3 h. Then, the mixture was vacuum dried at 80℃ for 24 h to obtain a mixed powder.

[0052] (3) The mixed powder is heated to 950°C at a heating rate of 3.5°C in air and held at that temperature for 15 hours.

[0053] (4) After cooling to room temperature at a rate of 3.5℃, the material is ground by an air jet mill for 1 hour to achieve a particle size Dv50 of 8μm after sintering, thus obtaining the positive electrode material Na. 0.8 Ni 0.23 Mn 0.61 Ti 0.05 Al 0.03 Li 0.08 O2.

[0054] <Preparation of the positive electrode>

[0055] The prepared positive electrode material was mixed with polyvinylidene fluoride (PVDF) and conductive carbon black (SP) at a mass ratio of 70:20:10, and N-methylpyrrolidone (NMP) was added as a solvent. After stirring evenly, the mixture was coated onto one surface of the positive electrode current collector aluminum foil. Then, it was placed in an 80°C forced-air drying oven for 2 hours, and then placed in an 80°C vacuum drying oven for 24 hours. Finally, it was punched using a button cell slicing machine equipped with a 10mm diameter punching die to obtain the positive electrode sheet.

[0056] <Preparation of Electrolyte>

[0057] In a glove box protected by inert argon gas and with water and oxygen content <0.1ppm, 1mol / L sodium hexafluorophosphate (NaPF6) was dissolved in an organic solvent with a volume ratio of 1:1 of ethylene carbonate (EC): diethyl carbonate (DEC) and mixed thoroughly to obtain an electrolyte.

[0058] <Preparation of the diaphragm>

[0059] A porous polypropylene film with a thickness of 12μm was used.

[0060] <Preparation of Sodium-ion Batteries>

[0061] In a glove box protected by inert argon gas and with water and oxygen content <0.1ppm, button cells are assembled in the following order: negative electrode shell, sodium metal sheet, electrolyte, separator, electrolyte, positive electrode sheet, gasket, spring sheet, and positive electrode shell. Finally, the cells are packaged using a button cell packaging machine to obtain the CR2032 button sodium-ion battery used for testing.

[0062] Examples 2 to 13

[0063] Except for adjusting the stoichiometric ratios of sodium, nickel, manganese, titanium, aluminum, and lithium as shown in Table 1 in the <Preparation of Cathode Material>, everything else is the same as in Example 1.

[0064] Examples 14 to 15

[0065] Except for adjusting the types of raw materials (sodium, nickel, manganese, titanium, aluminum, and lithium) as shown in Table 1 in the <Preparation of Cathode Material>, and controlling the Dv50 of the cathode material, the ball mill speed and ball milling time during mixing of each raw material, the heating rate, heating temperature, holding time, cooling rate, and grinding time after sintering as shown in Table 2, everything else is the same as in Example 1.

[0066] Comparative Examples 1 to 2

[0067] Except for adjusting the stoichiometric ratios of sodium, nickel, manganese, titanium, aluminum, and lithium in the <Preparation of Cathode Materials> section as shown in Table 1, everything else is the same as in Example 1.

[0068] Table 1

[0069]

[0070] Table 2

[0071]

[0072] Table 3

[0073]

[0074] Referring to Tables 1 to 3, it can be seen from Examples 1 to 13 and Comparative Examples 1 to 2 that this application achieves good structural stability of the P2 type cathode material during high-voltage charge-discharge cycles by doping titanium, aluminum and lithium elements into the layered structure of the cathode material. By controlling the molar amount of the doping elements within the above range, the P2 type cathode material exhibits good cycle stability under high voltage.

[0075] Specifically, as can be seen from Examples 1 to 13 and Comparative Examples 1 to 2 in Tables 1 and 3, this application achieves the following by controlling the content and ratio of each element in the cathode material: Na x Ni y Mn z Ti h Al i Li jO2, 0.7≤x≤0.9, 0.2≤y≤0.27, 0.5≤z≤0.7, 0.02≤h≤0.07, 0.01≤i≤0.05, 0.05≤j≤0.1, is beneficial to improving the cycle stability of P2 type cathode materials under high voltage. Figure 1 The graph shows the charge-discharge performance test results of the sodium-ion battery in Example 1 at 0.1C and 2V-4.2V. Figure 1 As can be seen from this, the sodium-ion battery prepared using the high-voltage cycling resistant P2 type sodium-ion battery cathode material obtained in this application has a discharge specific capacity as high as 117 mAh / g. Figure 2 The graphs show the charge-discharge performance and cycle performance of the sodium-ion battery in Example 1 at 1C and 2V-4.2V. Figure 2 As can be seen from the above, the sodium-ion battery prepared using the high-voltage cycling resistant P2 type sodium-ion battery cathode material obtained in this application has a discharge specific capacity of up to 109 mAh / g, and the capacity retention rate is 91% after 400 cycles, indicating that it has good high-voltage cycling stability.

[0076] As can be seen from Examples 1, 14 to 15 in Tables 1 and 3, this application, by controlling the types of raw materials (sodium, nickel, manganese, titanium, aluminum and lithium), the Dv50 of the cathode material, the ball mill speed and ball milling time when mixing the raw materials, the heating rate, cooling rate, holding time and grinding time after sintering, and by controlling the above process parameters within the range of this application, is beneficial to obtaining a P2 type cathode material with better high-voltage cycle stability and higher discharge specific capacity.

[0077] It should be noted that, in this document, "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus 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 apparatus. Unless otherwise specified, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0078] The above are merely preferred embodiments of this application and are not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application are included within the scope of protection of this application.

Claims

1. A P2-type sodium-ion battery cathode material resistant to high-voltage cycling, wherein, The chemical formula of the positive electrode material is: Na x Ni y Mn z Ti h Al i Li j O2, where 0.7≤x≤0.9, 0.2≤y≤0.27, 0.5≤z≤0.7, 0.02≤h≤0.07, 0.01≤i≤0.05, and 0.05≤j≤0.

1.

2. The high-voltage cycling resistant P2-type sodium-ion battery cathode material according to claim 1, wherein, The Dv50 of the cathode material is 6 μm to 10 μm.

3. The high-voltage cycling resistant P2-type sodium-ion battery cathode material according to claim 1, wherein, The sodium source of the positive electrode material is selected from at least one of sodium carbonate, sodium hydroxide, or sodium bicarbonate.

4. The high-voltage cycling resistant P2-type sodium-ion battery cathode material according to claim 1, wherein, The nickel source for the positive electrode material is selected from at least one of nickel oxide, nickel nitrate, or nickel sulfate.

5. The high-voltage cycling resistant P2-type sodium-ion battery cathode material according to claim 1, wherein, The manganese source of the positive electrode material is selected from at least one of manganese tetroxide, manganese nitrate, or manganese sulfate.

6. The high-voltage cycling resistant P2-type sodium-ion battery cathode material according to claim 1, wherein, The titanium source for the positive electrode material is selected from at least one of titanium oxide, titanium oxysulfate, or titanium tetrachloride.

7. The high-voltage cycling resistant P2-type sodium-ion battery cathode material according to claim 1, wherein, The aluminum source for the positive electrode material is selected from at least one of aluminum oxide or aluminum chloride.

8. The high-voltage cycling resistant P2-type sodium-ion battery cathode material according to claim 1, wherein, The lithium source for the cathode material is selected from at least one of lithium carbonate, lithium hydroxide, or lithium acetate.

9. A method for preparing a P2-type sodium-ion battery cathode material resistant to high-voltage cycling according to any one of claims 1 to 8, wherein, The method includes: (1) According to Na x Ni y Mn z Ti h Al i Li j The stoichiometric ratios of sodium, nickel, manganese, titanium, aluminum, and lithium in O2 are determined by weighing out sodium, nickel, manganese, titanium, aluminum, and lithium sources, respectively, where 0.7≤x≤0.9, 0.2≤y≤0.27, 0.5≤z≤0.7, 0.02≤h≤0.07, 0.01≤i≤0.05, and 0.05≤j≤0.

1. (2) The sodium source, nickel source, manganese source, titanium source, aluminum source and lithium source weighed above are placed into a ball mill jar for ball milling. The ball mill speed is 400 rpm to 800 rpm and the ball milling time is 2 h to 4 h. Then, the mixture is vacuum dried at 80 °C for 24 h to obtain a mixed powder. (3) The mixed powder is heated to 900°C to 1000°C in air at a heating rate of 2°C to 5°C and held for 10h to 18h. (4) After cooling to room temperature at a rate of 2°C to 5°C, grind for 0.5 to 1.5 hours to obtain the cathode material Na. x Ni y Mn z Ti h Al i Li j O2.

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