O3 high-voltage sodium ion battery positive electrode material and preparation method thereof

Abstract

The chemical formula of the positive electrode material is Naa (Ni2 / 5Fe1 / 5Mn2 / 5) bCacSrdCueTifLigZnhO2, a is greater than or equal to 0.95 and less than or equal to 1.1, b is greater than or equal to 0.75 and less than or equal to 0.9, c is greater than or equal to 0.006 and less than or equal to 0.007, d is greater than or equal to 0.003 and less than or equal to 0.004, e is greater than or equal to 0.03 and less than or equal to 0.05, f is greater than or equal to 0.08 and less than or equal to 0.12, g is greater than or equal to 0.008 and less than or equal to 0.012, and h is greater than or equal to 0.01 and less than or equal to 0.03. By doping calcium, strontium, copper, magnesium, titanium and zinc elements in the layered structure, the complex phase change of the positive electrode material in the charge-discharge cycle process is inhibited, and the cycle stability of the positive electrode material is improved; by regulating and controlling the molar weight of the doping element in the application range, the O3 type positive electrode material has high charge-discharge specific capacity and can maintain high working voltage.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of electrochemistry, in particular to an O3 high-voltage type sodium ion battery positive electrode material and a preparation method thereof. BACKGROUND

[0002] The sodium ion battery is currently attracting more and more attention and research due to excellent electrochemical performance, rich resources and low price.

[0003] However, in the prior art, there are still many problems in the synthesis process of the sodium ion battery positive electrode material, such as uneven distribution of doped elements, wide particle size distribution width, and thus low cycle stability of the positive electrode material. In addition, the sodium ion battery usually has a low working voltage, and due to the crystal structure of the positive electrode material itself, irreversible phase transition easily occurs during the charging and discharging process, which also limits the further development of the sodium ion battery.

[0004] Therefore, it is of great significance to develop a sodium ion positive electrode material with high charging and discharging specific capacity while maintaining a high working voltage, which will promote the large-scale commercial application of the sodium ion battery. SUMMARY

[0005] The application aims to provide an O3 high-voltage type sodium ion battery positive electrode material and a preparation method thereof, so that the sodium ion battery positive electrode material has high charging and discharging specific capacity while maintaining a high working voltage.

[0006] The specific technical solutions are as follows:

[0007] The first aspect of the application provides an O3 high-voltage type sodium ion battery positive electrode material, and the chemical formula of the positive electrode material is: Na a (Ni 2 / 5 Fe 1 / 5 Mn 2 / 5 ) b Ca c Sr d Cu e Ti f Li g Zn h O2, 0.95≤a≤1.1, 0.75≤b≤0.9, 0.006≤c≤0.007, 0.003≤d≤0.004, 0.03≤e≤0.05, 0.08≤f≤0.12, 0.008≤g≤0.012, 0.01≤h≤0.03. By doping calcium, strontium, copper, magnesium, titanium and zinc elements in the layered structure, the complex phase transition of the positive electrode material during the charging and discharging cycle process is inhibited, and the cycle stability of the positive electrode material is improved. By adjusting the molar amount of the doped elements within the above range, the positive electrode material has high charging and discharging specific capacity while maintaining a high working voltage.

[0008] In some embodiments of the present application, the Dv50 of the positive electrode material is 4-7 μm. By regulating the volume average particle size Dv50 of the positive electrode material within the above range, the present application is advantageous in making the positive electrode material have higher cycle stability.

[0009] In some embodiments of the present application, the sodium source of the positive electrode material is selected from at least one of sodium carbonate, sodium sulfate or sodium nitrate, and the nickel-iron-manganese source of the positive electrode material is selected from any one of the following: Ni 2 / 5 Fe 1 / 5 Mn 2 / 5 (OH)2, Ni 2 / 5 Fe 1 / 5 Mn 2 / 5 CO3 precursor material. By selecting the above materials as the sodium source of the positive electrode material, it is advantageous for sodium ions to uniformly diffuse in the positive electrode material to form a sodium ion layer; by selecting the above precursor material as the nickel-iron-manganese source of the positive electrode material, it is advantageous for the positive electrode material to form a layered structure.

[0010] In some embodiments of the present application, the calcium source of the positive electrode material is selected from at least one of calcium oxide, calcium carbonate or calcium hydroxide. By selecting the above materials as the calcium source of the positive electrode material, it is advantageous for improving the specific capacity and cycle stability of the positive electrode material.

[0011] In some embodiments of the present application, the strontium source of the positive electrode material is selected from at least one of strontium sulfate or strontium carbonate. By selecting the above materials as the strontium source of the positive electrode material, it is advantageous for stabilizing the crystal structure and inhibiting lattice distortion during the charging and discharging process, thereby improving the cycle stability and thermal stability of the positive electrode material.

[0012] In some embodiments of the present application, the copper source of the positive electrode material is selected from at least one of copper oxide or copper sulfate. By selecting the above materials as the copper source of the positive electrode material, it is advantageous for improving the energy density of the positive electrode material and inhibiting harmful phase change of the shell material during the charging and discharging process, thereby improving the structural stability of the positive electrode material.

[0013] In some embodiments of the present application, the titanium source of the positive electrode material is selected from at least one of titanium oxide or titanium tetrachloride. By selecting the above materials as the titanium source of the positive electrode material, it is advantageous for titanium elements to be uniformly doped into the positive electrode material, thereby being advantageous for generating a uniform and stable positive electrode material.

[0014] In some embodiments of the present application, the lithium source of the positive electrode material is selected from at least one of lithium carbonate, lithium hydroxide or lithium acetate. By selecting the above materials as the lithium source, it is advantageous for improving the ionic conductivity of the positive electrode material, smoothing the charging and discharging curve of the secondary battery, and improving the cycle performance of the secondary battery.

[0015] In some embodiments of this application, the zinc source for the cathode material is selected from at least one of zinc oxide or zinc sulfate. By selecting the above materials as the zinc source for the cathode material, it is beneficial for zinc to be uniformly doped into the cathode material, thereby improving the stability of the crystal structure, preventing the active material from falling off during charging and discharging, and thus improving the cycle stability of the cathode material.

[0016] A second aspect of this application provides a method for preparing an O3 high-voltage sodium-ion battery cathode material, wherein the method includes:

[0017] (1) According to Na a (Ni 2 / 5 Fe 1 / 5 Mn 2 / 5 ) b Ca c Sr d Cu e Ti f Li g Zn h The stoichiometric ratios of sodium, nickel-iron-manganese precursor, calcium, strontium, copper, titanium, lithium, and zinc in O2 are calculated by weighing out sodium source, nickel-iron-manganese precursor, calcium source, strontium source, copper source, titanium source, lithium source, and zinc source, respectively, where 0.95≤a≤1.1, 0.75≤b≤0.9, 0.006≤c≤0.007, 0.003≤d≤0.004, 0.03≤e≤0.05, 0.08≤f≤0.12, 0.008≤g≤0.012, and 0.01≤h≤0.03.

[0018] (2) The sodium source, nickel-iron-manganese precursor, calcium source, strontium source, copper source, titanium source, lithium source and zinc source weighed above are placed in a ball mill jar for ball milling. The ball mill speed is 300 rpm to 500 rpm and the ball milling time is 1 h to 5 h. Then, the mixture is vacuum dried at 80 °C for 24 h to obtain a mixed powder.

[0019] (3) The mixed powder is heated to 600°C to 700°C in an air or oxygen atmosphere at a first heating rate of 2°C to 5°C and held for 4 to 8 hours. Then, it is heated to 850°C to 950°C at a second heating rate of 2°C to 5°C and held for 10 to 18 hours.

[0020] (4) After cooling to room temperature at a rate of 2°C to 5°C, grind to obtain the positive electrode material Na. a (Ni 2 / 5 Fe 1 / 5Mn 2 / 5 ) b Ca c Sr d Cu e Ti f Lig Zn h O2.

[0021] This application improves the cycle stability of the cathode material by controlling the content and proportion of each element within the aforementioned range. Furthermore, by controlling the heating rate, cooling rate, and holding time, it facilitates the production of cathode materials with uniform particle size distribution, suitable size, and stable structure. This application utilizes the synergistic effect of doping elements to enable the cathode material to maintain a high operating voltage while possessing a high charge / discharge specific capacity.

[0022] The beneficial effects of this application are:

[0023] This application provides an O3 high-voltage sodium-ion battery cathode material and its preparation method. The chemical formula of the cathode material is: Na a (Ni 2 / 5 Fe 1 / 5 Mn 2 / 5 ) b Ca c Sr d Cu e Ti f Li g Zn h O2, 0.95≤a≤1.1, 0.75≤b≤0.9, 0.006≤c≤0.007, 0.003≤d≤0.004, 0.03≤e≤0.05, 0.08≤f≤0.12, 0.008≤g≤0.012, 0.01≤h≤0.03. This application suppresses complex phase transitions in the cathode material during charge-discharge cycling by doping it with calcium, strontium, copper, magnesium, titanium, and zinc into a layered structure, thereby improving the cycle stability of the cathode material. By controlling the molar amount of the dopant elements within the above range, and utilizing the synergistic effect of the dopant elements, the O3-type cathode material can maintain a high operating voltage while exhibiting a high charge-discharge specific capacity.

[0024] 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

[0025] 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.

[0026] Figure 1 The charge-discharge curves of the secondary battery in Embodiment 1 of this application at 0.1C and 2V-4.2V for the first and 500th cycles are shown.

[0027] Figure 2 This is a particle size test diagram of the cathode material in Example 1 of this application. Detailed Implementation

[0028] 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:

[0029] The first aspect of this application provides an O3 high-voltage sodium-ion battery cathode material, the chemical formula of which is: Na a (Ni 2 / 5 Fe 1 / 5 Mn 2 / 5 ) b Ca c Sr d Cu e Ti f Li g Zn h O2, 0.95≤a≤1.1, 0.75≤b≤0.9, 0.006≤c≤0.007, 0.003≤d≤0.004, 0.03≤e≤0.05, 0.08≤f≤0.12, 0.008≤g≤0.012, 0.01≤h≤0.03. By doping the layered structure with calcium, strontium, copper, magnesium, titanium, and zinc, the complex phase transitions in the cathode material during charge-discharge cycling are suppressed, thus improving the cycle stability of the cathode material. By controlling the molar amount of the doping elements within the above range, the cathode material can maintain a high operating voltage while exhibiting a high charge-discharge specific capacity.

[0030] In some embodiments of this application, the Dv50 of the cathode material is 4 μm to 7 μm. By controlling the volume average particle size Dv50 of the cathode material within the above range, this application facilitates higher cycle stability of the cathode material.

[0031] In some embodiments of this application, the sodium source of the positive electrode material is selected from at least one of sodium carbonate, sodium sulfate, or sodium nitrate, and the nickel-iron-manganese source of the positive electrode material is selected from Ni 2 / 5 Fe 1 / 5 Mn 2 / 5 (OH)2, Ni 2 / 5 Fe 1 / 5 Mn 2 / 5Any one of the CO3 precursor materials. By selecting the above materials as the sodium source of the positive electrode material, it is beneficial for sodium ions to diffuse uniformly in the positive electrode material to form a sodium ion layer; by selecting the above precursor materials as the nickel-iron-manganese source of the positive electrode material, it is beneficial for the positive electrode material to form a layered structure.

[0032] In some embodiments of this application, the calcium source for the cathode material is selected from at least one of calcium oxide, calcium carbonate, or calcium hydroxide. Selecting these materials as the calcium source for the cathode material is beneficial for improving the specific capacity and cycle stability of the cathode material.

[0033] In some embodiments of this application, the strontium source of the cathode material is selected from at least one of strontium sulfate or strontium carbonate. By selecting the above materials as the strontium source of the cathode material, it is beneficial to stabilize the crystal structure, suppress lattice distortion during the charge and discharge process, thereby improving the cycle stability and thermal stability of the cathode material.

[0034] In some embodiments of this application, the copper source for the cathode material is selected from at least one of copper oxide or copper sulfate. By selecting the above materials as the copper source for the cathode material, it is beneficial to improve the energy density of the cathode material, suppress harmful phase transitions of the shell material during charging and discharging, and thus improve the structural stability of the cathode material.

[0035] In some embodiments of this application, the titanium source for the cathode material is selected from at least one of titanium oxide or titanium tetrachloride. By selecting the above materials as the titanium source for the cathode material, it is beneficial for titanium to be uniformly doped into the cathode material, thereby facilitating the generation of a uniform and stable cathode material.

[0036] 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. Using these materials as the lithium source 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.

[0037] In some embodiments of this application, the zinc source for the cathode material is selected from at least one of zinc oxide or zinc sulfate. By selecting the above materials as the zinc source for the cathode material, it is beneficial for zinc to be uniformly doped into the cathode material, thereby improving the stability of the crystal structure, preventing the active material from falling off during charging and discharging, and thus improving the cycle stability of the cathode material.

[0038] The second aspect of this application provides a method for preparing an O3 high-voltage sodium-ion battery cathode material, wherein the method includes: (1) according to Na a (Ni 2 / 5 Fe 1 / 5 Mn 2 / 5 ) b Ca c Srd Cu e Ti f Li g Zn h The stoichiometric ratios of sodium, nickel-iron-manganese precursor, calcium, strontium, copper, titanium, lithium, and zinc in O2 are used to weigh out sodium source, nickel-iron-manganese precursor, calcium source, strontium source, copper source, titanium source, lithium source, and zinc source, respectively, where 0.95≤a≤1.1, 0.75≤b≤0.9, 0.006≤c≤0.007, 0.003≤d≤0.004, 0.03≤e≤0.05, 0.08≤f≤0.12, 0.008≤g≤0.012, and 0.01≤h≤0.03; (2) the stoichiometric ratios of the sodium source, nickel-iron-manganese precursor, calcium source, and zinc source weighed out are used to weigh out the sodium source, nickel-iron-manganese precursor, calcium source, and zinc source, respectively. Strontium source, copper source, titanium source, lithium source and zinc source are placed in a ball mill jar for ball milling. The ball mill speed is 300 rpm to 500 rpm and the ball milling time is 1 h to 5 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 600 °C to 700 °C at a first heating rate of 2 °C to 5 °C under air or oxygen atmosphere and held for 4 h to 8 h. Then, it is heated to 850 °C to 950 °C at a second heating rate of 2 °C to 5 °C and held for 10 h to 18 h. (4) After cooling to room temperature at a cooling rate of 2 °C to 5 °C, it is ground to obtain the cathode material Na. a (Ni 2 / 5 Fe 1 / 5 Mn 2 / 5 ) b Ca c Sr d Cu e Ti f Li g Zn h O2. In the embodiments and comparative examples of this application, when weighing the sodium source in step (1), an additional 5 mol% is required on top of the original molar amount of sodium source to appropriately compensate for the sodium element loss during high-temperature sintering in step (3).

[0039] This application improves the cycle stability of the cathode material by controlling the content and proportion of each element within the aforementioned range. Furthermore, by controlling the heating rate, cooling rate, and holding time, it facilitates the production of cathode materials with uniform particle size distribution, suitable size, and stable structure. This application utilizes the synergistic effect of doping elements to enable the cathode material to maintain a high operating voltage while possessing a high charge / discharge specific capacity.

[0040] The secondary battery of 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.

[0041] The secondary battery of 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.

[0042] The positive electrode sheet of this application may include a positive electrode material layer and a positive electrode current collector. The positive electrode material layer of this application 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 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 can be achieved. For example, the mass ratio of positive electrode material, conductive agent, and binder in the positive electrode material layer is (70-95):(5-20):(5-10).

[0043] 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.

[0044] 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.

[0045] Example

[0046] 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.

[0047] Test methods and equipment:

[0048] Cathode material particle size testing:

[0049] The particle size distribution method follows GB / T 19077-2016. A laser particle size analyzer is used to test the Dv50 of the cathode material. During the test, the particle size is measured by measuring the intensity of the scattered light as the laser beam passes through the dispersed particle sample. The refractive index of the particles used in the test is 2.61. Each sample is tested three times, and the particle size Dv50 is obtained by averaging the three tests. The laser particle size analyzer model is FBS-1570ZXP, with a testing range of 0.1 μm to 500 μm.

[0050] Secondary battery 0.1C, 2V-4.2V initial charge / discharge specific capacity and cycle performance test:

[0051] 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 = 150mAh / 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 specific capacity obtained was recorded as the first discharge specific capacity.

[0052] The above steps were then repeated for 500 charge and discharge cycles, and the discharge specific capacity of the 500th cycle was recorded. Cycle capacity retention = (discharge specific capacity of the 500th cycle / discharge specific capacity of the first cycle) × 100%.

[0053] Example 1

[0054] <Preparation of cathode materials>

[0055] (1) According to Na 1.03 (Ni 2 / 5 Fe 1 / 5 Mn 2 / 5 ) 0.82 Ca 0.0068 Sr 0.0032 Cu 0.04 Ti 0.1 Li 0.01 Zn 0.02 The stoichiometric ratios of sodium, nickel-iron-manganese precursors, calcium, strontium, copper, titanium, lithium, and zinc in O2 are calculated by weighing out 0.53 mol of sodium carbonate (Na2CO3) and 0.82 mol of Ni. 2 / 5 Fe 1 / 5 Mn 2 / 5 (OH)2, 0.0068 mol calcium oxide (CaO), 0.0032 mol strontium carbonate (SrCO3), 0.04 mol copper oxide (CuO), 0.1 mol titanium oxide (TiO2), 0.005 mol lithium carbonate (Li2CO3) and 0.02 mol zinc oxide (ZnO);

[0056] (2) The Na2CO3 and Ni weighed above 2 / 5 Fe 1 / 5 Mn 2 / 5 (OH)2, CaO, SrCO3, CuO, TiO2, Li2CO3 and ZnO were placed in a ball mill jar and ball milled at a speed of 400 rpm for 3 hours. The mixture was then vacuum dried at 80°C for 24 hours to obtain a mixed powder.

[0057] (3) The mixed powder was heated to 650°C at a first heating rate of 3.5°C and held for 6 hours in an oxygen atmosphere, and then heated to 900°C at a second heating rate of 3.5°C and held for 15 hours.

[0058] (4) After cooling to room temperature at a rate of 3.5℃, the material is ground by an air jet mill for 1.5 hours to achieve a particle size Dv50 of approximately [value missing]. Figure 2 With a thickness of 6 μm, the cathode material Na was obtained. 1.03 (Ni 2 / 5 Fe 1 / 5 Mn 2 / 5 ) 0.82 Ca 0.0068 Sr 0.0032 Cu 0.04 Ti 0.1 Li 0.01 Zn 0.02 O2.

[0059] <Preparation of the positive electrode>

[0060] The prepared positive electrode material was mixed with polyvinylidene fluoride (PVDF) and conductive carbon black (SP) at a mass ratio of 80:10:10, and N-methylpyrrolidone (NMP) was added as a solvent. After stirring evenly, the mixture was coated on 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.

[0061] <Preparation of Electrolyte>

[0062] 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.

[0063] <Preparation of the diaphragm>

[0064] A porous polypropylene film with a thickness of 12μm was used.

[0065] <Preparation of Sodium-ion Batteries>

[0066] 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.

[0067] Examples 2 to 17

[0068] Except for the control of the stoichiometric ratios of sodium, nickel-iron-manganese precursor, calcium, strontium, copper, titanium, lithium, and zinc in the <Preparation of Cathode Material> section, as shown in Table 1, all other aspects are the same as in Example 1.

[0069] Examples 18 to 19

[0070] Except for adjusting the types of raw materials such as sodium, nickel-iron-manganese precursor, calcium, strontium, copper, titanium, lithium, and zinc 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 first stage heating temperature and holding time, the second stage heating temperature and holding time, the heating rate and cooling rate of the first and second stages, the sintering atmosphere, and the grinding time after sintering in Table 2, the rest is the same as in Example 1.

[0071] Comparative Examples 1 to 2

[0072] Except for adjusting the stoichiometric ratios of sodium, nickel-iron-manganese precursor, calcium, strontium, copper, titanium, lithium, and zinc in the <Preparation of Cathode Material> section as shown in Table 1, the rest is the same as in Example 1.

[0073] Table 1

[0074]

[0075]

[0076] Table 2

[0077]

[0078]

[0079] Table 3

[0080]

[0081] Referring to Tables 1 to 3, and from Examples 1 to 19 and Comparative Examples 1 to 2, it can be seen that this application, by doping the layered structure of the cathode material with calcium, strontium, copper, magnesium, titanium, and zinc, suppresses complex phase transitions during charge-discharge cycles and improves the cycle stability of the cathode material. By controlling the molar amount of the doping elements within the scope of this application, and utilizing the synergistic effect between the doping elements, the O3-type cathode material can maintain a high operating voltage while exhibiting a high charge-discharge specific capacity.

[0082] Specifically, as can be seen from Examples 1 to 19 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 a (Ni 2 / 5 Fe 1 / 5 Mn 2 / 5 ) b Ca c Sr d Cu e Ti f Li g Zn h O2, 0.95≤a≤1.1, 0.75≤b≤0.9, 0.006≤c≤0.007, 0.003≤d≤0.004, 0.03≤e≤0.05, 0.08≤f≤0.12, 0.008≤g≤0.012, 0.01≤h≤0.03, is beneficial for improving the discharge specific capacity of the positive electrode material while maintaining a high operating 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, the discharge specific capacity in the first cycle is 155 mAh / g, the discharge specific capacity in the 500th cycle is 144 mAh / g, and the capacity retention rate after 500 cycles is 92%, indicating that it has good cycle stability. Figure 2 This is a particle size distribution chart of the cathode material in Example 1 of this application. Figure 2 As can be seen from the data, the volume average particle size Dv50 of the cathode material in Example 1 is 6 μm, indicating that the cathode material prepared by adjusting the process parameters within the scope of this application has a smaller particle size distribution width and a more uniform particle size.

[0083] As can be seen from Examples 1, 18 to 19 in Tables 1 and 3, this application achieves a positive electrode material with high charge / discharge specific capacity while maintaining a high operating voltage by controlling the types of raw materials (sodium, nickel-iron-manganese precursor, calcium, strontium, copper, titanium, lithium, and zinc), the Dv50 of the cathode material, the ball mill speed and ball milling time when mixing the raw materials, the first stage heating temperature and holding time, the second stage heating temperature and holding time, the heating rate and cooling rate of the first and second stages, the sintering atmosphere, and the grinding time after sintering.

[0084] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover 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. Without further limitations, 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.

[0085] 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 positive electrode material for a high-voltage sodium-ion battery using O3, wherein, The chemical formula of the positive electrode material is: Na a (Ni 2 / 5 Fe 1 / 5Mn 2 / 5 ) b Ca c Sr d Cu e Ti f Li g Zn h O2, 0.95≤a≤1.1, 0.75≤b≤0.9, 0.006≤c≤0.007, 0.003≤d≤0.004, 0.03≤e≤0.05, 0.08≤f≤0.12, 0.008≤g≤0.012, 0.01≤h≤0.

03.

2. The O3 high-voltage sodium-ion battery cathode material according to claim 1, wherein, The Dv50 of the cathode material is 4 μm to 7 μm.

3. The O3 high-voltage 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 sulfate, or sodium nitrate, and the nickel-iron-manganese source of the positive electrode material is selected from Ni 2 / 5 Fe 1 / 5 Mn 2 / 5 (OH)2, Ni 2 / 5 Fe 1 / 5 Mn 2 / 5 Any one of the CO3 precursor materials.

4. The O3 high-voltage sodium-ion battery cathode material according to claim 1, wherein, The calcium source for the positive electrode material is selected from at least one of calcium oxide, calcium carbonate, or calcium hydroxide.

5. The O3 high-voltage sodium-ion battery cathode material according to claim 1, wherein, The strontium source of the cathode material is selected from at least one of strontium sulfate or strontium carbonate.

6. The O3 high-voltage sodium-ion battery cathode material according to claim 1, wherein, The copper source for the positive electrode material is selected from at least one of copper oxide or copper sulfate.

7. The O3 high-voltage 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 or titanium tetrachloride.

8. The O3 high-voltage 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. The O3 high-voltage sodium-ion battery cathode material according to claim 1, wherein, The zinc source for the positive electrode material is selected from at least one of zinc oxide or zinc sulfate.

10. A method for preparing an O3 high-voltage sodium-ion battery cathode material according to any one of claims 1 to 9, wherein, The method includes: (1) According to Na a (Ni 2 / 5 Fe 1 / 5 Mn 2 / 5 ) b Ca c Sr d Cu e Ti f Li g Zn h The stoichiometric ratios of sodium, nickel-iron-manganese precursor, calcium, strontium, copper, titanium, lithium, and zinc in O2 are calculated by weighing out sodium source, nickel-iron-manganese precursor, calcium source, strontium source, copper source, titanium source, lithium source, and zinc source, respectively, where 0.95≤a≤1.1, 0.75≤b≤0.9, 0.006≤c≤0.007, 0.003≤d≤0.004, 0.03≤e≤0.05, 0.08≤f≤0.12, 0.008≤g≤0.012, and 0.01≤h≤0.

03. (2) The sodium source, nickel-iron-manganese precursor, calcium source, strontium source, copper source, titanium source, lithium source and zinc source weighed above are placed in a ball mill jar for ball milling. The ball mill speed is 300 rpm to 500 rpm and the ball milling time is 1 h to 5 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 600°C to 700°C in an air or oxygen atmosphere at a first heating rate of 2°C to 5°C and held for 4 to 8 hours. Then, it is heated to 850°C to 950°C at a second heating rate of 2°C to 5°C and held for 10 to 18 hours. (4) After cooling to room temperature at a rate of 2°C to 5°C, grind for 1 to 2 hours to obtain the positive electrode material Na. a (Ni 2 / 5Fe 1 / 5 Mn 2 / 5 ) b Ca c Sr d Cu e Ti f Li g Zn h O2.

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