Sodium-electrode layered oxide positive electrode material and preparation method and application thereof

Abstract

The invention relates to a sodium electric layered oxide positive electrode material and a preparation method and application thereof, and relates to the technical field of positive electrode materials, the chemical formula of the sodium electric layered oxide positive electrode material is Na < 0.84 > Li < 0.1 > Ni < 0.27 > MnaTibO < 2 >; wherein 0.50 < = a < = 0.54, and 0.09 < = b < = 0.13. According to the invention, the sodium content proportion and the element composition in the positive electrode material are regulated and controlled by doping the transition metal with a proper proportion, so that the target sodium-electrode layered oxide positive electrode material is obtained, and the structural stability of the material in the cycle process and the charge-discharge capacity under high voltage are effectively improved; and secondly, through sintering process optimization and a secondary sintering process, the alkali content on the surface of the material is reduced, the microstructure of the material is regulated and controlled, the overall performance of the material is further improved, and the defects in the prior art are overcome.

Description

Technical Field

[0001] The present invention relates to the technical field of positive electrode materials, and in particular to a sodium electrode layered oxide positive electrode material and a preparation method and application thereof. Background Art

[0002] In recent years, with the rapid development of the new energy vehicle industry and large-scale electrochemical energy storage systems, the global demand for lithium resources has continued to increase, but the abundance of lithium resources is relatively low, and other alternative energy storage technologies and resources need to be explored. Compared with lithium resources, the earth has sodium resources that can be mined and utilized on a large scale, which can solve the shortage of lithium resources. The working principles of sodium-ion batteries and lithium-ion batteries are basically the same. Sodium-ion batteries are currently a good alternative to lead-acid batteries and lithium-ion batteries in some markets.

[0003] The advantages of sodium-ion batteries include abundant reserves of raw materials, easy extraction, low cost, high energy density, good rate performance, and excellent high and low temperature performance. They have obvious advantages in large-scale energy storage. In terms of energy density, the energy density of sodium-ion batteries is 100-160Wh / kg, which is higher than lead-acid batteries (30-50Wh / kg) and comparable to lithium iron phosphate (120-200Wh / kg). In terms of cycle life, sodium-ion batteries cycle more than 2,000 times, far exceeding the 300 times or so of lead-acid batteries. Therefore, judging from energy density and cycle life alone, sodium-ion batteries are expected to replace lead-acid batteries and lithium iron phosphate batteries in the fields of start-stop power supplies, 5G communication base stations, low-speed two-wheeled vehicles, energy storage, etc.

[0004] At present, the layered oxide cathode materials of sodium ion batteries are mainly divided into P2, P3, O3 and tunnel types. The market is mainly focused on the development of P2 and O3 materials. Due to the characteristics of the P2 phase layered oxide material itself, it belongs to the sodium-poor material. For example, the P2 phase structure of Na 0.67 Ni 0.33 Mn 0.67 O2 positive electrode material is Ni 2+ -Ni 4+ Although the continuous redox reaction has high specific capacity and working voltage, especially in the high-voltage region (>4.0V), the material will undergo a P2-O2 phase structural transition, which will cause huge volume changes and serious structural damage, so that its electrochemical performance becomes worse and worse during the cycle. O3 phase layered oxide materials will also undergo O3-P3 phase transition when de-sodiumized, and have poor air stability. Therefore, there is an urgent need to find a high-capacity, high-rate, and structurally stable sodium-electrolyte layered oxide material that can suppress the prominent problems caused by phase transition in the high-voltage region and the sodium-poor phase. Summary of the invention

[0005] In order to solve the above problems, the present invention provides a sodium electrode layered oxide positive electrode material and a preparation method and application thereof.

[0006] In a first aspect, the present invention provides a sodium-based layered oxide positive electrode material, wherein the chemical formula of the sodium-based layered oxide positive electrode material is Na 0.84 Li 0.1 Ni 0.27 Mn a Ti b O2; among them, 0.50≤a≤0.54, 0.09≤b≤0.13.

[0007] Furthermore, the chemical formula of the sodium layered oxide positive electrode material is Na 0.84 Li 0.1 Ni 0.27 Mn 0.54 Ti 0.09 O2.

[0008] Furthermore, the chemical formula of the sodium layered oxide positive electrode material is Na 0.84 Li 0.1 Ni 0.27 Mn 0.52 Ti 0.11 O2.

[0009] Furthermore, the chemical formula of the sodium-phase layered oxide positive electrode material is Na 0.84 Li 0.1 Ni 0.27 Mn 0.5 Ti 0.13 O2.

[0010] Furthermore, the discharge specific capacities of the sodium-based layered oxide positive electrode material in the voltage range of 2.0-4.2V and at a rate of 0.1C are 114.53mAh / g, 120.12mAh / g and 124.32mAh / g, respectively; the discharge specific capacities of the sodium-based layered oxide positive electrode material in the voltage range of 2.0-4.2V and at a rate of 1C are 107.31mAh / g, 112.16mAh / g and 114.93mAh / g, respectively.

[0011] In a second aspect, the present invention provides a method for preparing the sodium layered oxide positive electrode material according to any one of the first aspects, the preparation method comprising the following steps:

[0012] Mixing a Na-containing precursor, a Li-containing precursor, a Ni-containing precursor, a Mn-containing precursor, and a Ti-containing precursor according to a stoichiometric ratio to obtain a precursor mixture;

[0013] The precursor mixture is tableted and then first sintered to obtain an intermediate material;

[0014] The intermediate material is ground, and then subjected to a second sintering at a temperature lower than the first sintering temperature to obtain the sodium-electrolyte layered oxide positive electrode material.

[0015] Further, the Na-containing precursor includes at least one of Na carbonate, Na oxide, Na hydroxide, Na oxalate and Na nitrate, preferably Na2CO3; the Li-containing precursor includes at least one of Li carbonate, Li oxide, Li hydroxide, Li oxalate and Li nitrate, preferably Li2CO3; the Ni-containing precursor includes at least one of Ni carbonate, Ni oxide, Ni hydroxide, Ni oxalate and Ni nitrate, preferably NiO; the Mn-containing precursor includes at least one of Mn carbonate, Mn oxide, Mn hydroxide, Mn oxalate and Mn nitrate, preferably MnO; the Ti-containing precursor includes at least one of Ti carbonate, Ti oxide, Ti hydroxide, Ti oxalate and Ti nitrate, preferably TiO2.

[0016] Furthermore, the working condition parameters of the tabletting include: a pressure of 8 to 15 MPa and a time of 0.5 to 2 minutes; the working condition parameters of the first sintering include: heating from room temperature to 900-1000°C at a heating rate of 5°C / min in an air atmosphere and keeping warm for 15-20 hours, and then naturally cooling to room temperature; the mixing method includes ball milling; the working condition parameters of the ball milling include: using a wet ball milling working method, the ball milling medium is agate ball stone, the dispersant is anhydrous ethanol, the ball milling speed is 300-400r / min when ball milling is used for mixing, the ball milling time is 4-6h, the drying temperature after ball milling is 80-100°C, and the drying time is 4-8h.

[0017] Furthermore, the working condition parameters of the second sintering include: heating from room temperature to 400-800° C. at a heating rate of 2° C. / min in an air atmosphere and keeping the temperature for 5-8 hours, and then naturally cooling to room temperature.

[0018] In a third aspect, the present invention provides the use of the sodium-ion layered oxide positive electrode material described in any one of the first aspects or the sodium-ion layered oxide positive electrode material prepared by the preparation method of the sodium-ion layered oxide positive electrode material described in any one of the second aspects in the preparation of sodium-ion secondary batteries.

[0019] The above technical solution provided by the embodiment of the present invention has at least the following advantages compared with the prior art:

[0020] The embodiment of the present invention provides a sodium layered oxide positive electrode material and a preparation method thereof. The present invention adjusts the sodium content ratio and elemental composition in the positive electrode material by adding a suitable ratio of transition metals to obtain a sodium layered oxide positive electrode material, which effectively improves the structural stability of the material during the cycle and the charge and discharge capacity under high pressure; secondly, through the optimization of the sintering process, the secondary sintering process reduces the alkali content on the surface of the material and adjusts the microscopic morphology of the material, further improving the overall performance of the material, thereby making up for the shortcomings of the prior art. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention.

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0023] Figure 1 A schematic flow chart of a method for preparing a sodium-electrolyte layered oxide positive electrode material provided in an embodiment of the present invention.

[0024] Figure 2 This is a microscopic morphology of a sodium layered oxide positive electrode material provided in Example 1 of the present invention.

[0025] Figure 3 A microscopic morphology of a sodium layered oxide positive electrode material provided in Example 2 of the present invention.

[0026] Figure 4 This is a microscopic morphology of a sodium layered oxide positive electrode material provided in Example 3 of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0029] In a first aspect, the present invention provides a sodium-based layered oxide positive electrode material, wherein the chemical formula of the sodium-based layered oxide positive electrode material is Na 0.84 Li 0.1 Ni 0.27 Mn a Ti b O2; among them, 0.50≤a≤0.54, 0.09≤b≤0.13.

[0030] An embodiment of the present invention provides a sodium layered oxide positive electrode material. The present invention obtains a sodium layered oxide positive electrode material by adding a suitable ratio of transition metals to control the sodium content ratio and elemental composition in the positive electrode material, thereby effectively improving the structural stability of the material during the cycle and the charge and discharge capacity under high voltage.

[0031] Furthermore, the chemical formula of the sodium layered oxide positive electrode material is Na 0.84 Li 0.1 Ni 0.27 Mn 0.54 Ti 0.09 O2.

[0032] In some specific embodiments, the chemical formula of the sodium layered oxide positive electrode material is Na 0.84 Li 0.1 Ni 0.27 Mn 0.52 Ti 0.11 O2.

[0033] In some specific embodiments, the chemical formula of the sodium layered oxide positive electrode material is Na 0.84 Li 0.1 Ni 0.27 Mn 0.5 Ti 0.13 O2.

[0034] In some specific embodiments, the discharge specific capacity of the sodium-based layered oxide positive electrode material in the voltage range of 2.0-4.2V and at a rate of 0.1C is 114.53mAh / g, 120.12mAh / g and 124.32mAh / g, respectively; the discharge specific capacity of the sodium-based layered oxide positive electrode material in the voltage range of 2.0-4.2V and at a rate of 1C is 107.31mAh / g, 112.16mAh / g and 114.93mAh / g, respectively.

[0035] In a second aspect, the present invention provides a method for preparing the sodium layered oxide positive electrode material according to any one of the first aspects, such as Figure 1 As shown, the preparation method comprises the following steps:

[0036] Mixing a Na-containing precursor, a Li-containing precursor, a Ni-containing precursor, a Mn-containing precursor, and a Ti-containing precursor according to a stoichiometric ratio to obtain a precursor mixture;

[0037] The precursor mixture is tableted and then first sintered to obtain an intermediate material;

[0038] The intermediate material is ground, and then subjected to a second sintering at a temperature lower than the first sintering temperature to obtain the sodium-electrolyte layered oxide positive electrode material.

[0039] The present invention is Na 0.84 Li 0.1 Ni 0.27 Mn a Ti b O2; among them, based on the specific element composition design of 0.50≤a≤0.54, 0.09≤b≤0.13, the overall performance of the material is further improved by optimizing the sintering process and reducing the alkali content on the surface of the material and regulating the micromorphology of the material through the secondary sintering process.

[0040] In some specific embodiments, the precursor of the high temperature volatile compound may be appropriately excessive, but the weighed amount of each precursor does not exceed 105% of the theoretical value calculated according to the stoichiometric ratio in the chemical formula, such as the excess ratio of sodium carbonate is 1.03-1.05.

[0041] In some specific embodiments, the Na-containing precursor includes at least one of Na carbonate, Na oxide, Na hydroxide, Na oxalate and Na nitrate, preferably Na2CO3; the Li-containing precursor includes at least one of Li carbonate, Li oxide, Li hydroxide, Li oxalate and Li nitrate, preferably Li2CO3; the Ni-containing precursor includes at least one of Ni carbonate, Ni oxide, Ni hydroxide, Ni oxalate and Ni nitrate, preferably NiO; the Mn-containing precursor includes at least one of Mn carbonate, Mn oxide, Mn hydroxide, Mn oxalate and Mn nitrate, preferably MnO; the Ti-containing precursor includes at least one of Ti carbonate, Ti oxide, Ti hydroxide, Ti oxalate and Ti nitrate, preferably TiO2.

[0042] In some specific embodiments, the working condition parameters of the tabletting include: a pressure of 8 to 15 MPa and a time of 0.5 to 2 minutes; the working condition parameters of the first sintering include: heating from room temperature to 900-1000°C at a heating rate of 5°C / min in an air atmosphere and keeping warm for 15-20 hours, and then naturally cooling to room temperature; the mixing method includes ball milling; the working condition parameters of the ball milling include: using a wet ball milling working method, the ball milling medium is agate ball stone, the dispersant is anhydrous ethanol, the ball milling speed is 300-400r / min when ball milling is used for mixing, the ball milling time is 4-6h, the drying temperature after ball milling is 80-100°C, and the drying time is 4-8h.

[0043] In some specific embodiments, the working condition parameters of the second sintering include: heating from room temperature to 400-800° C. at a heating rate of 2° C. / min in an air atmosphere and keeping the temperature for 5-8 hours, and then naturally cooling to room temperature.

[0044] In a third aspect, the present invention provides the use of the sodium-ion layered oxide positive electrode material described in any one of the first aspects or the sodium-ion layered oxide positive electrode material prepared by the preparation method of the sodium-ion layered oxide positive electrode material described in any one of the second aspects in the preparation of sodium-ion secondary batteries.

[0045] It should be noted that the raw material components involved in the sodium layered oxide positive electrode material and its preparation method and application provided in the embodiments of the present invention, unless otherwise specified or described in detail, can be directly purchased from the market or made in-house according to existing preparation methods; at the same time, the operating steps involved in the preparation method, unless otherwise specified or described in detail, can be carried out according to existing sodium layered oxide positive electrode material preparation methods or using existing equipment, and the present invention document will not repeat them any more.

[0046] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are intended only to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples that do not specify specific conditions are usually measured according to national standards. If there is no corresponding national standard, then the conditions recommended by the manufacturer are followed.

[0047] Example 1

[0048] This example provides a sodium-electrode layered oxide positive electrode material, and the preparation method of the sodium-electrode layered oxide positive electrode material comprises the following steps:

[0049] Step (1): 2.337 g Na2CO3, 1.008 g NiO, 1.915 g MnO, 0.194 g Li2CO3 and 0.359 g TiO2 are ball-milled in a stoichiometric ratio, the ball-milling medium is agate ball stone, the dispersant is anhydrous ethanol, the material-ball ratio is 1:2, and the amount of anhydrous ethanol added is 6 ml, to obtain a uniformly mixed precursor powder;

[0050] Step (2): weighing the precursor powder according to 1 g and pressing it into a tablet (12 mm) at a pressure of 10 MPa and maintaining the pressure for 1 minute to obtain a tablet material;

[0051] Step (3): sintering the tablet material obtained in step (2) at a heating rate of 5°C / min from room temperature to 950°C for 15 hours under air, and naturally cooling to room temperature; then crushing and grinding the tablet material into a powdery material;

[0052] Step (4): The powdered material of step (3) is subjected to secondary sintering at a temperature lower than the primary sintering temperature, and the temperature is raised from room temperature to 750°C at a heating rate of 2°C / min in an air atmosphere and kept at this temperature for 6 hours, and then naturally cooled to room temperature, to obtain the final material, the chemical formula of which is Na 0.84 Li 0.1 Ni 0.27 Mn 0.54 Ti 0.09 O2.

[0053] The chemical formula of the sodium layered oxide positive electrode material obtained in this example is Na 0.84 Li 0.1 Ni 0.27 Mn 0.54 Ti 0.09 O2, denoted as Na 0.84 Li 0.1 Ni 0.27 Mn 0.54 Ti 0.09 O2-1.

[0054] Example 2

[0055] This example provides a sodium layered oxide positive electrode material and a preparation method thereof, which differs from Example 1 only in that the amounts of the precursors in step (1) are adjusted to 2.337 g Na2CO3, 1.008 g NiO, 1.844 g MnO, 0.194 g Li2CO3 and 0.439 g TiO2; the remaining steps and parameters are the same.

[0056] The chemical formula of the sodium layered oxide positive electrode material obtained in this example is Na 0.84 Li 0.1 Ni 0.27 Mn 0.52 Ti0.11 O2.

[0057] Example 3

[0058] This example provides a sodium layered oxide positive electrode material and a preparation method thereof, which differs from Example 1 only in that the amounts of the precursors in step (1) are adjusted to 2.337 g Na2CO3, 1.008 g NiO, 1.773 g MnO, 0.194 g Li2CO3 and 0.519 g TiO2; the remaining steps and parameters are the same.

[0059] The chemical formula of the sodium layered oxide positive electrode material obtained in this example is Na 0.84 Li 0.1 Ni 0.27 Mn 0.5 Ti 0.13 O2.

[0060] Comparative Example 1

[0061] This example provides a sodium layered oxide positive electrode material and a preparation method thereof, which differs from Example 1 only in that: 1) the precursors in step (1) are adjusted to 2.337 g Na2CO3, 1.008 g NiO, 2.234 g MnO and 0.194 g Li2CO3 to obtain a sodium layered oxide positive electrode material with a chemical formula of Na 0.84 Li 0.1 Ni 0.27 Mn 0.63 O2 sodium layered oxide positive electrode material; 2) the secondary sintering in step (4) is not performed; the remaining steps and parameters are the same.

[0062] The chemical formula of the sodium layered oxide positive electrode material obtained in this example is Na 0.84 Li 0.1 Ni 0.27 Mn 0.63 O2, denoted as Na 0.84 Li 0.1 Ni 0.27 Mn 0.63 O2-1.

[0063] Comparative Example 2

[0064] This example provides a sodium layered oxide positive electrode material and a preparation method thereof, which is different from Example 1 only in that the secondary sintering in step (4) is not performed; the remaining steps and parameters are the same.

[0065] The chemical formula of the sodium layered oxide positive electrode material obtained in this example is Na 0.84 Li 0.1 Ni 0.27 Mn 0.54 Ti 0.09O2, denoted as Na 0.84 Li 0.1 Ni 0.27 Mn 0.54 Ti 0.09 O2-2.

[0066] Comparative Example 3

[0067] This example provides a sodium layered oxide positive electrode material and a preparation method thereof, which is different from Example 1 in that the precursors in step (1) are adjusted to 2.337 g Na2CO3, 1.008 g NiO, 2.234 g MnO and 0.194 g Li2CO3 to obtain a sodium layered oxide positive electrode material with a chemical formula of Na 0.84 Li 0.1 Ni 0.27 Mn 0.63 The sodium layered oxide positive electrode material of O2; the remaining steps and parameters are the same.

[0068] The chemical formula of the sodium layered oxide positive electrode material obtained in this example is Na 0.84 Li 0.1 Ni 0.27 Mn 0.63 O2, denoted as Na 0.84 Li 0.1 Ni 0.27 Mn 0.63 O2-2.

[0069] Comparative Example 4

[0070] This example provides a sodium layered oxide positive electrode material and a preparation method thereof, which is different from Example 1 in that the precursors in step (1) are adjusted to 2.337 g Na2CO3, 1.008 g NiO, 2.128 g MnO, 0.194 g Li2CO3 and 0.120 g TiO2 to obtain a sodium layered oxide positive electrode material with a chemical formula of Na 0.84 Li 0.1 Ni 0.27 Mn 0.6 Ti 0.03 The sodium layered oxide positive electrode material of O2; the remaining steps and parameters are the same.

[0071] The chemical formula of the sodium layered oxide positive electrode material obtained in this example is Na 0.84 Li 0.1 Ni 0.27 Mn 0.6 Ti 0.03 O2.

[0072] Comparative Example 5

[0073] This example provides a sodium layered oxide positive electrode material and a preparation method thereof, which differs from Example 1 only in that the temperature of the first sintering in step (3) is adjusted to 750°C and the time is 6 hours, and the temperature of the second sintering in step (4) is adjusted to 950°C and the time is 15 hours; the remaining steps and parameters are the same.

[0074] The chemical formula of the sodium layered oxide positive electrode material obtained in this example is Na 0.84 Li 0.1 Ni 0.27 Mn 0.54 Ti 0.09 O2, denoted as Na 0.84 Li 0.1 Ni 0.27 Mn 0.54 Ti 0.09 O2-3.

[0075] Test Case

[0076] In this example, the sodium layered oxide positive electrode material obtained in the above embodiments and comparative examples is mixed with conductive carbon black (SuperP) and polyvinylidene fluoride (PVDF) glue, and an appropriate amount of N-methylpyrrolidone (NMP) solution is added as a mixing medium, and ball milling is performed to prepare a slurry (mixing ratio 7:2:1); the slurry is evenly coated on the surface of the aluminum foil using a scraper, and after drying in a blast oven for 1 hour, it is transferred into a vacuum drying oven and dried for 12 hours, and the dried aluminum foil is cut into 1 cm diameter discs as positive electrode sheets, and button batteries are assembled in a vacuum glove box for electrochemical performance testing. The test condition parameters include: the test voltage range is 2-4.2V (1C=150mAh / g); the test results are shown in Table 1.

[0077] Table 1

[0078] Cathode Materials Charging capacity (0.1C) Discharge specific capacity (0.1C) First effect Discharge capacity (1C) Example 1 124.05mAh / g 114.53mAh / g 92.33％ 107.31mAh / g Example 2 126.93mAh / g 120.12mAh / g 94.64％ 112.16mAh / g Example 3 131.98mAh / g 124.32mAh / g 94.20％ 114.93mAh / g Comparative Example 1 102.31mAh / g 90.94mAh / g 88.89％ 86.05mAh / g Comparative Example 2 116.04mAh / g 108.80mAh / g 93.76％ 103.39mAh / g Comparative Example 3 106.77mAh / g 99.23mAh / g 92.94％ 93.86mAh / g Comparative Example 4 111.83mAh / g 102.72mAh / g 91.86％ 98.68mAh / g Comparative Example 5 118.16mAh / g 109.86mAh / g 92.98％ 104.21mAh / g

[0079] From Table 1, we can see that:

[0080] 1) It can be seen from the test results of Example 1, Example 2 and Example 3 that by controlling the Mn / Ti content ratio, the discharge specific capacity and the first efficiency of the sodium-based layered oxide positive electrode material are significantly increased compared with the control group. Through the second calcination process, part of the surface residual alkali enters the bulk phase, which significantly reduces the surface alkali content of the material and further increases the charge and discharge capacity; and when the Mn / Ti content ratio is controlled to be that of Example 3, the performance of the obtained sodium-based layered oxide positive electrode material is the best.

[0081] 2) It can be seen from the test results of Comparative Example 1, Comparative Example 2, Comparative Example 3 and Example 1 that the present invention optimizes the sintering process based on the chemical formula designed on the basis of specific element composition, and the synergistic effect of the two is significant, which achieves a significant improvement in the performance of the sodium-based layered oxide positive electrode material and achieves a synergistic effect of "1+1>2".

[0082] 3) It can be seen from the test results of Comparative Examples 4 and 5 and Example 1 that when the Ti / Mn ratio in the chemical formula of the sodium-electrode layered oxide positive electrode material in the present invention is inappropriate or the sintering temperature is adjusted twice, the performance of the obtained sodium-electrode layered oxide positive electrode material will be significantly reduced.

[0083] In addition, the microscopic morphology of the sodium layered oxide positive electrode materials obtained in Examples 1, 2 and 3 of the present invention are shown in FIG. Figure 2 , Figure 3 and Figure 4 shown.

[0084] Various embodiments of the present invention may be presented in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity, and should not be understood as a rigid limitation on the scope of the present invention; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numerical values ​​within the range. For example, the range description from 1 to 6 should be considered to have specifically disclosed sub-ranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5 and 6, which apply regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0085] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A sodium layered oxide positive electrode material, characterized in that: The chemical formula of the sodium layered oxide positive electrode material is Na 0.84 Li 0.1 Ni 0.27 Mn a Ti b O2; among them, 0.50≤a≤0.54, 0.09≤b≤0.

13.

2. The sodium layered oxide positive electrode material according to claim 1, characterized in that: The chemical formula of the sodium layered oxide positive electrode material is Na 0.84 Li 0.1 Ni 0.27 Mn 0.54 Ti 0.09 O2.

3. The method for preparing the sodium layered oxide positive electrode material according to claim 1, characterized in that: The chemical formula of the sodium layered oxide positive electrode material is Na 0.84 Li 0.1 Ni 0.27 Mn 0.52 Ti 0.11 O2.

4. The method for preparing the sodium layered oxide positive electrode material according to claim 1, characterized in that: The chemical formula of the sodium layered oxide positive electrode material is Na 0.84 Li 0.1 Ni 0.27 Mn 0.5 Ti 0.13 O2.

5. The sodium layered oxide positive electrode material according to any one of claims 1 to 4, characterized in that: The discharge specific capacities of the sodium-based layered oxide positive electrode material at a voltage range of 2.0-4.2V and a rate of 0.1C are 114.53mAh / g, 120.12mAh / g and 124.32mAh / g, respectively; the discharge specific capacities of the sodium-based layered oxide positive electrode material at a voltage range of 2.0-4.2V and a rate of 1C are 107.31mAh / g, 112.16mAh / g and 114.93mAh / g, respectively.

6. A method for preparing a sodium layered oxide positive electrode material according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: Mixing a Na-containing precursor, a Li-containing precursor, a Ni-containing precursor, a Mn-containing precursor, and a Ti-containing precursor according to a stoichiometric ratio to obtain a precursor mixture; The precursor mixture is tableted and then first sintered to obtain an intermediate material; The intermediate material is ground and then subjected to a second sintering at a temperature lower than the first sintering temperature to obtain the sodium-electrolyte layered oxide positive electrode material.

7. The method for preparing the sodium layered oxide positive electrode material according to claim 6, characterized in that: The Na-containing precursor includes at least one of Na carbonate, Na oxide, Na hydroxide, Na oxalate and Na nitrate; the Li-containing precursor includes at least one of Li carbonate, Li oxide, Li hydroxide, Li oxalate and Li nitrate; the Ni-containing precursor includes at least one of Ni carbonate, Ni oxide, Ni hydroxide, Ni oxalate and Ni nitrate; the Mn-containing precursor includes at least one of Mn carbonate, Mn oxide, Mn hydroxide, Mn oxalate and Mn nitrate; and the Ti-containing precursor includes at least one of Ti carbonate, Ti oxide, Ti hydroxide, Ti oxalate and Ti nitrate.

8. The method for preparing the sodium layered oxide positive electrode material according to claim 6, characterized in that: The working condition parameters of the tabletting include: a pressure of 8 to 15 MPa and a time of 0.5 to 2 minutes; the working condition parameters of the first sintering include: heating from room temperature to 900-1000°C at a heating rate of 5°C / min in an air atmosphere and keeping warm for 15-20 hours, and then naturally cooling to room temperature; the mixing method includes ball milling; the working condition parameters of the ball milling include: using a wet ball milling working method, the ball milling medium is agate ball stone, the dispersant is anhydrous ethanol, the ball milling speed is 300-400r / min when ball milling is used for mixing, the ball milling time is 4-6h, the drying temperature after ball milling is 80-100°C, and the drying time is 4-8h.

9. The method for preparing a sodium-electrolyte layered oxide positive electrode material according to claim 6, characterized in that: The working condition parameters of the second sintering include: heating from room temperature to 400-800° C. at a heating rate of 2° C. / min in an air atmosphere and keeping the temperature for 5-8 hours, and then naturally cooling to room temperature.

10. Use of the sodium-ion layered oxide positive electrode material according to any one of claims 1 to 5 or the sodium-ion layered oxide positive electrode material prepared by the method for preparing the sodium-ion layered oxide positive electrode material according to any one of claims 6 to 9 in preparing a sodium-ion secondary battery.

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