A high-voltage O3-phase sodium-ion battery cathode material and a preparation method thereof

Abstract

The present invention discloses an O3 phase sodium ion battery positive electrode material and a preparation method thereof, wherein the chemical formula is: NaNi 1 / 3‑x Fe 1 / 3‑ y Mn 1 / 3‑z Li x Co y Ti z O2; wherein 0≤x<1 / 3, 0≤y<1 / 3, 0≤z<1 / 3, and electrical neutrality is satisfied. The O3 phase sodium ion battery positive electrode material of the present invention, by replacing part of (Ni, Fe, Mn) with Li, Co, and Ti, can not only effectively improve the electronic conductivity of the sodium ion battery positive electrode material and enhance the fast charging capability of the sodium ion battery, but also significantly improve the structural stability and cycle stability of the positive electrode material, especially at high voltage; the O3 phase sodium ion battery positive electrode material of the present invention has the advantages of high specific capacity, good rate performance, and good cycle stability.

Description

Technical Field

[0001] The present invention relates to an O3 phase sodium ion battery positive electrode material suitable for high voltage, and also relates to a preparation method of the O3 phase sodium ion battery positive electrode material. Background Art

[0002] Emerging electrochemical energy storage technologies have become a research hotspot due to their high efficiency, environmental friendliness, and wide applicability. Lithium-ion batteries, with their high energy density and long cycle life, have become a popular choice for advanced energy storage systems. However, lithium deposits in the Earth's crust are scarce and unevenly distributed. Rising lithium prices have severely hampered the development of the lithium-ion battery market. Sodium and lithium share similar physical and chemical properties, and the development of sodium-ion batteries, which use sodium instead of lithium, has garnered widespread attention worldwide.

[0003] From the perspective of the charge and discharge principles of sodium-ion batteries, the development of high-performance electrode materials is clearly essential. The structure and function of electrode materials are crucial to the electrochemical performance of sodium-ion batteries. Among them, the cathode plays an important role in determining sodium kinetics, reversibility, energy density, and cycle life. Voltage and specific capacity are directly related to the key parameters of sodium-ion batteries. The focus of sodium-ion battery research has shifted to the development of new cathode materials and improving the performance of current cathode materials. O3-phase transition metal oxides are widely considered to be the most promising cathode candidate materials due to their excellent performance in terms of synthesis methods, cost-effectiveness, and electrochemical performance. However, under high voltage, O3-type sodium-ion battery cathode materials are prone to drastic volume changes, causing irreversible damage to the structure, which in turn hinders the release of their capacity, resulting in poor rate performance and cycling stability. Summary of the Invention

[0004] Purpose of the invention: The purpose of the present invention is to provide an O3 phase sodium ion battery positive electrode material suitable for high voltage, the O3 phase sodium ion battery positive electrode material has high specific capacity, good rate performance, and can still maintain good structural stability and cycle stability under high voltage conditions; another purpose of the present invention is to provide a preparation method of the above-mentioned O3 phase sodium ion battery positive electrode material.

[0005] Technical solution: The O3 phase sodium ion battery positive electrode material of the present invention has the chemical formula: NaNi 1 / 3-x Fe 1 / 3- y Mn 1 / 3-z Li x Co y Ti z O2; where 0≤x<1 / 3, 0≤y<1 / 3, 0≤z<1 / 3, and electrical neutrality is satisfied.

[0006] Furthermore, 0≤x≤0.2, 0≤y≤0.1, 0≤z≤0.1, and electrical neutrality is satisfied.

[0007] The preparation method of the above-mentioned O3 phase sodium ion battery positive electrode material comprises the following steps:

[0008] (1) Weighing the corresponding sodium source, nickel source, iron source, manganese source, lithium source, cobalt source and titanium source according to the formula, mixing the sodium source, nickel source, iron source, manganese source, lithium source, cobalt source, titanium source and citric acid, performing a sol-gel reaction, and drying after the reaction to obtain a precursor;

[0009] (2) The precursor is ball-milled and solid-phase sintered to obtain an O3 phase sodium ion battery positive electrode material.

[0010] Wherein, in step (1), the sodium source is one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium acetate or sodium nitrate; the nickel source is one or more of nickel acetate, nickel nitrate or nickel sulfate; the iron source is one or more of ferric acetate, ferric nitrate, ferrous oxide, ferrous chloride, ferrous oxide or ferric oxide; the manganese source is one or more of manganese acetate, manganese chloride or manganese sulfate; the lithium source is one or more of lithium carbonate, lithium acetate, lithium nitrate or lithium sulfate; the cobalt source is one or more of cobalt carbonate, cobalt acetate or cobalt sulfate; the titanium source is one or more of titanium dioxide, titanium chloride or titanium sulfate.

[0011] Wherein, in step (1), the molar ratio of the transition metal source to the sodium source is 1:1.01-1.10, and the excess sodium source is used to compensate for the volatilization of sodium during solid-phase sintering.

[0012] Wherein, in step (1), the sol-gel reaction is specifically as follows: dissolving a sodium source, a nickel source, an iron source, a manganese source, a lithium source and a cobalt source in deionized water to form a solution A; dissolving a titanium source and citric acid in deionized water to form a solution B, and adding the solution B to the solution A to carry out a sol-gel reaction; the reaction temperature is 60 to 90° C.; and the reaction time is 2 to 6 hours.

[0013] The stirring speed during the reaction is 500 to 2000 r / min.

[0014] Wherein, in step (2), the ball-to-material ratio during ball milling of the precursor is 1:2 to 1:10; the ball milling speed is 100 to 600 r / min, and the ball milling time is 1 to 6 h.

[0015] Among them, in step (2), the solid-phase sintering adopts stage sintering, specifically: first heating to the first stage insulation temperature of 300-500°C, keeping warm for 1-5 hours, and the heating rate is 1-8°C / min; then heating to the second stage insulation temperature of 600-700°C, keeping warm for 1-5 hours, and the heating rate is 1-8°C / min; finally heating to the sintering temperature of 850-950°C, and keeping warm for 8-20 hours.

[0016] The solid phase sintering is carried out in an oxygen or air atmosphere.

[0017] In the O3 phase sodium ion battery positive electrode material of the present invention, the introduction of Li ions can promote the deintercalation of more sodium ions, increase the specific capacity of the positive electrode material, improve the energy density of the battery, and optimize the lattice structure of the material, thereby improving the charge and discharge rate and cycle stability of the battery; Ti substitution can effectively enhance the binding between transition metals and oxygen by increasing the oxygen electron density, effectively inhibiting the irreversible phase change and alleviating the structural change of the electrode material, thereby reducing Na + The energy barrier for migration helps sodium maintain faster intercalation and deintercalation capabilities; the addition of Co ions can provide partial capacity, significantly improving the battery's discharge platform and suppressing the decay of the discharge median voltage. The O3-phase sodium-ion battery cathode material of the present invention, through multi-component co-substitution, can make the variable valence ions originally uniformly distributed throughout the overall structure more prone to disorder, thereby suppressing the phase transition caused by the valence change of metal ions, reducing the energy of the entire system, and improving the structural stability of the electrode material during cycling under high-voltage conditions.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0019] (1) The O3 phase sodium ion battery positive electrode material of the present invention, by using Li, Co, and Ti to replace part of (Ni, Fe, and Mn), can not only effectively improve the electronic conductivity of the sodium ion battery positive electrode material and enhance the fast charging capability of the sodium ion battery, but also significantly improve the structural stability and cycle stability of the positive electrode material, especially at high voltage; the O3 phase sodium ion battery positive electrode material of the present invention also has the advantages of high specific capacity, good rate performance, and good cycle stability;

[0020] (2) The method of the present invention adopts the sol-gel method in the precursor preparation stage, and the wet substitution makes the substitution elements evenly distributed in the positive electrode material, thereby improving the structural stability of the final positive electrode material; at the same time, the ball milling method and the solid phase sintering method are combined, wherein the ball milling method can make the precursor fully mixed, which is conducive to a more complete and uniform reaction between the precursor mixture particles during the subsequent heat treatment; the solid phase sintering method forms a highly stable sodium ion battery positive electrode material with a more complete and uniform physical phase through programmed heating and segmented insulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is the XRD spectrum of Comparative Example 1;

[0022] Figure 2 This is a charge and discharge curve diagram of the button battery of Comparative Example 1;

[0023] Figure 3 This is a cycle curve diagram of the button battery of Comparative Example 1;

[0024] Figure 4 is the XRD spectrum of Example 1;

[0025] Figure 5 The charge and discharge curves of the button batteries of Comparative Example 1 and Examples 1 to 3 are shown;

[0026] Figure 6 The charge and discharge curves of the button batteries of Comparative Example 1 and Examples 4-5 are shown;

[0027] Figure 7 The cycle curves of button batteries of Comparative Example 1 and Examples 1 to 3 are shown;

[0028] Figure 8 The cycle curves of button batteries of Comparative Example 1 and Examples 4-5 are shown;

[0029] Figure 9 The figure is a rate performance curve diagram of button batteries of comparative example 1 and embodiments 1 to 3;

[0030] Figure 10 It is a rate performance curve diagram of button batteries of comparative example 1 and embodiments 4-5. DETAILED DESCRIPTION

[0031] Example 1

[0032] The method for preparing the positive electrode material of an O3 phase sodium ion battery of the present invention comprises the following steps:

[0033] (1) 1.7220 g of sodium acetate (5% excess), 1.6591 g of nickel acetate, 1.3267 g of ferric acetate, 1.1438 g of manganese acetate, and 0.4982 g of cobalt acetate were dissolved in 100 mL of deionized water to form solution A; 0.1597 g of titanium dioxide and 5.7630 g of citric acid were dissolved in 50 mL of deionized water and dissolved until completely dissolved to form solution B; solution B was added to solution A, stirred at 800 rpm in an 80°C water bath for 3 h, and then transferred to a 120°C oven for drying and storage for 12 h to obtain a precursor;

[0034] (2) The precursor was placed in a ball mill, the ball-to-material ratio was controlled to be 1:5, the ball mill speed was set to 300 r / min, and the ball mill was alternately rotated forward and reverse for 3 h. After ball milling, the sample was collected and spread flat on a porcelain boat, transferred to a muffle furnace, and solid-phase sintered in an air atmosphere; first, the temperature was raised to the first stage holding temperature of 500 ° C, kept warm for 2 h, and the heating rate was 3 ° C / min; then the temperature was raised to the second stage holding temperature of 680 ° C, kept warm for 2 h, and the heating rate was 3 ° C / min; finally, the temperature was raised to the sintering temperature of 900 ° C and sintered for 12 h; after natural cooling, the sample was passed through a 200 mesh sieve to obtain the O3 phase sodium ion battery positive electrode material.

[0035] The prepared NaNi 0.33 Fe 0.23 Mn 0.23 Ti 0.1 Co 0.1 O2 for phase analysis, Figure 4 It can be seen from the XRD spectrum that after doping with metal ions, the main structure of the material is still O3 type structure, and the crystal structure of the original positive electrode material is not destroyed.

[0036] The prepared NaNi 0.33 Fe 0.23 Mn 0.23 Ti 0.1 Co 0.1 O2 was assembled into button cells and cycle performance was tested at 2.0-4.2V and 1C (1C=150mA / g). Figure 5 and Figure 7 The test results show that the initial discharge capacity at a current density of 0.1C is 156.1mAh / g, and the discharge capacity of the battery after 200 cycles is 46.8mAh / g, with a capacity retention rate of 33.66%.

[0037] Example 2

[0038] The method for preparing the positive electrode material of an O3 phase sodium ion battery of the present invention comprises the following steps:

[0039] (1) 1.7220 g of sodium acetate (5% excess), 1.4102 g of nickel acetate, 0.9287 g of ferric acetate, 1.1438 g of manganese acetate, 0.066 g of lithium acetate, and 0.4982 g of cobalt acetate were dissolved in 100 mL of deionized water to form solution A; 0.1597 g of titanium dioxide and 5.7630 g of citric acid were dissolved in 50 mL of deionized water and dissolved until completely dissolved to form solution B; solution B was added to solution A, stirred at a stirring rate of 800 r / min in an 80°C water bath for 3 h, and then transferred to a 120°C oven for drying and storage for 12 h to obtain a precursor;

[0040] (2) The precursor was placed in a ball mill, the ball-to-material ratio was controlled to be 1:5, the ball mill speed was set to 300 r / min, and the ball mill was alternately rotated forward and reverse for 3 h. After ball milling, the sample was collected and spread flat on a porcelain boat, transferred to a muffle furnace, and solid-phase sintered in an air atmosphere; first, the temperature was raised to the first stage holding temperature of 500 ° C, kept warm for 2 h, and the heating rate was 3 ° C / min; then the temperature was raised to the second stage holding temperature of 680 ° C, kept warm for 2 h, and the heating rate was 3 ° C / min; finally, the temperature was raised to the sintering temperature of 900 ° C and sintered for 12 h; after natural cooling, the sample was passed through a 200 mesh sieve to obtain the O3 phase sodium ion battery positive electrode material.

[0041] The prepared NaNi 0.28 Fe 0.23 Mn 0.23 Ti 0.1 Co 0.1 Li 0.05 O2 was assembled into button cells and cycle performance was tested at 2.0-4.2V and 1C (1C=150mA / g). Figure 6 and Figure 8 The test results show that the initial discharge capacity at a current density of 0.1C is 161.6mAh / g, and the discharge capacity of the battery after 200 cycles is 59.6mAh / g, with a capacity retention rate of 46.34%.

[0042] Example 3

[0043] The method for preparing the positive electrode material of an O3 phase sodium ion battery of the present invention comprises the following steps:

[0044] (1) 1.7220 g of sodium acetate (5% excess), 1.1613 g of nickel acetate, 0.9287 g of ferric acetate, 1.1438 g of manganese acetate, 0.1320 g of lithium acetate, and 0.4982 g of cobalt acetate were dissolved in 100 mL of deionized water to form solution A; 0.1597 g of titanium dioxide and 5.7630 g of citric acid were dissolved in 50 mL of deionized water and dissolved until completely dissolved to form solution B; solution B was added to solution A, stirred at a stirring rate of 800 r / min in an 80°C water bath for 3 h, and then transferred to a 120°C oven for drying and storage for 12 h to obtain a precursor;

[0045] (2) The precursor was placed in a ball mill, the ball-to-material ratio was controlled to be 1:5, the ball mill speed was set to 300 r / min, and the ball mill was alternately rotated forward and reverse for 3 h. After ball milling, the sample was collected and spread flat on a porcelain boat, transferred to a muffle furnace, and solid-phase sintered in an air atmosphere; first, the temperature was raised to the first stage holding temperature of 500 ° C, kept warm for 2 h, and the heating rate was 3 ° C / min; then the temperature was raised to the second stage holding temperature of 680 ° C, kept warm for 2 h, and the heating rate was 3 ° C / min; finally, the temperature was raised to the sintering temperature of 900 ° C and sintered for 12 h; after natural cooling, the sample was passed through a 200 mesh sieve to obtain the O3 phase sodium ion battery positive electrode material.

[0046] The prepared NaNi 0.23 Fe 0.23 Mn 0.23 Ti 0.1 Co 0.1 Li 0.1 O2 was assembled into button cells and cycle performance was tested at 2.0-4.2V and 1C (1C=150mA / g). Figure 6 and Figure 8 The test results show that the initial discharge capacity at a current density of 0.1C is 163.1mAh / g, and the discharge capacity of the battery after 200 cycles is 81.7mAh / g, with a capacity retention rate of 61.33%.

[0047] Example 4

[0048] The method for preparing the positive electrode material of an O3 phase sodium ion battery of the present invention comprises the following steps:

[0049] (1) 1.7220 g of sodium acetate (5% excess), 0.9125 g of nickel acetate, 0.9287 g of ferric acetate, 1.1438 g of manganese acetate, 0.1980 g of lithium acetate, and 0.4982 g of cobalt acetate were dissolved in 100 mL of deionized water to form solution A; 0.1597 g of titanium dioxide and 5.7630 g of citric acid were dissolved in 50 mL of deionized water and dissolved until they were completely dissolved to form solution B; solution B was added to solution A, stirred at a stirring rate of 800 r / min in an 80°C water bath for 3 h, and then transferred to a 120°C oven for drying and storage for 12 h to obtain a precursor;

[0050] (2) The precursor was placed in a ball mill, the ball-to-material ratio was controlled to be 1:5, the ball mill speed was set to 300 r / min, and the ball mill was alternately rotated forward and reverse for 3 h. After ball milling, the sample was collected and spread flat on a porcelain boat, transferred to a muffle furnace, and solid-phase sintered in an air atmosphere; first, the temperature was raised to the first stage holding temperature of 500 ° C, kept warm for 2 h, and the heating rate was 3 ° C / min; then the temperature was raised to the second stage holding temperature of 680 ° C, kept warm for 2 h, and the heating rate was 3 ° C / min; finally, the temperature was raised to the sintering temperature of 900 ° C and sintered for 12 h; after natural cooling, the sample was passed through a 200 mesh sieve to obtain the O3 phase sodium ion battery positive electrode material.

[0051] The prepared NaNi 0.18 Fe 0.23 Mn 0.23 Ti 0.1 Co 0.1 Li 0.15 O2 was assembled into button cells and cycle performance was tested at 2.0-4.2V and 1C (1C=150mA / g). Figure 6 and Figure 8 The test results show that the initial discharge capacity at a current density of 0.1C is 160.2mAh / g, and the discharge capacity of the battery after 200 cycles is 84.2mAh / g, with a capacity retention rate of 61.28%.

[0052] Example 5

[0053] The method for preparing the positive electrode material of an O3 phase sodium ion battery of the present invention comprises the following steps:

[0054] (1) 1.7220 g of sodium acetate (5% excess), 0.6636 g of nickel acetate, 0.9287 g of ferric acetate, 1.1438 g of manganese acetate, 0.2640 g of lithium acetate, and 0.4982 g of cobalt acetate were dissolved in 100 mL of deionized water to form solution A; 0.1597 g of titanium dioxide and 5.7630 g of citric acid were dissolved in 50 mL of deionized water and dissolved until completely dissolved to form solution B; solution B was added to solution A, stirred at a stirring rate of 800 r / min in an 80°C water bath for 3 h, and then transferred to a 120°C oven for drying and storage for 12 h to obtain a precursor;

[0055] (2) The precursor was placed in a ball mill, the ball-to-material ratio was controlled to be 1:5, the ball mill speed was set to 300 r / min, and the ball mill was alternately rotated forward and reverse for 3 h. After ball milling, the sample was collected and spread flat on a porcelain boat, transferred to a muffle furnace, and solid-phase sintered in an air atmosphere; first, the temperature was raised to the first stage holding temperature of 500 ° C, kept warm for 2 h, and the heating rate was 3 ° C / min; then the temperature was raised to the second stage holding temperature of 680 ° C, kept warm for 2 h, and the heating rate was 3 ° C / min; finally, the temperature was raised to the sintering temperature of 900 ° C and sintered for 12 h; after natural cooling, the sample was passed through a 200 mesh sieve to obtain the O3 phase sodium ion battery positive electrode material.

[0056] The prepared NaNi 0.13 Fe 0.23 Mn 0.23 Ti 0.1 Co 0.1 Li 0.2 O2 was assembled into button cells and cycle performance was tested at 2.0-4.2V and 1C (1C=150mA / g). Figure 6 and Figure 8 The test results show that the initial discharge capacity at a current density of 0.1C is 150.5mAh / g, and the discharge capacity of the battery after 200 cycles is 67.7mAh / g, with a capacity retention rate of 59.43%.

[0057] Comparative Example 1

[0058] A method for preparing an O3 phase sodium ion battery positive electrode material comprises the following steps:

[0059] (1) 1.7220 g of sodium acetate (5% excess), 1.6591 g of nickel acetate, 1.3267 g of ferric acetate, and 1.6339 g of manganese acetate were dissolved in 100 mL of deionized water to form solution A; 5.7630 g of citric acid was dissolved in 50 mL of deionized water and dissolved completely to form solution B; solution B was added to solution A, stirred at 800 rpm in an 80°C water bath for 3 h, and then transferred to a 120°C oven for drying and storage for 12 h to obtain a precursor;

[0060] (2) The precursor was placed in a ball mill, the ball-to-material ratio was controlled to be 1:5, the ball mill speed was set to 300 r / min, and the ball mill was alternately rotated forward and reverse for 3 h. After ball milling, the sample was collected and spread flat on a porcelain boat, transferred to a muffle furnace, and solid-phase sintered in an air atmosphere; first, the temperature was raised to the first stage holding temperature of 500 ° C, kept warm for 2 h, and the heating rate was 3 ° C / min; then the temperature was raised to the second stage holding temperature of 680 ° C, kept warm for 2 h, and the heating rate was 3 ° C / min; finally, the temperature was raised to the sintering temperature of 900 ° C and sintered for 12 h; after natural cooling, the sample was passed through a 200 mesh sieve to obtain the O3 phase sodium ion battery positive electrode material.

[0061] The prepared NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 for phase analysis, Figure 1 It can be seen from the XRD spectrum that the main structure of the material is O3 type structure.

[0062] The prepared NaNi 1 / 3 Fe 1 / 3 Mn 1 / 3 O2 was assembled into button cells and cycle performance was tested at 2.0-4.2V and 1C (1C=150mA / g). Figure 2 and Figure 3 The test results show that the first discharge capacity at a current density of 0.1C is 152.9mAh / g, and the discharge capacity of the battery after 200 cycles is 67.7mAh / g, with a capacity retention rate of only 21.47%.

[0063] The O3-phase sodium-ion battery cathode materials obtained in Comparative Example 1 and Examples 1-5 were tested using 2032-size button cells as a benchmark. The following procedure was used: the cathode material was dried at 120°C for 12 hours and then mixed uniformly with a conductive agent and binder for 4 hours. The mass ratio of positive electrode material: conductive agent: binder was 8:1:1. The prepared slurry was evenly coated on aluminum foil, then dried, pressed, and cut into electrode sheets. A sodium metal sheet served as the counter electrode, and glass fiber served as the separator. A 1 mol / L NaClO4 solution in ethylene carbonate (EC) / propylene carbonate (PC) (volume ratio 1:1) was used as the electrolyte. The button cells were assembled in an argon-filled glove box. The assembled button cells were then subjected to cycling performance testing at 2.0-4.2V.

[0064] From the comparison between Comparative Example 1 and Examples 1 to 5, it can be seen that compared with the unmodified NFM prepared in Comparative Example 1, the button-type batteries prepared in Examples 1 to 5 have smoother charge and discharge curves and more stable structures. From the comparison between Comparative Example 1 and Example 1, it can be seen that when part of the molar amount of Fe and Mn is replaced by Co and Ti elements, the performance of the obtained positive electrode material is significantly improved. At the same time, according to the comparison of Examples 1 to 5, it can be seen that the introduction of appropriate Li elements can further increase the specific capacity of the positive electrode material and improve the rate performance and cycle stability of the battery; while excessive Li will lead to a decrease in battery capacity, such as Figure 9 and Figure 10 shown.

Claims

1. A method for preparing an O3 phase sodium ion battery cathode material, characterized in that: The method comprises the following steps: (1) weighing corresponding sodium source, nickel source, iron source, manganese source, lithium source, cobalt source and titanium source according to the formula amount, mixing the sodium source, nickel source, iron source, manganese source, lithium source, cobalt source, titanium source and citric acid, carrying out a sol-gel reaction, and drying after the reaction to obtain a precursor; (2) ball-milling the precursor and solid-phase sintering it to obtain an O3 phase sodium ion battery positive electrode material; the chemical formula of the obtained O3 phase sodium ion battery positive electrode material is: NaNi 1 / 3-x Fe 1 / 3-y Mn 1 / 3-z Li x Co y Ti z O2; where x=0.15, y=0.1, z=0.1, and electrical neutrality is satisfied.

2. The preparation method according to claim 1, wherein: In step (1), the sodium source is one or more of sodium hydroxide, sodium carbonate, sodium bicarbonate, sodium acetate or sodium nitrate; the nickel source is one or more of nickel acetate, nickel nitrate or nickel sulfate; the iron source is one or more of ferric acetate, ferric nitrate, ferrous oxide, ferrous chloride, ferrous oxide or ferric oxide; the manganese source is one or more of manganese acetate, manganese chloride or manganese sulfate; the lithium source is one or more of lithium carbonate, lithium acetate, lithium nitrate or lithium sulfate; the cobalt source is one or more of cobalt carbonate, cobalt acetate or cobalt sulfate; the titanium source is one or more of titanium dioxide, titanium chloride or titanium sulfate.

3. The preparation method according to claim 1, wherein: In step (1), the sol-gel reaction is specifically as follows: dissolving a sodium source, a nickel source, an iron source, a manganese source, a lithium source and a cobalt source in deionized water to form a solution A; dissolving a titanium source and citric acid in deionized water to form a solution B, and adding the solution B to the solution A to carry out a sol-gel reaction; the reaction temperature is 60-90°C; and the reaction time is 2-6 hours.

4. The preparation method according to claim 3, wherein: The stirring speed during the reaction is 500~2000r / min.

5. The preparation method according to claim 1, wherein: In step (2), the ball-to-material ratio during ball milling of the precursor is 1:2~1:10; the ball milling speed is 100~600r / min, and the ball milling time is 1~6h.

6. The preparation method according to claim 1, wherein: In step (2), the solid-phase sintering adopts stage sintering, specifically: first heating to the first stage insulation temperature of 300~500℃, keeping it warm for 1~5h, and the heating rate is 1~8℃ / min; then heating to the second stage insulation temperature of 600~700℃, keeping it warm for 1~5h, and the heating rate is 1~8℃ / min; finally heating to the sintering temperature of 850~950℃, and keeping it warm for 8~20h.

7. The preparation method according to claim 6, characterized in that: The solid phase sintering is performed in an oxygen or air atmosphere.

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