A cathode material, its preparation method and application

Abstract

The present invention relates to the technical field of electrode materials, and particularly to a cathode material, a preparation method thereof, and an application thereof. The present invention provides a cathode material, comprising an O3 phase and a P3 phase coating layer; the chemical composition of the cathode material is: Na a Li b Ni c Fe d Mn e Ti f O 2+β , where a is 0.9 to 1.0, b is 0.01 to 0.03, c is 0.3 to 0.4, d is 0.3 to 0.4, e is 0.3 to 0.4, f is 0.01 to 0.03, and the value of β satisfies the valence balance; the valence states of Mn in the cathode material include +2 and +3. The cathode material not only has excellent electrochemical performance of the O3 phase cathode, but also has good environmental tolerance and processability.

Description

Technical Field

[0001] The present invention relates to the technical field of electrode materials, and particularly to a cathode material, a preparation method thereof, and an application thereof. Background Art

[0002] Since 2020, in the face of a several-fold increase in demand, there has been a shortage in the supply of the main raw materials for lithium-ion batteries, lithium carbonate and lithium hydroxide. The price of lithium carbonate soared by more than 10 times at one point, leading to an increase in battery prices, and further resulting in a sharp rise in the production costs of new energy vehicles and energy storage. Taking this opportunity, sodium-ion batteries, as an alternative solution, have come to the fore.

[0003] The transition metal oxide cathode material of sodium-ion batteries has the same "rocking chair" working principle as that of lithium-ion batteries. Moreover, its relatively high discharge voltage, stable structure, and dialysis working mechanism are considered to be a type of cathode material with great industrialization potential. Among them, the O3-phase cathode with a high sodium content has a high sodium storage capacity and is considered to be the most promising transition metal oxide cathode material. However, the poor environmental tolerance of this material greatly hinders the processing performance and electrochemical performance of the material, and it is not suitable for low-cost sodium-ion batteries. Summary of the Invention

[0004] The purpose of the present invention is to provide a cathode material, a preparation method thereof, and an application thereof. The cathode material has both excellent electrochemical performance of the O3-phase cathode and good environmental tolerance and processability.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a cathode material, including an O3 phase and a P3 phase coating layer;

[0007] The chemical composition of the cathode material is: Na a Li b Ni c Fe d Mn e Ti f O 2+β , where a is 0.9 - 1.0, b is 0.01 - 0.03, c is 0.3 - 0.4, d is 0.3 - 0.4, e is 0.3 - 0.4, f is 0.01 - 0.03, and the value of β satisfies the valence balance;

[0008] The valence states of Mn in the cathode material include +2 and +3.

[0009] Preferably, a is 0.9 - 1.0, b is 0.01 - 0.03, c is 0.3 - 0.4, d is 0.3 - 0.4, e is 0.3 - 0.4, f is 0.01 - 0.03, and the value of β satisfies the valence balance.

[0010] Preferably, a is 0.97, b is 0.03, c is 0.33, d is 0.33, e is 0.30, f is 0.03, and the value of β satisfies the valence balance.

[0011] Preferably, the chemical composition of the O3 phase is: Na a1 Li b1 Ni c1 Fe d1 Mn e1 Ti f1 O 2+β1 , where a1 is 0.95 - 1.0, b1 is 0.01 - 0.03, c1 is 0.3 - 0.4, d1 is 0.3 - 0.4, e1 is 0.3 - 0.4, f1 is 0.01 - 0.03, and the value of β1 satisfies the valence balance.

[0012] Preferably, the chemical composition of the P3 phase in the P3 phase coating layer is: Na a2 Li b2 Ni c2 Fe d2 Mn e2 Ti f2 O 2+β2 , where a2 is 0.3 - 0.6, b2 is 0.01 - 0.03, c2 is 0.3 - 0.4, d2 is 0.3 - 0.4, e2 is 0.3 - 0.4, f2 is 0.01 - 0.03, and the value of β2 satisfies the valence balance.

[0013] Preferably, the positive electrode material includes small particles with a particle size of 10 - 200 nm and large particles with a particle size of 1 - 10 μm.

[0014] Preferably, the thickness of the P3 phase coating layer is 1 - 10 nm.

[0015] The present invention also provides a method for preparing the positive electrode material according to the above technical solution, including the following steps:

[0016] After sand - grinding nickel source, iron source, manganese source, soluble lithium salt, soluble sodium salt, titanium source, complexing agent and water, spray granulation is carried out to obtain a composite precursor;

[0017] The composite precursor is pre - sintered to obtain a wet composite metal oxide precursor;

[0018] Sinter the wet composite metal oxide precursor to obtain the positive electrode material.

[0019] Preferably, the complexing agent is one or more of ethylenediaminetetraacetic acid, ethylenediaminetetraacetate, ascorbic acid, and ascorbate;

[0020] The temperature of the pre-sintering is 500-800 °C, the time is 3-5 h, and the heating rate to the temperature of the pre-sintering is 2-5 °C / min;

[0021] The temperature of the sintering is 700-950 °C, the time is 10-15 h, and the heating rate to the temperature of the pre-sintering is 2-5 °C / min.

[0022] The present invention also provides the application of the positive electrode material described in the above technical solution or the positive electrode material prepared by the preparation method described in the above technical solution in a sodium ion battery.

[0023] The present invention provides a positive electrode material, including an O3 phase and a P3 phase coating layer; the chemical composition of the positive electrode material is: Na a Li b Ni c Fe d Mn e Ti f O 2+β , where a is 0.9-1.0, b is 0.01-0.03, c is 0.3-0.4, d is 0.3-0.4, e is 0.3-0.4, f is 0.01-0.03, and the value of β satisfies the valence balance; the valence states of Mn in the positive electrode material include +2 and +3. The positive electrode material described in the present invention is caused by the interlayer ion rearrangement induced by lithium ion doping and the bulk phase structure reorganization induced by titanium element doping, which jointly cause the removal of sodium ions on the surface of the material during high-temperature sintering, resulting in the formation of an O3-phase positive electrode material coated with a P3 phase, and making it have excellent electrochemical performance and environmental tolerance. After 100 cycles under 0.1C charge and discharge conditions, it still has a reversible discharge specific capacity of 150 mA·h·g -1 , and the structure will not change after being placed in humid air for seven months; at the same time, the positive electrode material has excellent cycle performance and discharge capacity, high repeatability, and good uniformity, which has a good driving force for the development of the sodium ion battery industry; compared with the pure O3-phase positive electrode, the positive electrode material induced by the interlayer doping of lithium and the bulk doping of titanium in the present invention greatly improves the material stability while ensuring excellent performance, and has a very broad application prospect in high-stability and high-capacity sodium ion batteries;

[0024] The present invention also provides a method for preparing the cathode material described in the above technical solution, which includes the following steps: mixing a nickel source, an iron source, a manganese source, a soluble lithium salt, a soluble sodium salt, a titanium source, a complexing agent and water, and then performing spray granulation to obtain a composite precursor; pre-sintering the composite precursor and exposing it in a humid environment to obtain a wet composite metal oxide precursor; sintering the wet composite metal oxide precursor to obtain the cathode material. The preparation method of the present invention is simple and easy for large-scale production. Description of the Drawings

[0025] Figure 1 XRD pattern of the cathode material described in Example 1;

[0026] Figure 2 SEM image of the cathode material described in Example 1;

[0027] Figure 3 XRD pattern of the cathode material described in Example 1 after being exposed in humid air (humidity 80%) for 7 months;

[0028] Figure 4 Charge-discharge performance curve of the coin cell prepared with the cathode material described in Example 1 at a 1C rate;

[0029] Figure 5 XRD pattern of the cathode material described in Example 2;

[0030] Figure 6 SEM image of the cathode material described in Example 2;

[0031] Figure 7 XRD pattern of the cathode material described in Example 2 after being exposed in humid air (humidity 80%) for 7 months;

[0032] Figure 8 Charge-discharge performance curve of the coin cell prepared with the cathode material described in Example 2 at a 1C rate;

[0033] Figure 9 Charge-discharge performance curve of the coin cell prepared with the cathode material described in Example 3 at a 1C rate;

[0034] Figure 10 Charge-discharge performance curve of the coin cell prepared with the cathode material described in Example 4 at a 1C rate;

[0035] Figure 11 XRD pattern of the cathode material described in Comparative Example 1;

[0036] Figure 12 XRD pattern of the cathode material described in Comparative Example 1 after being exposed in humid air (humidity 80%) for 7 months;

[0037] Figure 13 The charge-discharge performance curve of the coin cell prepared from the cathode material described in Comparative Example 1 at a rate of 1C;

[0038] Figure 14 The XRD pattern of the cathode material described in Comparative Example 2;

[0039] Figure 15 The charge-discharge performance curve of the coin cell prepared from the cathode material described in Comparative Example 2 at a rate of 1C;

[0040] Figure 16 The XRD pattern of the cathode material described in Comparative Example 3;

[0041] Figure 17 The charge-discharge performance curve of the coin cell prepared from the cathode material described in Comparative Example 3 at a rate of 1C. Detailed Description of the Invention

[0042] The present invention provides a cathode material, including an O3-phase and a P3-phase coating layer;

[0043] The chemical composition of the cathode material is: Na a Li b Ni c Fe d Mn e Ti f O 2+β , where a is 0.9 to 1.0, b is 0.01 to 0.03, c is 0.3 to 0.4, d is 0.3 to 0.4, e is 0.3 to 0.4, f is 0.01 to 0.03, and the value of β satisfies the valence balance;

[0044] The valence states of Mn in the cathode material include +2 and +3.

[0045] In the present invention, the chemical composition of the O3-phase is preferably: Na a1 Li b1 Ni c1 Fe d1 Mn e1 Ti f1 O 2+β1, wherein, a1 is preferably 0.95 to 1.0, b1 is preferably 0.01 to 0.03, c1 is preferably 0.3 to 0.4, d1 is preferably 0.3 to 0.4, e1 is preferably 0.3 to 0.4, f1 is preferably 0.01 to 0.03, and the value of β1 satisfies the valence balance. Among them, a1 is preferably 0.96 to 0.98, b1 is preferably 0.02, c1 is preferably 0.33 to 0.37, d1 is preferably 0.33 to 0.36, e1 is preferably 0.34 to 0.37, f1 is preferably 0.015 to 0.025, and the value of β1 satisfies the valence balance.

[0046] In the present invention, the chemical composition of the P3 phase in the P3 phase coating layer is preferably: Na a2 Li b2 Ni c2 Fe d2 Mn e2 Ti f2 O 2+β2 , wherein, a2 is preferably 0.3 to 0.6, b2 is preferably 0.01 to 0.03, c2 is preferably 0.3 to 0.4, d2 is preferably 0.3 to 0.4, e2 is preferably 0.3 to 0.4, f2 is preferably 0.01 to 0.03, and the value of β2 satisfies the valence balance. Among them, a2 is preferably 0.4 to 0.5, b2 is preferably 0.015 to 0.025, c2 is preferably 0.33 to 0.37, d2 is preferably 0.33 to 0.36, e2 is preferably 0.34 to 0.37, f2 is preferably 0.015 to 0.025, and the value of β2 satisfies the valence balance.

[0047] In the present invention, a is preferably 0.9 to 1.0, b is preferably 0.01 to 0.03, c is preferably 0.3 to 0.4, d is preferably 0.3 to 0.4, e is preferably 0.3 to 0.4, f is preferably 0.01 to 0.03, and the value of β satisfies the valence balance. More preferably, a is 0.97, b is 0.03, c is 0.33, d is 0.33, e is 0.30, f is 0.03, and the value of β satisfies the valence balance.

[0048] In the present invention, the function of the P3 phase coating layer is to improve the stability of the O3 phase cathode material in a humid environment.

[0049] In the present invention, the cathode material preferably includes small particles with a particle size of 10 to 200 nm and large particles with a particle size of 1 to 10 μm.

[0050] In the present invention, the thickness of the P3 phase coating layer is preferably 1 to 10 nm, and more preferably 4 to 6 nm.

[0051] In the present invention, the function of the particle size of the positive electrode material being within the above range is to balance the material processability and the powder compact density, and the function of controlling the thickness of the P3-phase coating layer within the above range is to ensure the discharge capacity of the material on the premise of effective waterproofing.

[0052] The present invention also provides a method for preparing the positive electrode material described in the above technical solution, including the following steps:

[0053] After sand milling a nickel source, an iron source, a manganese source, a soluble lithium salt, a soluble sodium salt, a titanium source, a complexing agent, and water, spray granulation is carried out to obtain a composite precursor;

[0054] The composite precursor is pre-sintered to obtain a wet composite metal oxide precursor;

[0055] The wet composite metal oxide precursor is sintered to obtain the positive electrode material.

[0056] In the present invention, unless otherwise specified, all preparation raw materials are commercially available products well-known to those skilled in the art.

[0057] After sand milling a nickel source, an iron source, a manganese source, a soluble lithium salt, a soluble sodium salt, a titanium source, a complexing agent, and water, spray granulation is carried out to obtain a composite precursor.

[0058] In the present invention, the nickel source preferably includes a soluble nickel salt or nickel oxide; the present invention does not have any special limitation on the type of the soluble nickel salt, and any type well-known to those skilled in the art can be used. In the examples of the present invention, the soluble nickel salt is nickel nitrate hexahydrate.

[0059] In the present invention, the iron source preferably includes a soluble iron salt or iron oxide; the present invention does not have any special limitation on the type of the soluble iron salt, and any type well-known to those skilled in the art can be used. In the examples of the present invention, the soluble iron salt is iron nitrate nonahydrate.

[0060] In the present invention, the manganese source preferably includes a soluble manganese salt or manganese oxide; the present invention does not have any special limitation on the type of the soluble manganese salt, and any type well-known to those skilled in the art can be used. In the examples of the present invention, the soluble manganese salt is manganese chloride.

[0061] In the present invention, the titanium source preferably includes a soluble titanium salt or titanium oxide; the present invention does not have any special limitation on the type of the soluble titanium salt, and any type well-known to those skilled in the art can be used. In the examples of the present invention, the soluble titanium source includes titanium isopropoxide, and the titanium oxide is titanium dioxide.

[0062] The present invention does not have any special limitations on the types of the soluble lithium salt and the soluble sodium salt, and those well-known to those skilled in the art can be used. In the embodiments of the present invention, the soluble lithium salt is lithium acetate or lithium carbonate; the soluble sodium source is sodium nitrate or sodium carbonate.

[0063] In the present invention, the complexing agent is preferably one or more of ethylenediaminetetraacetic acid, ethylenediaminetetraacetate, ascorbic acid, and ascorbate; when there are two or more of the above specific selections for the complexing agent, the present invention does not have any special limitations on the ratio of the above specific substances, and they can be mixed in any ratio.

[0064] In the present invention, the water is preferably deionized water.

[0065] In the present invention, the amounts of the nickel source, iron source, manganese source, soluble lithium salt, soluble sodium salt, and titanium source are preferably mixed according to the elemental composition of the positive electrode material.

[0066] In the mixed solution obtained by mixing in the present invention, the concentration of the nickel source is preferably 1-20 mol / L, more preferably 5-10 mol / L, and most preferably 6-8 mol / L. The concentration of the complexing agent in the mixed solution obtained by mixing is preferably 0.4-8 mol / L, more preferably 1-6 mol / L, and most preferably 2-5 mol / L.

[0067] The present invention does not have any special limitations on the conditions of the sand grinding, and the median particle size of the slurry obtained after sand grinding is less than 1 μm under the conditions well-known to those skilled in the art. In the embodiments of the present invention, the temperature of the sand grinding is 35 °C, the sand grinding medium for sand grinding is zirconia beads with a diameter of 0.5 mm, the linear velocity is 12 m / s, and the time is 10 h.

[0068] The present invention does not have any special limitations on the process of the spray granulation, and the process well-known to those skilled in the art can be used.

[0069] After obtaining the composite precursor, the present invention pre-sinter the composite precursor and expose it in a humid environment to obtain a wet composite metal oxide precursor.

[0070] Before the pre-sintering, the present invention preferably further includes grinding and tableting in sequence. The present invention does not have any special limitations on the processes of the grinding and tableting, and the processes well-known to those skilled in the art can be used. In the embodiments of the present invention, the pressure of the tableting is 20 mbar and the time is 2 min.

[0071] In the present invention, the temperature of the pre-sintering is preferably 500 to 800 °C, more preferably 550 to 750 °C, and most preferably 600 to 700 °C; the time is preferably 3 to 5 h, more preferably 3.5 to 4.5 h, and most preferably 4 h; the heating rate for heating to the temperature of the pre-sintering is preferably 2 to 5 °C / min, more preferably 3 to 4 °C / min.

[0072] In the present invention, the function of the pre-sintering is to prevent the formation of impurity phases caused by gas generation of the precursor.

[0073] After the pre-sintering is completed, the present invention preferably further includes cooling. The present invention has no special limitation on the cooling process, and it can be carried out by using a process well-known to those skilled in the art.

[0074] After the cooling is completed, the present invention preferably further includes exposing the pre-sintered material to a humid environment; the humidity of the humid environment is preferably 0 to 99%, more preferably 20 to 80%, and most preferably 40 to 60%; the temperature is preferably 0 to 100 °C, more preferably 20 to 50 °C, and most preferably 30 to 45 °C; the exposure time is preferably 0 to 1000 min, more preferably 300 to 900 min, and most preferably 500 to 600 min; and neither the humidity nor the exposure time is 0.

[0075] After obtaining the wet composite metal oxide precursor, the present invention sinters the wet composite metal oxide precursor to obtain the positive electrode material.

[0076] In the present invention, the temperature of the sintering is preferably 700 to 950 °C, more preferably 750 to 900 °C, and most preferably 800 to 850 °C; the time is preferably 10 to 15 h, more preferably 12 to 14 h; the heating rate for heating to the temperature of the sintering is preferably 2 to 5 °C / min, more preferably 3 to 5 °C / min.

[0077] In the present invention, the function of the sintering is to achieve the synthesis of the target phase.

[0078] After the sintering is completed, the present invention preferably further includes cooling. The present invention has no special limitation on the cooling process, and it can be carried out by using a process well-known to those skilled in the art.

[0079] The present invention also provides the application of the positive electrode material described in the above technical solution or the positive electrode material prepared by the preparation method described in the above technical solution in a sodium ion battery. The present invention has no special limitation on the application process, and it can be carried out by using a method well-known to those skilled in the art.

[0080] The positive electrode material provided by the present invention, its preparation method and application will be described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0081] Example 1

[0082] Positive electrode material: Na 0.97 Li 0.03 Ni 0.33 Fe 0.33 Mn 0.30 Ti 0.03 O 2+β ; The valence states of Mn include +2 and +3; the positive electrode material has a layered structure, and the layered structure includes an O3-phase layer and a P3-phase coating layer; the O3 phase in the O3-phase layer is Na 1.0 Li 0.03 Ni 0.33 Fe 0.33 Mn 0.30 Ti 0.03 O 2+β1 , and the value of β1 satisfies the valence balance. The P3 phase in the P3-phase coating layer is Na 0.47 Li 0.03 Ni 0.33 Fe 0.33 Mn 0.30 Ti 0.03 O 2+β2 , and the value of β2 satisfies the valence balance; the thickness of the P3-phase coating layer is 1-15 nm; the positive electrode material includes small particles with a particle size of 20-200 nm and large particles with a size of 1-10 μm.

[0083] Preparation method:

[0084] Mix 1 mol of nickel nitrate hexahydrate, 1 mol of iron nitrate nonahydrate, 0.9 mol of manganese chloride, 0.1 mol of titanium isopropoxide, 0.03 mol of lithium acetate, 1 mol of sodium nitrate and acetic acid solution with a concentration of 0.5 mol / L. The mixing is carried out in a sand mill at 35 °C. The sanding medium is zirconia beads with a diameter of 0.5 mm, the linear velocity is 12 m / s, and the time is 10 h. After sanding until the median particle size of the slurry is less than 1 μm, spray granulation is carried out to obtain a metal composite gel precursor;

[0085] The metal composite gel precursor is ground and tableted in sequence (the pressure of tablet pressing is 20 mbar and the time is 2 min) to form a shiny round tablet. In an air atmosphere, it is heated to 550 °C at a heating rate of 4 °C / min and held for 4 h; then it is heated to 910 °C at a heating rate of 3 °C / min and held for 10 h, and then cooled to obtain the positive electrode material;

[0086] Figure 1XRD pattern of the positive electrode material Figure 2 SEM image of the positive electrode material, which shows that Figures 1 - 2 the prepared material is an O3 / P3 mixed-phase single crystal material, and there are relatively fine P3-phase particles on the surface;

[0087] After the positive electrode material was exposed to humid air (humidity 80%) for 7 months, XRD tests were carried out, and the test results are as shown in Figure 3 It can be seen from Figure 3 that the positive electrode material is very stable in water and air, and no phase change occurs after soaking;

[0088] After drying the positive electrode material at 110 °C for 12 h, 8 g of the dried positive electrode material, 1 g of acetylene black, and 1 g of polyvinylidene fluoride were uniformly dispersed in N-methyl-2-pyrrolidone to obtain a slurry; the slurry was coated on aluminum foil, vacuum dried at 110 °C, cut into electrode sheets, and in a glove box filled with high-purity argon, a button cell for testing was assembled with sodium metal as the negative electrode, glass fiber as the separator, and 1 M NaPF6 / EC+DEC (1:1) as the electrolyte.

[0089] The charge-discharge performance of the button cell was tested at a rate of 1 C (voltage range 2.0 - 4.2 V), and the test results are as shown in Figure 4 It can be seen from Figure 4 that the material exhibits typical electrochemical characteristics of O3-phase layered oxides and has a discharge capacity exceeding 160 mAh / g.

[0090] Example 2

[0091] Positive electrode material: Na 0.97 Li 0.03 Ni 0.33 Fe 0.33 Mn 0.30 Ti 0.03 O 2+β ; The valence states of Mn include +2 and +3; the positive electrode material has a layered structure, and the layered structure includes an O3-phase layer and a P3-phase coating layer; the O3 phase in the O3-phase layer is Na 1.0 Li 0.03 Ni 0.33 Fe 0.33 Mn 0.30 Ti 0.03 O 2+β1 , and the value of β1 satisfies the valence balance. The P3 phase in the P3-phase coating layer is Na 0.47 Li 0.03 Ni 0.33 Fe 0.33 Mn 0.30 Ti 0.03 O2+β2 , the value of β2 satisfies the valence balance; the thickness of the P3 phase coating layer is 1 to 10 nm; the positive electrode material includes small particles with a particle size of 20 to 200 nm and large particles with a size of 1 to 10 μm;

[0092] Preparation method:

[0093] Mix 1 mol of nickel oxide, 0.5 mol of iron(III) oxide, 0.9 mol of manganese dioxide, 0.1 mol of titanium dioxide, 0.03 mol of lithium carbonate, 0.6 mol of sodium carbonate and acetic acid solution with a concentration of 0.5 mol / L. The mixing condition is carried out in a sand mill at 35 °C. The sanding medium is zirconia beads with a diameter of 0.5 mm, the linear velocity is 12 m / s, and the time is 10 h. After sanding until the median particle size of the slurry is less than 1 μm, spray granulation is carried out to obtain a metal composite gel precursor;

[0094] Grind and tablet the metal composite gel precursor in sequence (the pressure of tableting is 20 mbar and the time is 2 min) to press into a shiny round sheet. Under an air atmosphere, heat it to 550 °C at a heating rate of 4 °C / min and keep it warm for 4 h; then heat it to 910 °C at a heating rate of 3 °C / min and keep it warm for 10 h, and then cool down to obtain the positive electrode material;

[0095] Figure 5 is the XRD pattern of the positive electrode material, Figure 6 is the SEM image of the positive electrode material. It can be seen from Figures 5 - 6 that the prepared material is an O3 / P3 mixed-phase single crystal material, and there are finer P3 phase particles on the surface;

[0096] After the positive electrode material is exposed to humid air (humidity is 80%) for 7 months, XRD test is carried out. The test results are as shown in Figure 7 It can be seen from Figure 7 that the positive electrode material is very stable in water and air and no phase change occurs after soaking;

[0097] After drying the positive electrode material at 110 °C for 12 h, 8 g of the dried positive electrode material, 1 g of acetylene black and 1 g of polyvinylidene fluoride are uniformly dispersed in N-methyl-2-pyrrolidone to obtain a slurry; the slurry is coated on an aluminum foil, vacuum dried at 110 °C, cut into electrode sheets and in a high-purity argon glove box, using metallic sodium as the negative electrode, using glass fiber as the separator, and using 1 M NaPF6 / EC+DEC (1:1) as the electrolyte to support the test button cell;

[0098] Perform charge and discharge performance test on the button cell at a 1C rate (the voltage range is 2.0 to 4.2 V). The test results are as shown in Figure 8 It can be seen from Figure 8It can be seen that the material exhibits typical electrochemical characteristics of O3-phase layered oxides and has a discharge capacity exceeding 160 mAh / g.

[0099] Example 3

[0100] Cathode material: Na 0.97 Li 0.01 Ni 0.33 Fe 0.33 Mn 0.32 Ti 0.01 O 2+β ; The valence states of Mn include +2 and +3; the cathode material has a layered structure, and the layered structure includes an O3-phase layer and a P3-phase coating layer; the O3-phase in the O3-phase layer is Na 1.0 Li 0.01 Ni 0.33 Fe 0.33 Mn 0.32 Ti 0.01 O 2+β1 , and the value of β1 satisfies the valence balance. The P3-phase in the P3-phase coating layer is Na 0.47 Li 0.01 Ni 0.33 Fe 0.33 Mn 0.32 Ti 0.01 O 2+β2 , and the value of β2 satisfies the valence balance; the thickness of the P3-phase coating layer is 1 - 15 nm; the cathode material includes small particles with a particle size of 20 - 200 nm and large particles with a size of 1 - 10 μm.

[0101] Preparation method:

[0102] Mix 1 mol of nickel nitrate hexahydrate, 1 mol of iron nitrate nonahydrate, 0.9 mol of manganese chloride, 0.03 mol of titanium isopropoxide, 0.01 mol of lithium acetate, 1 mol of sodium nitrate, and acetic acid solution with a concentration of 0.5 mol / L. The mixing is carried out in a sand mill at 35°C. The sanding medium is zirconia beads with a diameter of 0.5 mm, the linear velocity is 12 m / s, and the time is 10 h. After sanding until the median particle size of the slurry is less than 1 micron, spray granulation is carried out to obtain a metal composite gel precursor;

[0103] Grind and tablet the metal composite gel precursor in sequence (the pressure of tableting is 20 mbar and the time is 2 min) to form a shiny round tablet. Under an air atmosphere, heat it to 550°C at a heating rate of 4°C / min and hold for 4 h; then heat it to 910°C at a heating rate of 3°C / min, hold for 10 h, and then cool down to obtain the cathode material;

[0104] After drying the positive electrode material at 110 °C for 12 h, 8 g of the dried positive electrode material, 1 g of acetylene black, and 1 g of polyvinylidene fluoride were uniformly dispersed in N-methyl-2-pyrrolidone to obtain a slurry; the slurry was coated on aluminum foil, vacuum dried at 110 °C, cut into electrode sheets, and in a glove box filled with high-purity argon, a coin cell for testing was assembled with sodium metal as the negative electrode, glass fiber as the separator, and 1 M NaPF6 / EC+DEC (1:1) as the electrolyte.

[0105] The charge-discharge performance of the coin cell was tested at a rate of 1C (voltage range: 2.0 - 4.2 V), and the test results are as Figure 9 shown. It can be seen from Figure 9 that the material exhibited a discharge capacity of 160 mAh / g and a capacity retention rate of 88% after 30 cycles.

[0106] Example 4

[0107] Positive electrode material: Na 0.97 Li 0.01 Ni 0.33 Fe 0.33 Mn 0.32 Ti 0.01 O 2+β ; The valence states of Mn include +2 and +3; the positive electrode material has a layered structure, and the layered structure includes an O3-phase layer and a P3-phase coating layer; the O3-phase in the O3-phase layer is Na 1.0 Li 0.01 Ni 0.33 Fe 0.33 Mn 0.32 Ti 0.01 O 2+β1 , and the value of β1 satisfies the valence balance. The P3-phase in the P3-phase coating layer is Na 0.47 Li 0.01 Ni 0.33 Fe 0.33 Mn 0.32 Ti 0.01 O 2+β2 , and the value of β2 satisfies the valence balance; the thickness of the P3-phase coating layer is 1 - 15 nm; the positive electrode material includes small particles with a particle size of 20 - 200 nm and large particles with a size of 1 - 10 μm.

[0108] Preparation method:

[0109] Mix 1 mol of nickel oxide, 0.5 mol of iron(III) oxide, 0.9 mol of manganese dioxide, 0.03 mol of titanium dioxide, 0.01 mol of lithium carbonate, 0.6 mol of sodium carbonate and acetic acid solution with a concentration of 0.5 mol / L. The mixing conditions are carried out in a sand mill at 35 °C. The sand grinding medium is zirconia beads with a diameter of 0.5 mm, the linear velocity is 12 m / s, and the time is 10 h. After sand grinding until the median particle size of the slurry is less than 1 micron, spray granulation is carried out to obtain a metal composite gel precursor;

[0110] Grind and tablet the metal composite gel precursor in sequence (the pressure for tableting is 20 mbar and the time is 2 min) to press it into a shiny round sheet. Under an air atmosphere, heat it to 550 °C at a heating rate of 4 °C / min and keep it warm for 4 h; then heat it to 910 °C at a heating rate of 3 °C / min and keep it warm for 10 h, and then cool it down to obtain a cathode material;

[0111] After drying the cathode material at 110 °C for 12 h, disperse 8 g of the dried cathode material, 1 g of acetylene black and 1 g of polyvinylidene fluoride evenly in N-methyl-2-pyrrolidone to obtain a slurry; coat the slurry on an aluminum foil, dry it in vacuum at 110 °C, cut it into a pole piece and in a high-purity argon glove box, use metallic sodium as the negative electrode, use glass fiber as the separator, and use 1 M NaPF6 / EC+DEC (1:1) as the electrolyte to support the test of a button cell;

[0112] Perform charge-discharge performance testing on the button cell at a 1C rate (the voltage range is 2.0 - 4.2 V), and the test results are as Figure 10 shown. It can be seen from Figure 10 that the material exhibits a discharge capacity of 162 mAh / g and a capacity retention rate of 90% after 30 cycles.

[0113] Comparative Example 1 (without Ti and Li elements)

[0114] Cathode material: Na 0.97 Ni 0.33 Fe 0.33 Mn 0.33 O 2+β ; The valence states of Mn include +2 and +3; the cathode material has an O3-phase layered structure.

[0115] Preparation method:

[0116] Mix 1 mol of nickel nitrate hexahydrate, 1 mol of iron nitrate nonahydrate, 1 mol of manganese chloride, 1 mol of sodium nitrate and acetic acid solution with a concentration of 0.5 mol / L. The mixing conditions are as follows: perform the mixing in a sand mill at 35 °C. The sanding medium is zirconia beads with a diameter of 0.5 mm, the linear velocity is 12 m / s, and the time is 10 h. After sanding until the median particle size of the slurry is less than 1 micron, perform spray granulation to obtain a metal composite gel precursor;

[0117] Grind and tablet the metal composite gel precursor in sequence (the pressure for tableting is 20 mbar and the time is 2 min) to press it into a shiny round tablet. Under an air atmosphere, heat it to 550 °C at a heating rate of 4 °C / min and keep it warm for 4 h; then heat it to 910 °C at a heating rate of 3 °C / min and keep it warm for 10 h, and then cool it down to obtain a positive electrode material;

[0118] Figure 11 is the XRD pattern of the positive electrode material, from Figure 11 it can be seen that the prepared material is an O3-phase single crystal material;

[0119] After exposing the positive electrode material in humid air (humidity is 80%) for 7 months, perform XRD testing. The test results are as shown in Figure 12 From Figure 12 it can be seen that the positive electrode material is unstable in water and air, and impurity phases are generated after soaking;

[0120] After drying the positive electrode material at 110 °C for 12 h, uniformly disperse 8 g of the dried positive electrode material, 1 g of acetylene black and 1 g of polyvinylidene fluoride in N-methyl-2-pyrrolidone to obtain a slurry; coat the slurry on an aluminum foil, after vacuum drying at 110 °C, cut it into a pole piece and in a high-purity argon glove box, use metallic sodium as the negative electrode, use glass fiber as the separator, and use 1 M NaPF6 / EC+DEC (1:1) as the electrolyte to support the test of a button battery;

[0121] Perform charge and discharge performance testing on the button battery at a 1C rate (the voltage range is 2.0 - 4.2 V). The test results are as shown in Figure 13 From Figure 13 it can be seen that the material capacity is 151 mAh / g and the capacity retention rate after 30 cycles is 70%.

[0122] Comparative Example 2 (without Li element)

[0123] Positive electrode material: Na 0.97 Ni 0.33 Fe 0.33 Mn 0.30 Ti 0.03 O 2+β; The valence states of Mn include +2 and +3; the positive electrode material has an O3-phase layered structure.

[0124] Preparation method:

[0125] Mix 1 mol of nickel nitrate hexahydrate, 1 mol of iron nitrate nonahydrate, 0.9 mol of manganese chloride, 0.1 mol of titanium isopropoxide, 1 mol of sodium nitrate, and an acetic acid solution with a concentration of 0.5 mol / L. The mixing is carried out in a sand mill at 35 °C. The sanding medium is zirconia beads with a diameter of 0.5 mm, the linear velocity is 12 m / s, and the time is 10 h. After sanding until the median particle size of the slurry is less than 1 μm, spray granulation is carried out to obtain a metal composite gel precursor;

[0126] Grind and tablet the metal composite gel precursor in sequence (the pressure for tableting is 20 mbar and the time is 2 min) to form a shiny round tablet. Under an air atmosphere, heat it to 550 °C at a heating rate of 4 °C / min and hold for 4 h; then heat it to 910 °C at a heating rate of 3 °C / min and hold for 10 h, and then cool down to obtain the positive electrode material;

[0127] Figure 14 is the XRD pattern of the positive electrode material. It can be seen from Figure 14 that the prepared material is an O3-phase single crystal material;

[0128] After drying the positive electrode material at 110 °C for 12 h, disperse 8 g of the dried positive electrode material, 1 g of acetylene black, and 1 g of polyvinylidene fluoride evenly in N-methyl-2-pyrrolidone to obtain a slurry; coat the slurry on an aluminum foil, vacuum dry it at 110 °C, cut it into a pole piece, and in a high-purity argon glove box, use metallic sodium as the negative electrode, glass fiber as the separator, and 1 M NaPF6 / EC+DEC (1:1) as the electrolyte to support the test of a button cell;

[0129] Perform charge-discharge performance testing on the button cell at a 1C rate (the voltage range is 2.0 - 4.2 V). The test results are as shown in Figure 15 It can be seen from Figure 15 that the material exhibits a discharge capacity of 150 mAh / g and a capacity retention rate of 68% after 30 cycles.

[0130] Comparative Example 3 (without Ti element)

[0131] Positive electrode material: Na 0.97 Li 0.03 Ni 0.33 Fe 0.33 Mn 0.33 O 2+β ; The valence states of Mn include +2 and +3; the positive electrode material has an O3-phase layered structure.

[0132] Preparation method:

[0133] Mix 1 mol of nickel nitrate hexahydrate, 1 mol of iron nitrate nonahydrate, 1 mol of manganese chloride, 0.03 mol of lithium acetate, 1 mol of sodium nitrate and acetic acid solution with a concentration of 0.5 mol / L. The mixing conditions are carried out in a sand mill at 35 °C. The sand grinding medium is zirconia beads with a diameter of 0.5 mm, the linear velocity is 12 m / s, and the time is 10 h. After sand grinding until the median particle size of the slurry is less than 1 micron, spray granulation is carried out to obtain a metal composite gel precursor;

[0134] Grind and tablet the metal composite gel precursor in sequence (the pressure of tableting is 20 mbar and the time is 2 min) to press into a shiny round tablet. In an air atmosphere, heat it to 550 °C at a heating rate of 4 °C / min and keep it warm for 4 h; then heat it to 910 °C at a heating rate of 3 °C / min and keep it warm for 10 h, and then cool it to obtain the cathode material;

[0135] Figure 16 is the XRD pattern of the cathode material. It can be seen from Figure 16 that the prepared material is an O3-phase single crystal material;

[0136] After drying the cathode material at 110 °C for 12 h, disperse 8 g of the dried cathode material, 1 g of acetylene black and 1 g of polyvinylidene fluoride evenly in N-methyl-2-pyrrolidone to obtain a slurry; coat the slurry on an aluminum foil, after vacuum drying at 110 °C, cut it into a pole piece and in a high-purity argon glove box, use metallic sodium as the anode, use glass fiber as the separator, and use 1M NaPF6 / EC+DEC (1:1) as the electrolyte to support the test coin cell;

[0137] Perform charge-discharge performance tests on the coin cell at a 1C rate (the voltage range is 2.0~4.2V). The test results are as shown in Figure 17 It can be seen from Figure 17 that the discharge capacity of the material is 157 mAh / g and the capacity retention rate after 30 cycles is 65%.

[0138] The above is only the preferred implementation mode of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and retouches can still be made, and these improvements and retouches should also be regarded as the protection scope of the present invention.

Claims

1. A cathode material, characterized in that, It includes an O3 phase and a P3 phase coating layer that coats the O3 phase; The chemical composition of the positive electrode material is: Na a Li b Ni c Fe d Mn e Ti f O 2+β , where a is 0.9 to 1.0, b is 0.01 to 0.03, c is 0.3 to 0.4, d is 0.3 to 0.4, e is 0.3 to 0.4, f is 0.01 to 0.03, and the value of β satisfies the valence balance; The valence states of Mn in the positive electrode material include +2 and +3; The chemical composition of the O3 phase is: Na a1 Li b1 Ni c1 Fe d1 Mn e1 Ti f1 O 2+β1 , where a1 is 0.95 to 1.0, b1 is 0.01 to 0.03, c1 is 0.3 to 0.4, d1 is 0.3 to 0.4, e1 is 0.3 to 0.4, f1 is 0.01 to 0.03, and the value of β1 satisfies the valence balance; The chemical composition of the P3 phase in the P3 phase coating is: Na a2 Li b2 Ni c2 Fe d2 Mn e2 Ti f2 O 2+β2 , where a2 is 0.3 to 0.6, b2 is 0.01 to 0.03, c2 is 0.3 to 0.4, d2 is 0.3 to 0.4, e2 is 0.3 to 0.4, f2 is 0.01 to 0.03, and the value of β2 satisfies the valence balance.

2. The cathode material according to claim 1, characterized in that, Where a is 0.97, b is 0.03, c is 0.33, d is 0.33, e is 0.30, f is 0.03, and the value of β satisfies the valence balance.

3. The cathode material according to claim 1, wherein The positive electrode material includes small particles with a particle size of 10 - 200 nm and large particles with a particle size of 1 - 10 μm.

4. The cathode material according to claim 1 or 3, characterized in that, The thickness of the P3 phase coating layer is 1 - 10 nm.

5. The preparation method of the cathode material according to any one of claims 1 to 4, characterized in that, It includes the following steps: After sand grinding nickel source, iron source, manganese source, soluble lithium salt, soluble sodium salt, titanium source, complexing agent and water, spray granulation is carried out to obtain a composite precursor; The composite precursor is pre-sintered to obtain a wet composite metal oxide precursor; The wet composite metal oxide precursor is sintered to obtain the positive electrode material.

6. The preparation method according to claim 5, characterized in that, The complexing agent is one or several of ethylenediaminetetraacetic acid, ethylenediaminetetraacetate, ascorbic acid and ascorbate; The temperature of the pre-sintering is 500 - 800 °C, the time is 3 - 5 h, and the heating rate to the temperature of the pre-sintering is 2 - 5 °C / min; The temperature of the sintering is 700 - 950 °C, the time is 10 - 15 h, and the heating rate to the temperature of the pre-sintering is 2 - 5 °C / min.

7. Application of the positive electrode material according to any one of claims 1 - 4 or the positive electrode material prepared by the preparation method according to claim 5 or 6 in a sodium ion battery.

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