Cathode material, preparation method and application thereof

Abstract

The application relates to the field of batteries, and discloses a positive electrode material and a preparation method and application thereof. x N y MO2, wherein 0.5<=x<=1.04, 0<y<=0.06; the N element is selected from at least one of Li, K, Mg, Ca, Sr, La, Y, Ba and Zn; the M element is selected from at least two of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Sr, Zr, Nb, Mo, Ta, W, Ce and Eu; the surface residual sodium content of the positive electrode material is not more than 5000 ppm in terms of Na + ; and the particle size distribution span of the positive electrode material satisfies 1-1.5. The positive electrode material has high uniformity, narrow particle size distribution and low surface residual sodium, and can improve the specific capacity and cycle performance of a battery when used in the battery.

Description

Technical Field

[0001] This invention relates to the field of batteries, specifically to a cathode material, its preparation method, and its application. Background Technology

[0002] In recent years, the rapid development of electric vehicles, portable electric devices, and energy storage stations has driven a huge demand for lithium-ion batteries. However, the limited availability and uneven distribution of lithium resources have raised concerns about raw material shortages and rapidly increasing costs. To address this issue, various energy storage devices have been developed over the past few decades. Among them, sodium-ion batteries are considered a promising complementary technology to lithium-ion batteries. Sodium-ion batteries possess advantages such as abundant sodium resources, a similar working principle, and wide temperature range performance, making them significant for future development.

[0003] Theoretically, sodium-ion batteries can reduce material costs by 30%-40% compared to lithium-ion batteries. The main cost reduction methods are replacing lithium in the positive electrode and electrolyte, using anthracite as a raw material to reduce the cost of the negative electrode, and replacing copper foil with aluminum foil for the negative electrode current collector. However, in reality, the industry generally believes that sodium-ion batteries are still in the early stages of industrialization. Production technology is not mature enough and economies of scale have not yet been achieved. Although theoretically cheaper, the cost advantage is not currently apparent. Furthermore, the current co-precipitation high-temperature solid-state sintering method for synthesizing transition metal layered sodium-ion battery positive electrode materials results in excessive residual sodium on the surface and severe material agglomeration, affecting the material's processing performance and electrochemical performance. The main reason is Na... + With a large radius, during the high-temperature solid-state reaction between the precursor and sodium salt, Na... + The slow penetration into the material's interior leads to excessively high levels of residual sodium in certain areas. Summary of the Invention

[0004] To overcome the problems of particle agglomeration, excessively wide particle size distribution, and excessively high residual sodium on the surface of sodium-ion battery cathode materials in existing technologies, this paper provides a cathode material, its preparation method, and its application. This cathode material has high uniformity, narrow particle size distribution, and low residual sodium on the surface.

[0005] To achieve the above objectives, a first aspect of the present invention provides a cathode material, wherein the cathode material has the general chemical formula Na. x N y MO2, where 0.5 ≤ x ≤ 1.04, 0 <y≤0.06;

[0006] The nitrogen element is selected from at least one of Li, K, Mg, Ca, Sr, La, Y, Ba, and Zn;

[0007] The element M is selected from at least two of the following: Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Sr, Zr, Nb, Mo, Ta, W, Ce, and Eu.

[0008] Take Na + The residual sodium content on the surface of the cathode material is calculated to be no more than 5000 ppm;

[0009] The particle size distribution of the positive electrode material has a diameter of 1-1.5.

[0010] A second aspect of the present invention provides a method for preparing a cathode material, the method comprising the following steps:

[0011] (1) In the presence of a solvent, a mixed salt solution is obtained by mixing Na salt, a soluble salt of N element and a soluble salt of M element, and then atomized and subjected to a first heat treatment to obtain powder.

[0012] (2) The powder is placed in a fluidized bed for a second heat treatment, then separated, collected, and cooled to obtain the positive electrode material;

[0013] Wherein, 100℃≤T2-T1≤400℃, T1 is the temperature of the first heat treatment, and T2 is the temperature of the second heat treatment.

[0014] A third aspect of the present invention provides a cathode material prepared by the method described in the second aspect of the present invention.

[0015] The fourth aspect of the present invention provides an application of the cathode material provided in the first and third aspects of the present invention in a sodium-ion battery.

[0016] The beneficial technical effects of this invention are as follows:

[0017] (1) The positive electrode material provided by the present invention has high uniformity, narrow particle size distribution and low residual sodium on the surface. Its use in batteries can improve the specific capacity and cycle performance of batteries.

[0018] (2) The preparation method provided by the present invention has a short process and low cost, and does not use ammonia or alkaline solution, and does not generate sulfate-containing wastewater; preferably, the exhaust gas of the second heat treatment can also be used to preheat the atmosphere of the first heat treatment. Attached Figure Description

[0019] Figure 1 This is a scanning electron microscope image of the cathode material prepared in Example 1;

[0020] Figure 2 Here is a scanning electron microscope image of the cathode material prepared in Comparative Example 1;

[0021] Figure 3 The graph shows the capacity retention rate of button cells prepared using the cathode materials of Example 1 and Comparative Example 1 after 50 cycles. Detailed Implementation

[0022] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0023] The first aspect of this invention provides a cathode material, the general chemical formula of which is Na. x N y MO2, where 0.5 ≤ x ≤ 1.04, 0 <y≤0.06;

[0024] The nitrogen element is selected from at least one of Li, K, Mg, Ca, Sr, La, Y, Ba, and Zn;

[0025] The element M is selected from at least two of the following: Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Sr, Zr, Nb, Mo, Ta, W, Ce, and Eu.

[0026] Take Na + The residual sodium content on the surface of the cathode material is calculated to be no more than 5000 ppm;

[0027] The particle size distribution of the cathode material has a diameter of 1-1.5.

[0028] In this invention, the method for calculating the radial distance is (D 90 -D 10 ) / D 50 D 10 D 50 and D 90 These are the particle size values ​​corresponding to cumulative volume percentages of 10%, 50%, and 90%, respectively.

[0029] The cathode material provided by this invention has high uniformity, narrow particle size distribution, and low residual sodium on the surface. Its use in batteries can improve the specific capacity and cycle performance of the batteries.

[0030] In this invention, the residual sodium content on the surface is a mass content.

[0031] According to a preferred embodiment of the present invention, the positive electrode material has the general chemical formula Na. x N y MO2 satisfies: 0.7≤x≤1.02, 0.02≤y≤0.05.

[0032] In this invention, when the chemical formula of the cathode material satisfies the above-mentioned general formula, the specific capacity and cycle performance of the battery can be further improved.

[0033] According to the present invention, preferably, the N element is selected from at least one of Li, Mg, Ca, La and Zn.

[0034] In this invention, when the N element is selected from the above range, the capacity of the resulting battery can be further improved.

[0035] According to the present invention, preferably, the element M satisfies 1.2 ≤ EN M ≤2.0, where EN M This represents the electronegativity of element M.

[0036] In this invention, when the M element is selected from the above range, it can further stabilize the R-3m layered structure slippage of the material during cycling and improve the cycle stability of the battery.

[0037] In this invention, the electronegativity of the elements is based on the Pauling electronegativity table.

[0038] According to a preferred embodiment of the present invention, Na + The residual sodium content on the surface of the cathode material is calculated to be no more than 3000 ppm.

[0039] According to a particularly preferred embodiment of the present invention, the positive electrode material has the general chemical formula Na. x N y MO2 satisfies 0.7≤x≤1.02, 0.02≤y≤0.05, N is Zn, M is Ni, Fe and Mn, and the atomic ratio of Ni, Fe and Mn is 1:0.8-1.2:0.8-1.2.

[0040] In this invention, when the residual sodium content on the surface of the positive electrode material is within the above-mentioned range, it can reduce high-temperature gas generation in batteries using the positive electrode material, improve battery stability, and extend battery life.

[0041] According to the present invention, preferably, the particle size distribution of the positive electrode material has a diameter of 1.1-1.3.

[0042] In this invention, when the diameter of the positive electrode material is within the above-mentioned range, the rate performance and cycle stability of the battery using the positive electrode material can be further improved.

[0043] According to the present invention, preferably, the D of the positive electrode material 50 It is 3-15μm.

[0044] In this invention, the D of the positive electrode material 50Within the above range, the requirements for battery capacity and cycle stability can be met simultaneously.

[0045] More preferably, the D of the positive electrode material 50 It is 4-6 μm.

[0046] A second aspect of the present invention provides a method for preparing a cathode material, the method comprising the following steps:

[0047] (1) In the presence of a solvent, a mixed salt solution is obtained by mixing Na salt, a soluble salt of N element and a soluble salt of M element, and then atomized and subjected to a first heat treatment to obtain powder.

[0048] (2) The powder is placed in a fluidized bed for a second heat treatment, then separated, collected, and cooled to obtain the positive electrode material;

[0049] Wherein, 100℃≤T2-T1≤400℃, T1 is the temperature of the first heat treatment, and T2 is the temperature of the second heat treatment.

[0050] The preparation method provided by this invention has a short process and low cost. It does not use ammonia or alkaline solution, does not require acid-base neutralization, and does not produce sulfate-containing wastewater. Heat treatment in a fluidized bed can effectively suppress segregation, resulting in a cathode material with high uniformity, narrow particle size distribution, and low residual sodium on the surface. Its use in batteries can improve the specific capacity and cycle performance of the batteries.

[0051] In this invention, the Na salt can be at least one of the following: Na chloride, sulfate, nitrate, carbonate, and bicarbonate.

[0052] Soluble salts of nitrogen (N) and manganese (M) can be soluble chlorides, sulfates, and nitrates. For example, soluble salts of nitrogen (Ni) can be nickel nitrate, nickel sulfate, nickel chloride, and nickel bicarbonate; soluble salts of iron (Fe) can be ferrous sulfate, ferrous chloride, ferrous nitrate, ferric sulfate, ferric chloride, and ferric nitrate; soluble salts of manganese (Mn) can be manganese sulfate, manganese chloride, manganese nitrate, and sodium permanganate; and soluble salts of zinc (Zn) can be zinc sulfate, zinc chloride, and zinc nitrate.

[0053] According to a preferred embodiment of the present invention, in step (1), the total metal ion concentration in the mixed salt solution is 0.2-5 mol / L.

[0054] In this invention, when the total metal ion concentration is within the above-mentioned range, the nucleation rate is more moderate, and the resulting cathode material has a more suitable particle size.

[0055] More preferably, the total metal ion concentration in the mixed salt solution is 0.5-3 mol / L.

[0056] According to the present invention, preferably, the atomization pressure is 0.01-1 MPa.

[0057] According to a specific embodiment of the present invention, the mixed salt solution is preheated before atomization, and the preheating temperature (T) is... 溶液 ) and the boiling point temperature of the solution (T) 沸点 ) satisfies 0≤T 沸点 -T 溶液 ≤10℃.

[0058] In this invention, when the atomization pressure is within the above-mentioned range, droplets of more suitable size and more uniformity can be obtained.

[0059] More preferably, the atomization pressure is 0.05-0.5 MPa.

[0060] According to the present invention, preferably, an oxidizing gas is used as the first carrier gas to spray the atomized mixed salt solution, wherein the flow rate of the first carrier gas is 0.1-1 m / s and the pressure is 0.05-1 MPa.

[0061] In this invention, when the flow rate of the first carrier gas is within the above-mentioned range, a precursor with suitable particle size, uniform distribution, and excellent crystallinity can be further prepared; when the pressure of the first carrier gas is within the above-mentioned range, it is more conducive to the rapid evaporation of the solvent and the pyrolysis of the solute.

[0062] More preferably, the flow rate of the first carrier gas is 0.2-0.6 m / s and the pressure is 0.1-0.5 MPa.

[0063] According to the present invention, preferably, in step (1), T1 is 600-800℃.

[0064] Preferably, the duration of the first heat treatment is 3-30 seconds;

[0065] In this invention, when the temperature and time of the first heat treatment are within the above-mentioned range, the uniformity of the cathode material can be further improved.

[0066] More preferably, in step (1), T1 is 650-750℃.

[0067] More preferably, the duration of the first heat treatment is 10-20 seconds;

[0068] In this invention, the conditions of the second heat treatment have a significant impact on the performance of the cathode material.

[0069] According to the present invention, preferably, in step (2), T2 is 700-1100℃.

[0070] Preferably, the second heat treatment time is 5-15 hours.

[0071] In this invention, when the temperature and time of the second heat treatment are within the above-mentioned range, the distribution of each element in the cathode material can be made more uniform, thereby further improving the specific capacity and cycle retention rate of the battery using the cathode material.

[0072] More preferably, in step (2), T2 is 850-1000℃.

[0073] More preferably, the second heat treatment time is 6-12 hours.

[0074] According to the present invention, preferably, the first heat treatment is carried out in an oxidizing atmosphere, which is preferably air and / or oxygen.

[0075] According to a preferred embodiment of the present invention, in step (2), the powder is fluidized using a second carrier gas, which is an oxygen-containing atmosphere, such as compressed air or oxygen.

[0076] In this invention, fluidization refers to the process by which powder, under the action of a carrier gas, overcomes the weight of the powder and the friction between powder particles, changing from a static stacked state to a suspended and flowing state.

[0077] More preferably, the second carrier gas is compressed air, wherein the dew point of the compressed air is ≤-40°C and the CO2 content is ≤50ppm(v%).

[0078] According to the present invention, preferably, the flow rate of the second carrier gas is 0.5-10 m / s.

[0079] In this invention, when the flow rate of the second carrier gas is within the above-mentioned range, the fluidization of the powder can be made more uniform.

[0080] More preferably, the flow rate of the second carrier gas is 1-7 m / s.

[0081] According to the present invention, preferably, the fluidized bed has a bed filling rate of 20%-70% in the fluidized state.

[0082] In this invention, when the bed filling rate is within the above-mentioned range, the powder suspension is better and the gas-solid contact efficiency is better.

[0083] More preferably, the fluidized bed has a bed filling rate of 40%-60% in the fluidized state.

[0084] According to the present invention, preferably, the bed pressure drop in the fluidized state of the fluidized bed is 0.01-0.05 MPa.

[0085] In this invention, when the bed pressure drop in the fluidized bed state is within the above-mentioned range, the fluidization is more stable.

[0086] More preferably, the bed pressure drop in the fluidized state of the fluidized bed is 0.02-0.04 MPa.

[0087] According to one specific embodiment of the present invention, the product after the second heat treatment is separated and collected by a cyclone separator.

[0088] A third aspect of the present invention provides a cathode material prepared by the method described in the second aspect of the present invention.

[0089] The fourth aspect of the present invention provides an application of the cathode material provided in the first and third aspects of the present invention in a sodium-ion battery.

[0090] The present invention will be described in detail below through embodiments.

[0091] In the following embodiments, the particle size of the cathode material was determined according to the method of GB / T 19077-2016 and obtained using a Mastersizer 3000 laser particle size analyzer.

[0092] Method for determining residual sodium on the surface: Take 10g of the test material and add it to 100mL of anhydrous ethanol. Stir thoroughly and let stand for 5min. Separate the filtrate by vacuum filtration. Obtain the NaOH content of the target material in ethanol by potentiometric titration. Take 5g of the test material and add it to 100mL of ultrapure water. Stir thoroughly and let stand for 5min. Separate the filtrate by vacuum filtration. Obtain the Na2CO3 content of the test material in ultrapure water by potentiometric titration.

[0093] Particle size distribution was determined using a laser particle size analyzer, with the diameter measured via (D). 90 -D 10 ) / D 50 Calculate, where D 10 D 50 and D 90 These are the particle size values ​​corresponding to cumulative volume percentages of 10%, 50%, and 90%, respectively.

[0094] Unless otherwise specified, all reagents and raw materials are commercially available.

[0095] Example 1

[0096] Sodium chloride, nickel chloride hexahydrate, ferric chloride, manganese chloride tetrahydrate, and zinc chloride were added to deionized water in a metal atomic molar ratio of Na:Ni:Fe:Mn:Zn = 1:0.33:0.33:0.34:0.04. The mixture was mechanically stirred at 600 r / min for 30 min to obtain a homogeneous metal salt solution with a total metal ion concentration of 2 mol / L.

[0097] The mixed salt solution was preheated to 90°C and atomized at 0.05 MPa. Then, oxygen at 0.5 MPa was used as the first carrier gas to send the atomized droplets into a calcining furnace for the first heat treatment. The carrier gas flow rate was 0.35 m / s, the temperature of the first heat treatment was 700°C, and the time was 10 s.

[0098] The obtained cathode material precursor was fed into a fluidized bed via a pipeline under gravity for a second heat treatment at a temperature of 900℃, with a temperature difference of 200℃ between the second and first heat treatments. Compressed air (dew point -40℃, CO2 content 50ppm) was introduced as the second carrier gas at a flow rate of 2 m / s, a bed filling rate of 60%, and a bed pressure drop of 0.02 MPa. The cathode material precursor underwent the second heat treatment in the fluidized bed for 8 hours, after which the product was separated and collected by a cyclone separator.

[0099] Example 2

[0100] Sodium chloride, nickel chloride hexahydrate, ferric chloride, manganese chloride tetrahydrate, and zinc chloride were added to deionized water in a metal atomic molar ratio of Na:Ni:Fe:Mn:Zn = 1:0.33:0.33:0.34:0.04. The mixture was mechanically stirred at 600 r / min for 30 min to obtain a homogeneous metal salt solution with a total metal ion concentration of 2 mol / L.

[0101] The mixed salt solution was preheated to 90°C and atomized at 0.05 MPa. Then, oxygen at 0.5 MPa was used as the first carrier gas to send the atomized droplets into a calcining furnace for the first heat treatment. The carrier gas flow rate was 0.35 m / s, the temperature of the first heat treatment was 750°C, and the time was 10 s.

[0102] The obtained cathode material precursor was fed into a fluidized bed via a pipeline under gravity for a second heat treatment at a temperature of 950℃, with a temperature difference of 200℃ between the second and first heat treatments. Compressed air (dew point -40℃, CO2 content 50ppm) was introduced as the second carrier gas at a flow rate of 1.8 m / s, a bed filling rate of 60%, and a bed pressure drop of 0.02 MPa. The cathode material precursor underwent the second heat treatment in the fluidized bed for 9 hours, after which the product was separated and collected by a cyclone separator.

[0103] Example 3

[0104] Sodium chloride, nickel chloride hexahydrate, ferric chloride, manganese chloride tetrahydrate, and zinc chloride were added to deionized water in a metal atomic molar ratio of Na:Ni:Fe:Mn:Zn = 1:0.33:0.33:0.34:0.04. The mixture was mechanically stirred at 600 r / min for 30 min to obtain a homogeneous metal salt solution with a total metal ion concentration of 2 mol / L.

[0105] The mixed salt solution was preheated to 90°C and atomized at 0.05 MPa. Then, oxygen at 0.5 MPa was used as the first carrier gas to send the atomized droplets into a calcining furnace for the first heat treatment. The carrier gas flow rate was 0.35 m / s, the temperature of the first heat treatment was 650°C, and the time was 10 s.

[0106] The obtained cathode material precursor was fed into a fluidized bed via a pipeline under gravity for a second heat treatment at a temperature of 850℃, with a temperature difference of 200℃ between the second and first heat treatments. Compressed air (dew point -40℃, CO2 content 50ppm) was introduced as the second carrier gas at a flow rate of 2.2 m / s, a bed filling rate of 60%, and a bed pressure drop of 0.02 MPa. The cathode material precursor underwent the second heat treatment in the fluidized bed for 7 hours, after which the product was separated and collected by a cyclone separator.

[0107] Example 4

[0108] Sodium chloride, nickel chloride hexahydrate, ferric chloride, manganese chloride tetrahydrate, and zinc chloride were added to deionized water in a metal atomic molar ratio of Na:Ni:Fe:Mn:Zn = 1:0.33:0.33:0.34:0.04. The mixture was mechanically stirred at 600 r / min for 30 min to obtain a homogeneous metal salt solution with a total metal ion concentration of 2 mol / L.

[0109] The mixed salt solution was preheated to 90°C and atomized at 0.05 MPa. Then, oxygen at 0.5 MPa was used as the first carrier gas to send the atomized droplets into a calcining furnace for the first heat treatment. The carrier gas flow rate was 0.35 m / s, the temperature of the first heat treatment was 800°C, and the time was 10 s.

[0110] The obtained cathode material precursor was fed into a fluidized bed via a pipeline under gravity for a second heat treatment at a temperature of 1000℃, with a temperature difference of 200℃ between the second and first heat treatments. Compressed air (dew point -40℃, CO2 content 50ppm) was introduced as the second carrier gas at a flow rate of 1.6 m / s, a bed filling rate of 60%, and a bed pressure drop of 0.02 MPa. The cathode material precursor underwent the second heat treatment in the fluidized bed for 10 hours, after which the product was separated and collected by a cyclone separator.

[0111] Example 5

[0112] Sodium chloride, nickel chloride hexahydrate, ferric chloride, manganese chloride tetrahydrate, and zinc chloride were added to deionized water in a metal atomic molar ratio of Na:Ni:Fe:Mn:Zn = 1:0.33:0.33:0.34:0.04. The mixture was mechanically stirred at 600 r / min for 30 min to obtain a homogeneous metal salt solution with a total metal ion concentration of 2 mol / L.

[0113] The mixed salt solution was preheated to 90°C and atomized at 0.05 MPa. Then, oxygen at 0.5 MPa was used as the first carrier gas to send the atomized droplets into a calcining furnace for the first heat treatment. The carrier gas flow rate was 0.35 m / s, the temperature of the first heat treatment was 600°C, and the time was 10 s.

[0114] The obtained cathode material precursor was fed into a fluidized bed via a pipeline under gravity for a second heat treatment at a temperature of 800℃, with a temperature difference of 200℃ between the second and first heat treatments. Compressed air (dew point -40℃, CO2 content 50ppm) was introduced as the second carrier gas at a flow rate of 2.4 m / s, a bed filling rate of 60%, and a bed pressure drop of 0.02 MPa. The cathode material precursor underwent the second heat treatment in the fluidized bed for 6 hours, after which the product was separated and collected by a cyclone separator.

[0115] Example 6

[0116] Sodium chloride, nickel chloride hexahydrate, ferric chloride, manganese chloride tetrahydrate, and zinc chloride were added to deionized water in a metal atomic molar ratio of Na:Ni:Fe:Mn:Zn = 1:0.26:0.35:0.39:0.04. The mixture was mechanically stirred at 600 r / min for 30 min to obtain a homogeneous metal salt solution with a total metal ion concentration of 2 mol / L.

[0117] The mixed salt solution was preheated to 90°C and atomized at 0.05 MPa. Then, oxygen at 0.5 MPa was used as the first carrier gas to send the atomized droplets into a calcining furnace for the first heat treatment. The carrier gas flow rate was 0.35 m / s, the temperature of the first heat treatment was 700°C, and the time was 10 s.

[0118] The obtained cathode material precursor was fed into a fluidized bed via a pipeline under gravity for a second heat treatment at a temperature of 1000℃, with a temperature difference of 300℃ between the second and first heat treatments. Compressed air (dew point -40℃, CO2 content 50ppm) was introduced as the second carrier gas at a flow rate of 2.0 m / s, a bed filling rate of 60%, and a bed pressure drop of 0.02 MPa. The cathode material precursor underwent the second heat treatment in the fluidized bed for 8 hours, after which the product was separated and collected by a cyclone separator.

[0119] Example 7

[0120] Sodium chloride, nickel chloride hexahydrate, ferric chloride, manganese chloride tetrahydrate, and calcium chloride were added to deionized water in a metal atomic molar ratio of Na:Ni:Fe:Mn:Ca = 1:0.33:0.33:0.34:0.04. The mixture was mechanically stirred at 600 r / min for 30 min to obtain a homogeneous metal salt solution with a total metal ion concentration of 2 mol / L.

[0121] The mixed salt solution was preheated to 90°C and atomized at 0.05 MPa. Then, oxygen at 0.5 MPa was used as the first carrier gas to send the atomized droplets into a calcining furnace for the first heat treatment. The carrier gas flow rate was 0.35 m / s, the temperature of the first heat treatment was 700°C, and the time was 10 s.

[0122] The obtained cathode material precursor was fed into a fluidized bed via a pipeline under gravity for a second heat treatment at a temperature of 1000℃, with a temperature difference of 300℃ between the second and first heat treatments. Compressed air (dew point -40℃, CO2 content 50ppm) was introduced as the second carrier gas at a flow rate of 2.0 m / s, a bed filling rate of 60%, and a bed pressure drop of 0.02 MPa. The cathode material precursor underwent the second heat treatment in the fluidized bed for 8 hours, after which the product was separated and collected by a cyclone separator.

[0123] Example 8

[0124] Sodium chloride, nickel chloride hexahydrate, ferric chloride, manganese chloride tetrahydrate, and lanthanum chloride were added to deionized water in a metal atomic molar ratio of Na:Ni:Fe:Mn:La = 1:0.33:0.33:0.34:0.04. The mixture was mechanically stirred at 600 r / min for 30 min to obtain a homogeneous metal salt solution with a total metal ion concentration of 2 mol / L.

[0125] The mixed salt solution was preheated to 90°C and atomized at 0.05 MPa. Then, oxygen at 0.5 MPa was used as the first carrier gas to send the atomized droplets into a calcining furnace for the first heat treatment. The carrier gas flow rate was 0.35 m / s, the temperature of the first heat treatment was 700°C, and the time was 10 s.

[0126] The obtained cathode material precursor was fed into a fluidized bed via a pipeline under gravity for a second heat treatment at a temperature of 1000℃, with a temperature difference of 300℃ between the second and first heat treatments. Compressed air (dew point -40℃, CO2 content 50ppm) was introduced as the second carrier gas at a flow rate of 2.0 m / s, a bed filling rate of 60%, and a bed pressure drop of 0.02 MPa. The cathode material precursor underwent the second heat treatment in the fluidized bed for 8 hours, after which the product was separated and collected by a cyclone separator.

[0127] Comparative Example 1

[0128] Nickel chloride hexahydrate, ferric chloride, and manganese chloride tetrahydrate were added to deionized water at a metal atomic molar ratio of Ni:Fe:Mn = 0.33:0.33:0.34. The mixture was mechanically stirred at 600 rpm for 30 min to obtain a homogeneous metal salt solution with a metal concentration of 2 mol / L. The mixed salt solution was atomized and pyrolyzed in a calcining furnace using oxygen as the carrier gas at a flow rate of 5 L / min and a pyrolysis temperature of 700 °C. The product deposited in the calcining furnace (the precursor for the cathode material) was weighed, and 10 kg of the precursor, 6.74 kg of sodium carbonate, and 424 g of zinc oxide were added to a mixer and mixed at 800 rpm for 30 min. The mixed material was then calcined in air. The temperature was increased to 1000 °C at a rate of 4 °C / min and held for 8 h. The mixture was then naturally cooled to below 100 °C to obtain the cathode material.

[0129] Comparative Example 2

[0130] Weigh the Ni obtained by the coprecipitation method 1 / 3 Fe 1 / 3 Mn 1 / 3 10 kg of (OH)₂ precursor, 5.886 kg of sodium carbonate, and 361.61 g of zinc oxide were added to a mixer and mixed for 30 min at 800 r / min. Calcination was then carried out in air. The temperature was increased to 1000℃ at a rate of 4℃ / min and held for 10 h. The mixture was then naturally cooled to below 100℃ to obtain the cathode material.

[0131] Comparative Example 3

[0132] Sodium chloride, manganese chloride tetrahydrate, and zinc chloride were added to deionized water in a metal atomic molar ratio of Na:Mn:Zn = 1:1:0.04. The mixture was mechanically stirred at 600 r / min for 30 min to obtain a homogeneous metal salt solution with a total metal ion concentration of 2 mol / L.

[0133] The mixed salt solution was preheated to 90°C and atomized at 0.05 MPa. Then, oxygen at 0.5 MPa was used as the first carrier gas to send the atomized droplets into a calcining furnace for the first heat treatment. The carrier gas flow rate was 0.35 m / s, the temperature of the first heat treatment was 700°C, and the time was 10 s.

[0134] The obtained cathode material precursor was fed into a fluidized bed via a pipeline under gravity for a second heat treatment at a temperature of 1000℃, with a temperature difference of 300℃ between the second and first heat treatments. Compressed air (dew point -40℃, CO2 content 50ppm) was introduced as the second carrier gas at a flow rate of 2.0 m / s, a bed filling rate of 60%, and a bed pressure drop of 0.02 MPa. The cathode material precursor underwent the second heat treatment in the fluidized bed for 8 hours, after which the product was separated and collected by a cyclone separator.

[0135] Test Example 1

[0136] The chemical composition of the cathode materials obtained in the above examples and comparative examples was obtained by measuring the amount of feed, and the particle size distribution and residual sodium on the surface of the cathode materials obtained in the above examples and comparative examples were measured. The results are shown in Table 1.

[0137] Table 1

[0138]

[0139]

[0140] Figure 1 , Figure 2 These are scanning electron microscope (SEM) images of the cathode materials prepared in Example 1 and Comparative Example 1, respectively. It can be seen that... Figure 1 The particles are more uniform in size.

[0141] Test Example 2

[0142] The positive electrode materials obtained in the above examples and comparative examples were used to prepare coin cells. Specifically, the positive electrode material, acetylene black, and polyvinylidene fluoride (PVDF) were mixed and stirred evenly in a mass ratio of 90:5:5. N-methylpyrrolidone (NMP) was added and a degassing mechanism was used to obtain a mixed slurry. The slurry was uniformly coated on the surface of aluminum foil. It was vacuum dried at 80°C for 12 hours and then cut into small round pieces with a diameter of 12 mm using a slicing machine as positive electrode pieces. CR2032 type coin cells were assembled in a glove box filled with Ar gas, wherein the counter electrode was a sodium metal sheet, the separator was glass fiber, and the electrolyte was 1.2 mol / L NaPF6 (sodium hexafluorophosphate), wherein the solvent was EC (ethylene carbonate): PC (propylene carbonate): EMC (methyl ethyl carbonate) = 1:1:1 (volume ratio).

[0143] The constant current-constant voltage method was used to test the battery's initial discharge specific capacity at 25℃, with a voltage range of 2.0-4.0V and a charge / discharge rate of 0.1C. The capacity retention rate was tested after 50 cycles at a charge / discharge rate of 1C, with a cutoff current of 0.05C for all cycles. The results are shown in Table 2.

[0144] Table 2

[0145]

[0146]

[0147] Figure 3 The graph shows the capacity retention rate of button cells prepared with the cathode materials of Example 1 and Comparative Example 1 after 50 cycles. It can be seen that the capacity retention rate of the cathode material of Example 1 is significantly higher than that of Comparative Example 1.

[0148] As can be seen from the results in Tables 1 and 2, the cathode material provided by this invention has high uniformity, narrow particle size distribution, and low residual sodium on the surface. Its use in batteries can improve the specific capacity and cycle performance of the batteries.

[0149] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A positive electrode material, characterized in that, The general chemical formula of the cathode material is Na. x N y MO2, where 0.5 ≤ x ≤ 1.04, 0 <y≤0.06; The nitrogen element is selected from at least one of Li, K, Mg, Ca, Sr, La, Y, Ba, and Zn; The element M is selected from at least two of the following: Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Sr, Zr, Nb, Mo, Ta, W, Ce, and Eu. Take Na + The residual sodium content on the surface of the cathode material is calculated to be no more than 5000 ppm; The particle size distribution of the cathode material has a diameter of 1-1.

5.

2. The cathode material according to claim 1, characterized in that, 0.7≤x≤1.02, 0.02≤y≤0.05; Preferably, the nitrogen element is selected from at least one of Li, Mg, Ca, La and Zn; Preferably, element M satisfies 1.2 ≤ EN M ≤2, where EN M This represents the electronegativity of element M.

3. The cathode material according to claim 1 or 2, characterized in that, Take Na + The residual sodium content on the surface of the cathode material is calculated to be no more than 3000 ppm; Preferably, the particle size distribution of the positive electrode material has a diameter spacing of 1.1-1.

3. Preferably, the D of the positive electrode material 50 It is 3-10μm.

4. A method for preparing a positive electrode material, characterized in that, The method includes the following steps: (1) In the presence of a solvent, a mixed salt solution is obtained by mixing Na salt, a soluble salt of N element and a soluble salt of M element, and then atomized and subjected to a first heat treatment to obtain powder. (2) The powder is placed in a fluidized bed for a second heat treatment, then separated, collected, and cooled to obtain the positive electrode material; Wherein, 100℃≤T2-T1≤400℃, T1 is the temperature of the first heat treatment, and T2 is the temperature of the second heat treatment.

5. The method according to claim 4, characterized in that, In step (1), the total metal ion concentration in the mixed salt solution is 0.2-5 mol / L; Preferably, the atomization pressure is 0.01-0.1 MPa; Preferably, an oxidizing gas is used as the first carrier gas to spray the atomized mixed salt solution. The flow rate of the first carrier gas is 0.1-1 m / s and the pressure is 0.05-1 MPa.

6. The method according to claim 4 or 5, characterized in that, In step (1), T1 is 600-800℃; Preferably, the duration of the first heat treatment is 3-30 seconds; Preferably, the first heat treatment is carried out in an oxidizing atmosphere, which is preferably air and / or oxygen.

7. The method according to any one of claims 4-6, characterized in that, In step (2), T2 is 700-1100℃; Preferably, the second heat treatment time is 5-15 hours.

8. The method according to any one of claims 4-7, characterized in that, In step (2), the powder is fluidized using a second carrier gas, which is an oxygen-containing atmosphere; Preferably, the flow rate of the second carrier gas is 0.5-10 m / s; Preferably, the fluidized bed has a bed filling rate of 20%-70% in the fluidized state; Preferably, the pressure drop of the fluidized bed in the fluidized state is 0.01-0.05 MPa.

9. A cathode material prepared by the method according to any one of claims 4-8.

10. The application of the cathode material according to any one of claims 1-3 and 9 in a sodium-ion battery.

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