A high-rate sodium-ion secondary battery cathode material

Abstract

The present invention provides a high-rate sodium ion secondary battery positive electrode material, which belongs to the technical field of secondary battery materials. The chemical formula of the positive electrode material is Na x E y Mn g M d O2; where E element is an element with electronegativity satisfying EN≤1.2 and 0.5≤r E / r O One to three elements with electronegativity of 1.2≤EN≤2.0 and 0.34≤r M / r O One to six elements with a valence of ≤0.85, at least one of which has a valence of +2 or +3. This invention addresses the problems of existing layered oxide sodium-ion battery cathode materials with an O3 structure. The resulting cathode material exhibits minimal phase transitions and exhibits a single discharge voltage plateau when discharged below 3V. It also exhibits excellent rate performance, with a 5C / 0.2C discharge ratio of ≥80%. Industrial production is simple, making it ideal for high-rate applications such as power tools, electric ships, and electric heavy trucks.

Description

Technical Field

[0001] The present invention relates to the technical field of secondary battery materials, and in particular to a high-rate sodium ion secondary battery positive electrode material. Background Art

[0002] Lithium-ion batteries, with their advantages of high operating voltage, high energy density, and excellent cycle performance, have been widely used in numerous fields, including digital devices, power tools, drones, and new energy vehicles. However, in recent years, lithium ore prices have skyrocketed. my country's relatively scarce lithium resources have led to rising prices for lithium sources (such as lithium carbonate and lithium hydroxide), keeping lithium battery costs high. my country has abundant sodium resources, and the cost of sodium salts is negligible compared to lithium salts. Therefore, driven by cost reduction, sodium-ion batteries have garnered widespread attention, with the cathode material being the core material of sodium-ion batteries.

[0003] The main cathode materials for sodium-ion batteries include tunnel oxides, Prussian oxides, and layered oxides. Tunnel oxides offer good rate performance and are stable in air, but they also have lower capacity. Prussian oxides are low-cost and stable, but they face difficulties controlling the coordinated water during preparation. Layered oxides include P2 and O3 structures. P2 layered oxides offer good cycle stability but lower capacity.

[0004] Layered oxides with an O3 structure offer high capacity and a wide range of applications. However, despite this potential, they still suffer from significant shortcomings, primarily manifested in numerous phase transitions, structural instability, and rapid capacity decay. Therefore, a high-rate sodium-ion secondary battery cathode material is needed to address these existing challenges. Summary of the Invention

[0005] In view of this, the present invention provides a high-rate sodium ion secondary battery positive electrode material, which can solve the problems existing in the existing O3 structure layered oxide sodium ion battery positive electrode material. The prepared positive electrode material has less phase change and has only one discharge voltage platform when discharged to below 3V; it has excellent rate performance, with a 5C / 0.2C discharge ratio of ≥80%, simple industrial production, and is very suitable for high-rate application markets such as power tools, electric ships, and electric heavy trucks.

[0006] To achieve the above objectives, the present invention provides a high-rate sodium ion secondary battery cathode material, which adopts the following technical solution:

[0007] A high-rate sodium ion secondary battery cathode material, wherein the cathode material is charged and discharged under the conditions of a voltage of 2.0 to 4.0 V and a discharge rate of 0.1 C. When discharged to below 3 V, there is only one discharge voltage platform, and the 5C / 0.2C discharge ratio is ≥80%. The general chemical formula of the cathode material is Na xE y Mn g M d O2; where E is the electronegativity that satisfies EN≤1.2 and is 2- The ionic radius ratio satisfies 0.5≤r E / r O ≤1.0, E contains at least one and no more than three types of elements; 0.80≤x+y≤1.00, 0.80≤x<1.00, 0≤y<0.2; M is an electronegativity that satisfies 1.2≤EN≤2.0 and is compatible with O 2- The ionic radius ratio satisfies 0.34≤r M / r O ≤0.85, M contains at least one and no more than six element species, and contains at least one element with a valence of +2 or +3.

[0008] Furthermore, the positive electrode material has an O3-type layered structure, belongs to the R3m space group, and in the XRD spectrum, the interplanar spacing d(003) of the "003" peak is Na The interplanar spacing with the “006” peak d(006) Na The ratio d(003) Na / d(006) Na The range is 1.95~2.05; the interplanar spacing d(003) of the “003” peak Na The interplanar spacing with the "110" peak position d(110) Na The ratio d(003) Na / d(110) Na The range is 3.5 to 3.9.

[0009] Furthermore, the particle size distribution of the positive electrode material measured by a laser particle size analyzer has a median particle size D50 of 4 to 12 μm, and an equivalent specific surface area BET 等效 With D 10 The ratio satisfies (BET 等效 / D 10 ) is 0.10~1.20m 2 / (g*μm), equivalent specific surface area BET 等效 With D 90 The ratio satisfies (BET 等效 / D 90 ) is 0.02~0.40m 2 / (g*μm), equivalent specific surface area BET 等效 It is the specific surface area calculated based on the spherical surface area according to the equivalent diameter of the powder in the particle size test using a laser particle size analyzer.

[0010] Furthermore, M includes at least one and no more than six of Ni, Co, Fe, Cu, Al, Ti, Zr, W, Mo, Ce, Nb, B, Ce, and Si.

[0011] Furthermore, g≤0.6, when M is one element, g+d=1; when M is two or more elements, g+∑(dm n )=1,m n is the molar percentage of the nth element, where n is an integer from 1 to 6.

[0012] A method for preparing the above-mentioned high-rate sodium ion secondary battery positive electrode material comprises the following steps:

[0013] S1, containing Na + The solution and the hydroxide precursor are put into a vacuum dryer for mixing and drying. Under stirring conditions, the slurry containing E is added, and stirring and drying are continued to reduce the moisture content to below 0.5%, thereby obtaining powder 1.

[0014] S2, heat-treating the powder 1 obtained in S1 in an atmosphere containing O2 to obtain powder 2;

[0015] S3. The powder obtained in S2 is calcined at high temperature in an atmosphere containing O2 to obtain a bulk material, and the bulk material is crushed to obtain the positive electrode material.

[0016] Furthermore, in S1, the vacuum dryer is an integrated mixing and drying device having the capabilities of stirring and vacuum drying.

[0017] Furthermore, in S1, the Na-containing + The ratio of solution to hydroxide precursor is Na + The molar ratio of the hydroxide precursor (N Na / N 前驱体 ) is 0.7~1.1.

[0018] Preferably, (N Na / N 前驱体 ) is 0.9~1.0.

[0019] Furthermore, in S1, the Na-containing + The anion of the solution is an anion that can be decomposed into gas at ≥300℃, selected from CO3 2- OH - 、HCO3 - 、CHOO - or CH3COO - One of them.

[0020] Preferably, the Na-containing +The anion of the solution is an anion that can be decomposed into gas at ≥300℃, selected from CO3 2- or OH - .

[0021] Furthermore, in S1, the slurry containing E is an oxide or can be generated into an oxide by high temperature decomposition, and its general formula is A a B b C c R r ; Wherein, A, B and C are selected from one of Li, K, Rb, Cs, Mg, Ca, Sr, Ba, Y, La, R is an O atom or an anion that can be decomposed into a gas at ≥300°C, selected from CO3 2- OH - 、HCO3 - 、CHOO - 、CH3COO - One of them; r satisfies aV A +bV B +cV C +rV R =0, where, 0≤a≤1.0, 0≤b≤1.0, 0≤c≤1.0, y(aV A +bV B +cV C )≤x,V A 、V B 、V C and V R are the valences of elements A, B, C and anion R respectively.

[0022] Furthermore, in S1, the stirring speed is controlled by the stirring blade linear velocity v, v = 0.5 ~ 3.5 m / s.

[0023] Preferably, in S1, the stirring speed is controlled by the stirring blade linear velocity v, v = 1.5 ~ 2.5 m / s.

[0024] Furthermore, in S1, the vacuum degree is ≤-0.04 MPa.

[0025] Preferably, in order to shorten the operation time, the vacuum degree is ≤-0.06MPa.

[0026] Furthermore, in S1, the temperature is 60-120°C.

[0027] Preferably, in order to shorten the operation time, the temperature is 90-120°C.

[0028] Furthermore, in S2, the O2 concentration in the O2-containing atmosphere is ≥18% (volume ratio).

[0029] Preferably, in order to reduce manufacturing costs, the O2-containing atmosphere is an air atmosphere.

[0030] Furthermore, in S2, the temperature of the heat treatment is 300-800°C.

[0031] Preferably, the temperature of the heat treatment is 400-600°C.

[0032] Furthermore, in S2, the heat treatment time is 2-15 hours.

[0033] Preferably, the heat treatment time is 4-10 hours.

[0034] Furthermore, in S3, the O2 concentration in the O2-containing atmosphere is ≥18% (volume ratio).

[0035] Preferably, in order to reduce manufacturing costs, the O2-containing atmosphere is an air atmosphere.

[0036] Furthermore, in S3, the temperature of the high-temperature calcination is 600-1100°C.

[0037] Preferably, the temperature of the high-temperature calcination is 700-1000°C.

[0038] Furthermore, in S3, the high-temperature calcination time is 3-20 hours.

[0039] Preferably, the high-temperature calcination time is 6-12 hours.

[0040] The above technical solution of the present invention includes at least the following beneficial effects:

[0041] 1. The high-rate sodium-ion secondary battery cathode material provided by the present invention has the advantages of less phase change, stable structure, high initial efficiency and capacity, and excellent rate performance. It is very suitable for high-rate application markets such as power tools, electric ships, and electric heavy trucks;

[0042] 2. The preparation method of the high-rate sodium ion secondary battery positive electrode material provided by the present invention has the advantages of simple process and short manufacturing process. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 The first cycle charge and discharge curves of Example 1 and the comparative example are shown;

[0044] Figure 2 is the XRD pattern of Example 1;

[0045] Figure 3 is the SEM image of Example 1;

[0046] Figure 4 is the SEM image of Example 2;

[0047] Figure 5 This is the SEM image of Example 3;

[0048] Figure 6 This is the SEM image of Example 4. DETAILED DESCRIPTION

[0049] To make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the following will be combined with the appended drawings of the embodiments of the present invention. Figure 1-6 , clearly and completely describing the technical solutions of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the described embodiments of the present invention, all other embodiments derived by ordinary technicians in this field fall within the scope of protection of the present invention.

[0050] Example 1

[0051] A high-rate sodium-ion secondary battery cathode material Na 0.95 Sr 0.05 Mn 0.34 (FeNi) 0.33 The preparation method of O2, the specific steps are as follows:

[0052] (1) Press N Na :N Sr :N 前驱体 =0.95:0.05:1 (molar ratio) NaOH solution, SrCO3 powder, precursor [Mn 0.34 (FeNi) 0.33 (OH)2] was added to a vacuum mixing dryer, stirring was started, the stirring blade linear speed v = 0.8 m / s, the vacuum degree was -0.06 MPa, and the mixture was mixed and dried at 105°C to a moisture content of 0.4% (mass ratio), which was recorded as powder 1.

[0053] (2) Powder 1 is placed in a rotary kiln, air is introduced, and heat treated at 500°C for 4 hours to obtain powder 2.

[0054] (3) The powder was loaded into a sagger and air was blown into the roller kiln. The roller kiln was pushed at a speed of 1.5 m / h and kept at a constant temperature of 910 ° C for 10 hours. Then, it was cooled to below 150 ° C and crushed to obtain the positive electrode material Na 0.95 Sr 0.05 Mn 0.34 (FeNi) 0.33 O2.

[0055] The cathode material Na 0.95 Sr 0.05 Mn 0.34 (FeNi) 0.33 The SEM image of O2 is as follows Figure 3 shown.

[0056] (4) Particle size test: add 15 ml of sodium hexametaphosphate solution (concentration 2% by mass) to a 20 ml measuring cup, add 2 g of powder to the measuring cup, stir thoroughly, and then add the slurry to the wet sampler of the Malvern laser particle size analyzer with a dropper. The instrument shading degree is controlled within the range of 10%-11%, the internal ultrasonic intensity is 75%, and the powder particle size distribution is obtained by automatic continuous testing 3 times. 50 9.0μm, BET 等效 / D 10 =0.8, BET 等效 / D 90 =0.2.

[0057] (5) XRD test: After grinding, the positive electrode sample was sieved through a 325-mesh ultrasonic vibrating sieve. The sieve was taken and the test sample was prepared by the tableting method. Test conditions: voltage 40kV, tube current 40mA, scanning range 10-80℃, scanning speed 2° / min, step size 0.02°. The sample d(003) Na / d(006) Na =2.01,d(003) Na / d(110) Na =3.75.

[0058] XRD patterns such as Figure 2 shown.

[0059] (6) Electrical performance test: The above Na 0.95 Sr 0.05 Mn 0.34 (FeNi) 0.33 The O2 positive electrode material, conductive agent Super P, and binder PVDF were weighed in a weight ratio of 90:5:5, mixed evenly, and then NMP was added. The mixture was vacuum stirred in a degassing machine for 30 minutes to prepare a slurry. Aluminum foil was used as the current collector for coating, a metal sodium sheet was used as the negative electrode, and 1.0 mol / L NaPF6 / (EC+DEC) (1:1 Vol.) was used as the electrolyte. The CR2032 button battery was assembled in an argon-filled glove box. The capacity and rate performance of the above-mentioned CR2032 button battery were tested on a charge and discharge instrument, wherein the charge and discharge voltage range was 2.0-4.0V, the 0.1C first discharge capacity was 137.3mAh / g, the first efficiency was 94.5%, and the 5C / 0.2C discharge ratio was 84.6%.

[0060] Example 2

[0061] A high-rate sodium-ion secondary battery cathode material Na 0.83 Li 0.05 Mn 0.50 (Fe 0.98 Ni0.98 Zr 0.04 ) 0.25 The preparation method of O2, the specific steps are as follows:

[0062] (1) Press N Na :N Li :N 前驱体 =0.83:0.05:1 (molar ratio) NaOH solution, LiOH powder, precursor [Mn 0.50 (Fe 0.98 Ni 0.98 Zr 0.04 ) 0.25 (OH)2] was added to a vacuum mixing dryer, stirring was started, the stirring blade linear speed v = 0.7 m / s, the vacuum degree was -0.07 MPa, and the mixture was mixed and dried at 105°C to a moisture content of 0.4% (mass ratio), which was recorded as powder 1.

[0063] (2) Powder 1 was heat treated at 530°C for 3.5 h in a rotary kiln with air introduced to obtain powder 2.

[0064] (3) The powder was loaded into a sagger and air was blown into the roller kiln. The roller kiln was pushed at a speed of 1.6 m / h and kept at 930 ° C for 10 hours. After cooling to below 150 ° C, the positive electrode material Na was obtained by crushing. 0.83 Li 0.05 Mn 0.50 (Fe 0.98 Ni 0.98 Zr 0.04 ) 0.25 O2.

[0065] The cathode material Na 0.83 Li 0.05 Mn 0.50 (Fe 0.98 Ni 0.98 Zr 0.04 ) 0.25 The SEM image of O2 is as follows Figure 4 shown.

[0066] (4) Particle size test: add 15 ml of sodium hexametaphosphate solution (concentration 2% by mass) to a 20 ml measuring cup, add 2 g of powder to the measuring cup, stir thoroughly, and then add the slurry to the wet sampler of the Malvern laser particle size analyzer with a dropper. The instrument shading degree is controlled within the range of 10%-11%, the internal ultrasonic intensity is 75%, and the powder particle size distribution is obtained by automatic continuous testing 3 times. 50 8.8μm, BET 等效 / D 10 =1.1, BET 等效 / D 90 =0.3.

[0067] (5) XRD test: After grinding, the positive electrode sample was sieved through a 325-mesh ultrasonic vibrating sieve. The sieve was taken and the test sample was prepared by the tableting method. Test conditions: voltage 40kV, tube current 40mA, scanning range 10-80℃, scanning speed 2° / min, step size 0.02°. The sample d(003) Na / d(006) Na =1.99,d(003) Na / d(110) Na =3.79.

[0068] (6) Electrical performance test: The above Na 0.95 Sr 0.05 Mn 0.34 (FeNi) 0.33 The O2 positive electrode material, conductive agent Super P, and binder PVDF were weighed in a weight ratio of 90:5:5, mixed evenly, and then NMP was added. The mixture was vacuum stirred in a degassing machine for 30 minutes to prepare a slurry. Aluminum foil was used as the current collector for coating, a metal sodium sheet was used as the negative electrode, and 1.0 mol / L NaPF6 / (EC+DEC) (1:1 Vol.) was used as the electrolyte. The CR2032 button battery was assembled in an argon-filled glove box. The capacity and rate performance of the above-mentioned CR2032 button battery were tested on a charge and discharge instrument, wherein the charge and discharge voltage range was 2.0-4.0V, the 0.1C first discharge capacity was 130.5mAh / g, the first efficiency was 94.7%, and the 5C / 0.2C discharge ratio was 85.9%.

[0069] Example 3

[0070] A high-rate sodium-ion secondary battery cathode material Na 0.90 Mg 0.02 Mn 0.25 (Fe 1.175 Ni 1.175 Cu 0.15 ) 0.3 The preparation method of O2, the specific steps are as follows:

[0071] (1) Press N Na :N Mg :N 前驱体 =0.90:0.02:1 (molar ratio) NaOH solution, Mg(OH)2 powder, precursor [Mn 0.25 (Fe 1.175 Ni 1.175 Cu 0.15 ) 0.3(OH)2] was added to a vacuum mixing dryer, stirring was started, the stirring blade linear speed v = 0.8 m / s, the vacuum degree was -0.06 MPa, and the mixture was mixed and dried at 105°C to a moisture content of 0.4% (mass ratio), which was recorded as powder 1.

[0072] (2) Powder 1 is heat-treated in a rotary kiln at 600°C for 3 h with air introduced to obtain powder 2.

[0073] (3) The powder was loaded into a sagger and air was blown into the roller kiln. The roller kiln was pushed at a speed of 1.5 m / h and kept at a constant temperature of 880 ° C for 11 hours. After cooling to below 150 ° C, the positive electrode material Na was obtained by crushing. 0.90 Mg 0.02 Mn 0.25 (Fe 1.175 Ni 1.175 Cu 0.15 ) 0.3 O2.

[0074] The cathode material Na 0.90 Mg 0.02 Mn 0.25 (Fe 1.175 Ni 1.175 Cu 0.15 ) 0.3 The SEM image of O2 is as follows Figure 5 shown.

[0075] (4) Particle size test: add 15 ml of sodium hexametaphosphate solution (concentration 2% by mass) to a 20 ml measuring cup, add 2 g of powder to the measuring cup, stir thoroughly, and then add the slurry to the wet sampler of the Malvern laser particle size analyzer with a dropper. The instrument shading degree is controlled within the range of 10%-11%, the internal ultrasonic intensity is 75%, and the powder particle size distribution is obtained by automatic continuous testing 3 times. 50 8.0μm, BET 等效 / D 10 =0.4, BET 等效 / D 90 =0.1.

[0076] (5) XRD test: After grinding, the positive electrode sample was sieved through a 325-mesh ultrasonic vibrating sieve. The sieve was taken and the test sample was prepared by the tableting method. Test conditions: voltage 40kV, tube current 40mA, scanning range 10-80℃, scanning speed 2° / min, step size 0.02°. The sample d(003) Na / d(006) Na =2.02, d(003) Na / d(110) Na =3.60.

[0077] (6) Electrical performance test: The above Na0.90 Mg 0.02 Mn 0.25 (Fe 1.175 Ni 1.175 Cu 0.15 ) 0.3 The O2 positive electrode material, conductive agent Super P, and binder PVDF were weighed in a weight ratio of 90:5:5, mixed evenly, and then NMP was added. The mixture was vacuum stirred in a degassing machine for 30 minutes to prepare a slurry. Aluminum foil was used as the current collector for coating, a metal sodium sheet was used as the negative electrode, and 1.0 mol / L NaPF6 / (EC+DEC) (1:1 Vol.) was used as the electrolyte. The CR2032 button battery was assembled in an argon-filled glove box. The capacity and rate performance of the above-mentioned CR2032 button battery were tested on a charge and discharge instrument, wherein the charge and discharge voltage range was 2.0-4.0V, the 0.1C first discharge capacity was 145.7mAh / g, the first efficiency was 93.5%, and the 5C / 0.2C discharge ratio was 86.1%.

[0078] Example 4

[0079] A high-rate sodium-ion secondary battery cathode material Na 0.96 La 0.02 Mn 0.25 (Fe 1.175 Ni 1.175 Cu 0.15 ) 0.3 The preparation method of O2, the specific steps are as follows:

[0080] (1) Press N Na :N La :N 前驱体 =0.90:0.02:1 (molar ratio) NaOH solution, La2O3 powder, precursor [Mn 0.25 (Fe 1.175 Ni 1.175 Cu 0.15 ) 0.3 (OH)2] was added to a vacuum mixing dryer, stirring was started, the stirring blade linear speed v = 0.8 m / s, the vacuum degree was -0.06 MPa, and the mixture was mixed and dried at 105°C to a moisture content of 0.4% (mass ratio), which was recorded as powder 1.

[0081] (2) Powder 1 is heat-treated in a rotary kiln at 600°C for 3 h with air introduced to obtain powder 2.

[0082] (3) The powder was loaded into a sagger and air was blown into the roller kiln. The roller kiln was pushed at a speed of 1.5 m / h and kept at a constant temperature of 880 ° C for 11 hours. After cooling to below 150 ° C, the positive electrode material Na was obtained by crushing. 0.90 Mg 0.02 Mn0.25 (Fe 1.175 Ni 1.175 Cu 0.15 ) 0.3 O2.

[0083] The cathode material Na 0.90 Mg 0.02 Mn 0.25 (Fe 1.175 Ni 1.175 Cu 0.15 ) 0.3 The SEM image of O2 is as follows Figure 6 shown.

[0084] (4) Particle size test: add 15 ml of sodium hexametaphosphate solution (concentration 2% by mass) to a 20 ml measuring cup, add 2 g of powder to the measuring cup, stir thoroughly, and then add the slurry to the wet sampler of the Malvern laser particle size analyzer with a dropper. The instrument shading degree is controlled within the range of 10%-11%, the internal ultrasonic intensity is 75%, and the powder particle size distribution is obtained by automatic continuous testing 3 times. 50 9.8μm, BET 等效 / D 10 =1.0, BET 等效 / D 90 =0.25.

[0085] (5) XRD test: After grinding, the positive electrode sample was sieved through a 325-mesh ultrasonic vibrating sieve. The sieve was taken and the test sample was prepared by the tableting method. Test conditions: voltage 40kV, tube current 40mA, scanning range 10-80℃, scanning speed 2° / min, step size 0.02°. The sample d(003) Na / d(006) Na =2.02, d(003) Na / d(110) Na =3.85.

[0086] (6) Electrical performance test: The above Na 0.90 Mg 0.02 Mn 0.25 (Fe 1.175 Ni 1.175 Cu 0.15 ) 0.3The O2 positive electrode material, conductive agent Super P, and binder PVDF were weighed in a weight ratio of 90:5:5, mixed evenly, and then NMP was added. The mixture was vacuum stirred in a degassing machine for 30 minutes to prepare a slurry. Aluminum foil was used as the current collector for coating, a metal sodium sheet was used as the negative electrode, and 1.0 mol / L NaPF6 / (EC+DEC) (1:1 Vol.) was used as the electrolyte. The CR2032 button battery was assembled in an argon-filled glove box. The capacity and rate performance of the above-mentioned CR2032 button battery were tested on a charge and discharge instrument, wherein the charge and discharge voltage range was 2.0-4.0V, the 0.1C first discharge capacity was 143.1mAh / g, the first efficiency was 93.9%, and the 5C / 0.2C discharge ratio was 84.9%.

[0087] Comparative Example

[0088] A positive electrode material Na 0.95 Ni 0.33 Fe 0.33 Mn 0.34 The preparation method of O2, the specific steps are as follows:

[0089] (1) Sodium carbonate (Na2CO3), precursor [Ni 0.33 Fe 0.33 Mn 0.34 (OH)2] was put into a high-speed mixer and mixed uniformly at 150 r / min×2 min and 500 r / min×20 min to obtain powder 1.

[0090] (2) Once the powder is loaded into the sagger, press 300 Nm 3 / h to introduce blast air into the roller, the roller kiln push speed is 1.8m / h, the temperature is kept constant at 920℃ for 10h, the total reaction time is 24h, and the positive electrode material Na is obtained by crushing. 0.95 Ni 0.33 Fe 0.33 Mn 0.34 O2.

[0091] (3) Particle size test: Add 15 ml of sodium hexametaphosphate solution (concentration 2% by mass) to a 20 ml measuring cup, add 2 g of powder (precursor or cathode material) to the measuring cup, stir thoroughly, and then use a dropper to add the slurry to the wet sampler of the Malvern laser particle size analyzer. The instrument shading degree is controlled within the range of 10%-11%, the internal ultrasonic intensity is 75%, and the powder particle size distribution is obtained by automatic continuous testing 3 times. The above-mentioned precursor D 50 12.0 μm, BET 等效 / D 10 =1.3, BET 等效 / D 90 =0.5.

[0092] (4) Electrical performance test: The above LiNi 0.50 Co 0.20 Mn 0.29 Al 0.01 O2 positive electrode material is used as the positive electrode material of lithium-ion batteries, SP is a conductive agent, and PVDF is a binder. The positive electrode material, conductive agent, and binder are weighed separately at a weight ratio of 90:5:5, mixed evenly, and then a slurry is prepared. Aluminum foil is used as the current collector for coating, a metal sodium sheet is used as the negative electrode, and 1.0 mol / L NaPF6 / (EC+DEC) (1:1 Vol.) is used as the electrolyte. CR2032 button cells are assembled in an argon-filled glove box. The above-mentioned CR2032 button cell was tested for capacity and rate performance on a charge and discharge instrument, wherein the charge and discharge voltage range is 2.0-4.0V, the 0.1C first discharge capacity is 120.7mAh / g, the first efficiency is 87.9%, and the 5C / 0.2C discharge ratio is 64.1%.

[0093] Table 1. Battery performance of positive electrode materials of Examples 1-4 and Comparative Examples

[0094]

[0095] As shown in Table 1, which lists the comparative results of the gram capacity and rate performance of Examples 1-4 and the comparative example, Example 1 has a capacity nearly 10 mAh / g higher than the comparative example, a 7% higher first efficiency, and a 19.5% higher 5C / 0.2C discharge ratio.

[0096] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A high-rate sodium ion secondary battery cathode material, characterized in that: The general chemical formula of the positive electrode material is Na x E y Mn g M d O2; Among them, E element is an element with electronegativity satisfying EN≤1.2 and 0.5≤r E / r O One to three elements among those with a value of ≤1.0; Among them, 0.80≤x+y≤1.00, 0.80≤x<1.00, 0<y<0.2; Among them, the M element is an element with electronegativity satisfying 1.2≤EN≤2.0 and 0.34≤r M / r O One to six elements with a valence of ≤0.85, at least one of which has a valence of +2 or +3; The positive electrode material preparation process includes the following steps: S1, containing Na + The solution and the hydroxide precursor are put into a vacuum dryer for mixing and drying. Under stirring conditions, add the slurry containing E, continue stirring and drying until the moisture content is reduced to below 0.5% to obtain powder 1; S2, heat-treating the powder 1 obtained in S1 in an atmosphere containing O2 to obtain powder 2; the heat-treating temperature is 300-800°C; the heat-treating time is 2-15h; S3, calcining the powder obtained in S2 in an atmosphere containing O2 at high temperature to obtain a bulk material, and crushing the bulk material to obtain the positive electrode material; the high temperature calcination temperature is 600-1100°C; the high temperature calcination time is 3-20h; In S1, the slurry containing E is an oxide or can be generated into an oxide by high temperature decomposition, and its general formula is A a B b C c R r A, B and C are all selected from K, Ca, Sr, Ba and La, R is an O atom or an anion that can be decomposed into a gas at ≥300℃, selected from CO3 2- OH - 、HCO3 - 、CHOO - 、CH3COO - One of the following; r satisfies aV A +bV B +cV C +rV R =0, where, 0<a≤1.0, 0≤b≤1.0, 0≤c≤1.0, y (aV A +bV B +cV C )≤x,V A 、V B 、V C and V R are the valences of elements A, B, C and anion R respectively; M includes at least one and no more than six of Co, Cu, Al, Ti, Zr, and Nb; The positive electrode material has an O3 type layered structure and belongs to the R3m space group. In the XRD spectrum, the interplanar spacing d(003) of the "003" peak is Na Interplanar spacing with the "006" peak d(006) Na The ratio d(003) Na / d(006) Na The range is 1.95~2.05; the interplanar spacing d(003) at the "003" peak Na Interplanar spacing d(110) with the "110" peak Na The ratio d(003) Na / d(110) Na The range is 3.5~3.9; The median particle size D50 of the positive electrode material is 4-12 μm, and the equivalent specific surface area BET 等效 With D 10 The ratio satisfies BET 等效 / D 10 0.10~1.20m 2 / (g*μm), equivalent specific surface area BET 等效 With D 90 The ratio satisfies BET 等效 / D 90 0.02~0.40m 2 / (g*μm).

2. The high-rate sodium ion secondary battery cathode material according to claim 1, wherein g≤0.6, when M is one element, g+d=1; when M is a combination of two to six elements, n is the number of element types, g+∑(dm n )=1,m n is the mole percentage of the nth element.

3. The high-rate sodium ion secondary battery cathode material according to claim 1, wherein In S1, the vacuum dryer is an integrated mixing and drying device with the capabilities of stirring and vacuum drying.

4. The high-rate sodium ion secondary battery cathode material according to claim 1, wherein In S1, the Na + The anion of the solution is an anion that can be decomposed into gas at ≥300℃, selected from CO3 2- OH - 、HCO3 - 、CHOO - or CH3COO - One of them.

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