A P2-type sodium-ion battery cathode material and preparation method

Abstract

The present invention provides a cathode material for a P2-type sodium-ion battery and a preparation method thereof. The cathode material for the P2-type sodium-ion battery of the present invention has a core-shell structure and includes Na a Ni x Mn 2x Gd y Ba z O2 material and a conductor coating layer coated on the surface of the matrix core material. The conductor coating layer material is a mixture of Ti(HPO4)2 and MgHPO4, wherein 0.6 ≤ a ≤ 0.7, 0.005 ≤ y ≤ 0.02, 0.001 ≤ z ≤ 0.01, and 3x + y + z = 1 is satisfied. The present invention has excellent rate performance and cycling performance at high voltages for the cathode material of the P2-type sodium-ion battery.

Description

Technical Field

[0001] The present invention relates to the field of battery materials, and particularly to a P2-type sodium-ion battery cathode material and a preparation method thereof. Background Art

[0002] Sodium-ion batteries based on P2-type cathode materials have become the most potential substitutes for lithium-ion batteries or lead-acid batteries in high-power fields such as start-stop power supplies due to their environmental friendliness, over-discharge tolerance, excellent high and low temperature performance, and rate performance. Although the P2-type sodium-ion battery cathode material has excellent cycling performance under conventional voltages, its capacity is relatively low; when the upper limit voltage is increased to more than 4.2V, although such materials have considerable capacity and median voltage, the irreversible phase transition from P2 phase to O2 phase results in poor cycle stability. Although the rate performance of P2-type materials is better than that of O3-type materials, the rate performance at high voltages still needs to be further improved. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a P2-type sodium-ion battery cathode material and a preparation method thereof, a sodium-ion battery cathode material with Gd / Ba double doping and composite fast ion conductor coating, which has excellent rate performance and cycle performance at high voltages and is expected to be applied in high-power fields such as start-stop power supplies and electric tools.

[0004] To achieve the above purpose, the technical solution adopted by the present invention is: a P2-type sodium-ion battery cathode material, the P2-type sodium-ion battery cathode material has a core-shell structure, including Na as the matrix core a Ni x Mn 2x Gd y Ba z O 2 material and a conductor coating layer coated on the surface of the matrix core material, the conductor coating layer material is a mixture of Ti(HPO 4 ) 2 and MgHPO 4 , where 0.6 ≤ a ≤ 0.7, 0.005 ≤ y ≤ 0.02, 0.001 ≤ z ≤ 0.01, and 3x + y + z = 1.

[0005] The above P2-type sodium-ion battery cathode material has a core-shell structure, the core material uses Gd / Ba double doping at the same time, with Na a Ni x Mn 2x Gd y Ba z O 2 material as the matrix core, and at the same time, a conductor coating layer on the surface of the matrix core material, the conductor coating layer material is Ti(HPO 4) 2 and MgHPO 4 The mixture of, through the coating material Ti(HPO 4 ) 2 and MgHPO 4 has excellent rate performance and cycling performance at high voltages.

[0006] Preferably, 0.65 ≤ a ≤ 0.68.

[0007] Preferably, in the P2-type sodium-ion battery cathode material, the coating material accounts for 0.1% to 1% of the mass of the P2-type sodium-ion battery cathode material.

[0008] The above P2-type sodium-ion battery cathode material has more excellent rate performance and cycling performance at high voltages.

[0009] Preferably, 1 ≤ y / z ≤ 2, 0.008 ≤ y ≤ 0.15.

[0010] The above P2-type sodium-ion battery cathode material has more excellent rate performance and cycling performance at high voltages.

[0011] Preferably, in the conductor coating material, the weight ratio of Ti(HPO 4 ) 2 and MgHPO 4 is (2 to 8):1.

[0012] For the above P2-type sodium-ion battery cathode material, when the weight ratio of Ti(HPO 4 ) 2 and MgHPO 4 in the conductor coating material is (2 to 8):1, it has more excellent rate performance and cycling performance at high voltages.

[0013] Preferably, in the conductor coating material, the weight ratio of Ti(HPO 4 ) 2 and MgHPO 4 is (3 to 5):1.

[0014] For the above P2-type sodium-ion battery cathode material, when the weight ratio of Ti(HPO 4 ) 2 and MgHPO 4 in the conductor coating material is (3 to 5):1, it has more excellent rate performance and cycling performance at high voltages.

[0015] The present invention also provides a preparation method of any one of the above P2-type sodium-ion battery cathode materials, and the method includes the following steps:

[0016] (1) Mix the sodium source, nickel source, manganese source, gadolinium source and barium source evenly according to the stoichiometric ratio and then conduct the first heat treatment to obtain the P2 matrix Na a Ni x Mn 2x Gd y Ba z O 2 ; The holding temperature of the first heat treatment is 850 °C to 1050 °C, the holding time is 8 to 16 hours, the heating rate is 3 to 5 °C / min, and the sintering atmosphere is air;

[0017] (2) Crush the Na a Ni x Mn 2x Gd y Ba z O 2 material obtained in step (1), and the particle size meets D00≥0.5μm, 4.0μm≤D50≤5.5μm, D100≤14μm;

[0018] (3) Mix the material obtained in step (2) with Ti(HPO 4 ) 2 , MgHPO 4 evenly according to the mass ratio and then conduct the second heat treatment to obtain the cathode material for a high-voltage and high-rate P2-type sodium-ion battery; for the second heat treatment, the holding temperature is 650 °C to 850 °C, the holding time is 4 to 10 hours, the heating rate is 3 to 5 °C / min, and the sintering atmosphere is air;

[0019] (4) Crush the material obtained in step (3), and the particle size meets D00≥0.6μm, 4.5μm≤D50≤6.5μm, D100≤16μm.

[0020] Preferably, the sodium source is one or more of sodium carbonate, sodium hydroxide and sodium oxalate.

[0021] Preferably, the nickel source is one or more of its oxides, oxalates or hydroxides.

[0022] Preferably, the manganese source and gadolinium source are their corresponding oxides.

[0023] Preferably, the barium source is one or two of its carbonates and oxalates.

[0024] The present invention also provides a secondary sodium-ion battery, and the secondary sodium-ion battery includes the cathode material for a P2-type sodium-ion battery described above.

[0025] The beneficial effects of the present invention are as follows: The present invention provides a cathode material for a P2-type sodium-ion battery and a preparation method thereof. The cathode material for the P2-type sodium-ion battery of the present invention has a core-shell structure. The core material uses Gd / Ba double doping at the same time, with Na a Ni x Mn 2x Gd y Ba z O 2 material as the matrix core. At the same time, a conductor coating layer is provided on the surface of the matrix core material. The conductor coating layer material is a mixture of Ti(HPO 4 ) 2 and MgHPO 4 . Through the mixed combination of the coating layer materials Ti(HPO 4 ) 2 and MgHPO 4 , it has excellent rate performance and cycling performance at high voltages. It is expected to be applied in high-power fields such as start-stop power supplies and electric tools.

[0026] The cathode material for the P2-type sodium-ion battery of the present invention has the following advantages:

[0027] 1) Ba has a relatively weak electronegativity and a relatively large ionic radius, which can effectively weaken the attraction of O 2- to Na + , thereby reducing the diffusion barrier of Na + and constructing a fast internal Na + channel.

[0028] 2) The high lattice energy between Gd and O (Gd—O, 716 kJ / mol) can effectively improve the stability of the crystal structure and inhibit the escape of oxygen at high voltages, thereby improving the cycling stability of the material.

[0029] 3) The surface-coated composite fast ion conductor can construct a fast Na + channel on the surface of the material, thereby improving the rate performance of the material. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the rate discharge curve of the cathode material for the P2-type sodium-ion battery in the embodiment of the present invention.

[0031] Figure 2 is the rate discharge curve of the cathode material for the P2-type sodium-ion battery in the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0032] To better illustrate the purpose, technical solution and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments.

[0033] Example 1

[0034] As a cathode material for a P2-type sodium-ion battery according to an embodiment of the present invention, the P2-type sodium-ion battery cathode material has a core-shell structure, including Na as the matrix core 0.67 Ni x Mn 2x Gd y Ba z O 2 material and a conductor coating layer coated on the surface of the matrix core material. The conductor coating layer material is a mixture of Ti(HPO 4 ) 2 and MgHPO 4 . Among them, 0.005 ≤ y ≤ 0.02, 0.001 ≤ z ≤ 0.01, and 3x + y + z = 1 is satisfied.

[0035] The preparation method of the P2-type sodium-ion battery cathode material in this embodiment includes the following steps:

[0036] S1. Weigh sodium carbonate, nickel oxide, manganese dioxide, gadolinium oxide, and barium carbonate in proportion to prepare Na 0.67 Ni 0.33 Mn 0.66 Gd 0.005 Ba 0.005 O 2 . After mixing all the raw materials evenly, keep them at 970 °C for 14 h, where the heating rate is 4 °C / min and the sintering atmosphere is air.

[0037] S2. The material obtained in S1 is successively crushed by jaw crusher, roll crusher, and air classifier. The D00 of the obtained material is 0.53 μm, D50 is 4.84 μm, and D100 is 12.42 μm.

[0038] S3. Weigh the material obtained in S2, Ti(HPO 4 ) 2 (TP), and MgHPO 4 (MP) in proportion to prepare Na 0.67 Ni 0.33 Mn 0.66 Gd 0.005 Ba 0.005 O 2 @0.4%TP&0.1%MP. The % in the formula means that when adding raw materials, Ti(HPO 4 ) 2 , MgHPO 4 account for Na 0.67 Ni 0.33 Mn 0.66 Gd 0.005 Ba 0.005 O 2@The theoretical content of 0.4% TP & 0.1% MP. After mixing all the raw materials evenly, keep them at 750 °C for 8 h. The heating rate is 3 °C / min and the sintering atmosphere is air;

[0039] S4. Crush the material obtained in S3 successively by jaw crusher, roll crusher and airflow mill. The D00 of the obtained material is 0.65 μm, D50 is 5.68 μm, and D100 is 15.34 μm.

[0040] Example 2

[0041] As a cathode material for P2-type sodium-ion batteries in an embodiment of the present invention.

[0042] The preparation method of the cathode material for P2-type sodium-ion batteries in this example includes the following steps:

[0043] S1. Weigh sodium carbonate, nickel oxide, manganese dioxide, gadolinium oxide, barium carbonate in proportion to prepare Na 0.67 Ni 0.328 Mn 0.656 Gd 0.01 Ba 0.006 O 2 . After mixing all the raw materials evenly, keep them at 970 °C for 14 h. The heating rate is 4 °C / min and the sintering atmosphere is air.

[0044] S2. Crush the material obtained in S1 successively by jaw crusher, roll crusher and airflow mill. The D00 of the obtained material is 0.55 μm, D50 is 4.88 μm, and D100 is 12.52 μm.

[0045] S3. Weigh the material obtained in S2, Ti(HPO 4 ) 2 (TP), MgHPO 4 (MP) in proportion to prepare Na 0.67 Ni 0.328 Mn 0.656 Gd 0.01 Ba 0.006 O 2 @0.4% TP & 0.1% MP. After mixing all the raw materials evenly, keep them at 750 °C for 8 h. The heating rate is 3 °C / min and the sintering atmosphere is air.

[0046] S4. Crush the material obtained in S3 successively by jaw crusher, roll crusher and airflow mill. The D00 of the obtained material is 0.68 μm, D50 is 5.71 μm, and D100 is 15.44 μm.

[0047] Example 3

[0048] As a cathode material for P2-type sodium-ion batteries in an embodiment of the present invention.

[0049] The preparation method of the cathode material of the P2-type sodium ion battery in this embodiment includes the following steps:

[0050] S1. Weigh sodium carbonate, nickel oxide, manganese dioxide, gadolinium oxide, and barium carbonate in proportion to prepare Na 0.67 Ni 0.321 Mn 0.642 Gd 0.03 Ba 0.007 O 2 . After mixing the raw materials evenly, keep them at 970 °C for 14 h. The heating rate is 4 °C / min, and the sintering atmosphere is air.

[0051] S2. The material obtained in S1 is successively subjected to jaw crushing, roll crushing, and air flow milling. The D00 of the obtained material is 0.57 μm, the D50 is 4.91 μm, and the D100 is 12.68 μm.

[0052] S3. Weigh the material obtained in S2, Ti(HPO 4 ) 2 (TP), and MgHPO 4 (MP) to prepare Na 0.67 Ni 0.321 Mn 0.642 Gd 0.03 Ba 0.007 O 2 @0.4% TP & 0.1% MP. After mixing the raw materials evenly, keep them at 750 °C for 8 h. The heating rate is 3 °C / min, and the sintering atmosphere is air.

[0053] S4. The material obtained in S3 is successively subjected to jaw crushing, roll crushing, and air flow milling. The D00 of the obtained material is 0.70 μm, the D50 is 5.74 μm, and the D100 is 15.49 μm.

[0054] Example 4

[0055] As a cathode material of the P2-type sodium ion battery in an embodiment of the present invention.

[0056] The preparation method of the cathode material of the P2-type sodium ion battery in this embodiment includes the following steps:

[0057] S1. Weigh sodium carbonate, nickel oxide, manganese dioxide, gadolinium oxide, and barium carbonate in proportion to prepare Na 0.67 Ni 0.314 Mn 0.628 Gd 0.05 Ba 0.008 O 2 . After mixing the raw materials evenly, keep them at 970 °C for 14 h. The heating rate is 4 °C / min, and the sintering atmosphere is air.

[0058] S2. Sequentially carry out jaw crushing, roll crushing, and airflow milling on the material obtained in S1. The D00 of the obtained material is 0.59 μm, the D50 is 4.95 μm, and the D100 is 12.71 μm.

[0059] S3. Weigh the material obtained in S2, Ti(HPO 4 ) 2 (TP), and MgHPO 4 (MP) in proportion to prepare Na 0.67 Ni 0.314 Mn 0.628 Gd 0.05 Ba 0.008 O 2 @0.4% TP & 0.1% MP. After mixing all raw materials evenly, keep them at 750 °C for 8 h. The heating rate is 3 °C / min, and the sintering atmosphere is air.

[0060] S4. Sequentially carry out jaw crushing, roll crushing, and airflow milling on the material obtained in S3. The D00 of the obtained material is 0.71 μm, the D50 is 5.77 μm, and the D100 is 15.61 μm.

[0061] Example 5

[0062] As a P2-type sodium-ion battery cathode material of an embodiment of the present invention.

[0063] The preparation method of the P2-type sodium-ion battery cathode material in this embodiment includes the following steps:

[0064] S1. Weigh sodium carbonate, nickel oxide, manganese dioxide, gadolinium oxide, and barium carbonate in proportion to prepare Na 0.67 Ni 0.328 Mn 0.656 Gd 0.01 Ba 0.006 O 2 . After mixing all raw materials evenly, keep them at 970 °C for 14 h. The heating rate is 4 °C / min, and the sintering atmosphere is air.

[0065] S2. Sequentially carry out jaw crushing, roll crushing, and airflow milling on the material obtained in S1. The D00 of the obtained material is 0.55 μm, the D50 is 4.88 μm, and the D100 is 12.52 μm.

[0066] S3. Weigh the material obtained in S2, Ti(HPO 4 ) 2 (TP), and MgHPO 4 (MP) in proportion to prepare Na 0.67 Ni 0.328 Mn 0.656 Gd 0.01 Ba0.006 O 2 @0.08% TP & 0.02% MP. After mixing all raw materials evenly, keep them at 750 °C for 8 h. The heating rate is 3 °C / min and the sintering atmosphere is air.

[0067] S4. Crush the material obtained in S3 successively by jaw crusher, roll crusher and air classifier. The D00 of the obtained material is 0.64 μm, D50 is 5.65 μm, and D100 is 15.24 μm.

[0068] Example 6

[0069] As a cathode material for P2-type sodium-ion batteries in an embodiment of the present invention.

[0070] The preparation method of the cathode material for P2-type sodium-ion batteries in this embodiment includes the following steps:

[0071] S1. Weigh sodium carbonate, nickel oxide, manganese dioxide, gadolinium oxide, barium carbonate in proportion to prepare Na 0.67 Ni 0.328 Mn 0.656 Gd 0.01 Ba 0.006 O 2 . After mixing all raw materials evenly, keep them at 970 °C for 14 h. The heating rate is 4 °C / min and the sintering atmosphere is air.

[0072] S2. Crush the material obtained in S1 successively by jaw crusher, roll crusher and air classifier. The D00 of the obtained material is 0.55 μm, D50 is 4.88 μm, and D100 is 12.52 μm.

[0073] S3. Weigh the material obtained in S2, Ti(HPO 4 ) 2 (TP), MgHPO 4 (MP) in proportion to prepare Na 0.67 Ni 0.328 Mn 0.656 Gd 0.01 Ba 0.006 O 2 @0.8% TP & 0.2% MP. After mixing all raw materials evenly, keep them at 750 °C for 8 h. The heating rate is 3 °C / min and the sintering atmosphere is air.

[0074] S4. Crush the material obtained in S3 successively by jaw crusher, roll crusher and air classifier. The D00 of the obtained material is 0.68 μm, D50 is 5.74 μm, and D100 is 15.68 μm.

[0075] Example 7

[0076] As a cathode material for a P2-type sodium-ion battery according to an embodiment of the present invention, the only difference between this embodiment and Embodiment 2 is that in the coating material, the content and ratio of Ti(HPO 4 ) 2 (TP) and MgHPO 4 (MP).

[0077] Na 0.67 Ni 0.328 Mn 0.656 Gd 0.01 Ba 0.006 O 2 @0.4% TP & 0.2% MP.

[0078] Example 8

[0079] As a cathode material for a P2-type sodium-ion battery according to an embodiment of the present invention, the only difference between this embodiment and Embodiment 2 is that in the coating material, the content and ratio of Ti(HPO 4 ) 2 (TP) and MgHPO 4 (MP).

[0080] Na 0.67 Ni 0.328 Mn 0.656 Gd 0.01 Ba 0.006 O 2 @0.45% TP & 0.15% MP.

[0081] Example 9

[0082] As a cathode material for a P2-type sodium-ion battery according to an embodiment of the present invention, the only difference between this embodiment and Embodiment 2 is that in the coating material, the content and ratio of Ti(HPO 4 ) 2 (TP) and MgHPO 4 (MP).

[0083] Na 0.67 Ni 0.328 Mn 0.656 Gd 0.01 Ba 0.006 O 2 @0.5% TP & 0.1% MP.

[0084] Example 10

[0085] As a cathode material for a P2-type sodium-ion battery according to an embodiment of the present invention, the only difference between this embodiment and Embodiment 2 is that in the coating material, the content and ratio of Ti(HPO 4 ) 2 (TP) and MgHPO4 (MP) content and ratio.

[0086] Na 0.67 Ni 0.328 Mn 0.656 Gd 0.01 Ba 0.006 O 2 @ 0.3% TP & 0.3% MP.

[0087] Example 11

[0088] As a P2-type sodium-ion battery cathode material according to an embodiment of the present invention, the only difference between this embodiment and Example 2 is that in the coating material, Ti(HPO 4 ) 2 (TP), MgHPO 4 (MP) content and ratio.

[0089] Na 0.67 Ni 0.328 Mn 0.656 Gd 0.01 Ba 0.006 O 2 @ 0.8% TP & 0.1% MP.

[0090] Comparative Example 1

[0091] As a P2-type sodium-ion battery cathode material according to a comparative example of the present invention, the difference between this comparative example and Example 2 is that there is no core-shell structure and no coating layer, and the chemical formula of the material is

[0092] Na 0.67 Ni 0.328 Mn 0.656 Gd 0.01 Ba 0.006 O 2 .

[0093] Comparative Example 2

[0094] As a P2-type sodium-ion battery cathode material according to a comparative example of the present invention, the difference between this comparative example and Example 2 is that the coating layer is Ti(HPO 4 ) 2 , the coating layer does not contain MgHPO 4 , and the amount of MgHPO 4 is made up by Ti(HPO 4 ) 2 . The chemical formula of the material is Na 0.67 Ni 0.328 Mn 0.656 Gd 0.01 Ba 0.006 O 2 @ 0.5% TP.

[0095] Comparative Example 3

[0096] As a cathode material for a P2-type sodium-ion battery in the comparative example of the present invention, the difference between this comparative example and Example 2 is that the coating layer is MgHPO 4 , and the coating layer does not contain Ti(HPO 4 ) 2 , and the amount of Ti(HPO 4 ) 2 is supplemented by MgHPO 4 . The chemical formula of the material is Na 0.67 Ni 0.328 Mn 0.656 Gd 0.01 Ba 0.006 O 2 @0.5% MP.

[0097] Comparative Example 4

[0098] As a cathode material for a P2-type sodium-ion battery in the comparative example of the present invention, the difference between this comparative example and Example 2 is that Gd is not doped, and the content of Gd is supplemented by Ba. The chemical formula of the material is Na 0.67 Ni 0.328 Mn 0.656 Ba 0.016 O 2 @0.4% TP & 0.1% MP.

[0099] Comparative Example 5

[0100] As a cathode material for a P2-type sodium-ion battery in the comparative example of the present invention, the difference between this comparative example and Example 2 is that Ba is not doped, and the content of Ba is supplemented by Gd. The chemical formula of the material is Na 0.67 Ni 0.328 Mn 0.656 Gd 0.016 O 2 @0.4% TP & 0.1% MP.

[0101] Experimental Method

[0102] Electrochemical Performance

[0103] The electrochemical performance was tested using a half-cell (2.0V - 4.25V), and the key parameters are as follows:

[0104] 1) Cathode material: acetylene black: PVDF = 85:10:5

[0105] 2) Anode: sodium sheet

[0106] 3) Electrolyte: 1.0 M NaPF6 (DEC:EC:EMC = 1:1:1, Vol% with 8% FEC)

[0107] The electrochemical performances of the cathode materials for P2-type sodium ion batteries in the examples and comparative examples are shown in Table 1.

[0108] Table 1 Electrochemical performances of the cathode materials for P2-type sodium ion batteries

[0109]

[0110]

[0111] As can be seen from Table 1, the cathode material for the P2-type sodium ion battery of the present invention has a core-shell structure. The core material uses Gd / Ba double doping simultaneously, with Na 0.67 Ni x Mn 2x Gd y Ba z O 2 material as the matrix core, and at the same time, a conductor coating layer on the surface of the matrix core material. The conductor coating layer material is a mixture of Ti(HPO 4 ) 2 and MgHPO 4 . Through the mixed combination of the coating layer materials Ti(HPO 4 ) 2 and MgHPO 4 , it has excellent rate performance and cycling performance at high voltages, and also improves the cycling performance under high-temperature conditions.

[0112] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A P2 type sodium ion battery positive electrode material, characterized in that: The P2 type sodium ion battery positive electrode material is a core-shell structure, including Na a Ni x Mn 2x G y Ba z O2 material and a conductor coating layer coated on the surface of the matrix core material, the conductor coating layer material is a product of heat treatment of a mixture of Ti(HPO4)2 and MgHPO4 at a holding temperature of 650°C~850°C, wherein 0.6≤a≤0.7, 0.005≤y≤0.02, 0.001≤z≤0.01, and 3x+y+z=1 is satisfied, and the coating layer material accounts for 0.1%~1% of the mass of the P2 type sodium ion battery positive electrode material.

2. The P2 type sodium ion battery positive electrode material according to claim 1, characterized in that: 0.65≤a≤0.68。 3. The P2 type sodium ion battery positive electrode material according to claim 1, characterized in that: In the P2 type sodium ion battery positive electrode material, the coating layer material accounts for 0.5% to 1% of the mass of the P2 type sodium ion battery positive electrode material.

4. The P2 type sodium ion battery positive electrode material according to claim 1, characterized in that: 1≤y / z≤2, 0.008≤y≤0.

15.

5. The P2 type sodium ion battery positive electrode material according to claim 1 or 2, characterized in that: The conductor coating material is a product of heat treatment of a mixture of Ti(HPO4)2 and MgHPO4 at a holding temperature of 650°C to 850°C, wherein the weight ratio of Ti(HPO4)2 to MgHPO4 is (2-8):

1.

6. The P2 type sodium ion battery positive electrode material according to claim 5, characterized in that: The conductor coating material is a product of heat treatment of a mixture of Ti(HPO4)2 and MgHPO4 at a holding temperature of 650°C to 850°C, wherein the weight ratio of Ti(HPO4)2 to MgHPO4 is (3-5):

1.

7. The method for preparing a positive electrode material for a P2 type sodium ion battery according to any one of claims 1 to 6, characterized in that: The method comprises the following steps: (1) The sodium source, nickel source, manganese source, gadolinium source and barium source are mixed evenly according to the stoichiometric ratio and then subjected to the first heat treatment to obtain the P2 matrix Na a Ni x Mn 2x G y Ba z O2; the first heat treatment holding temperature is 850 ℃ ~ 1050 ℃, the holding time is 8 ~ 16 hours, the heating rate is 3 ~ 5 ℃ / min, and the sintering atmosphere is air; (2) The Na obtained in step (1) a Ni x Mn 2x G y Ba z O2 material is crushed to a particle size of D00 ≥ 0.5 μm, 4.0 μm ≤ D50 ≤ 5.5 μm, and D100 ≤ 14 μm; (3) The material obtained in step (2) is uniformly mixed with Ti(HPO4)2 and MgHPO4 according to a mass ratio, and then subjected to a second heat treatment to obtain a high-voltage and high-rate P2 type sodium ion battery positive electrode material; the second heat treatment has a holding temperature of 650°C to 850°C, a holding time of 4 to 10 hours, a heating rate of 3 to 5°C / min, and an air sintering atmosphere; (4) The material obtained in step (3) is crushed to a particle size satisfying D00 ≥ 0.6 μm, 4.5 μm ≤ D50 ≤ 6.5 μm, and D100 ≤ 16 μm.

8. The method for preparing a positive electrode material for a P2 type sodium ion battery according to claim 7, characterized in that: The sodium source is one or more of sodium carbonate, sodium hydroxide and sodium oxalate; the nickel source is one or more of its oxides, oxalates or hydroxides; the manganese source and gadolinium source are their corresponding oxides; and the barium source is one or both of its carbonates and oxalates.

9. A sodium ion secondary battery, characterized in that: The sodium ion secondary battery comprises the P2 type sodium ion battery positive electrode material as claimed in any one of claims 1 to 6.

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