Layered oxide positive electrode material of P2-type sodium-ion battery and preparation method and application of layered oxide positive electrode material

Abstract

The invention discloses a layered oxide positive electrode material for a P2-type sodium-ion battery and a preparation method and application thereof.The preparation method of the layered oxide positive electrode material for the P2-type sodium-ion battery comprises the steps that a sodium source, a nickel source, a manganese source and other metal sources are mixed to be uniform, precursor powder is obtained, the other metal sources are oxides or salts of M, and the precursor powder is prepared in an air atmosphere; and calcining the precursor powder at 500-1100 DEG C for 6-36 hours, and cooling to room temperature to obtain the P2-type sodium-ion battery layered oxide positive electrode material. According to the invention, the bad phase change of the nickel-manganese-based layered oxide in the charging and discharging process of the battery is effectively inhibited through multi-element doping, so that the cycle life of the sodium-ion battery is prolonged; the sodium ion battery disclosed by the invention has relatively good cycle performance and rate capability at normal temperature and also has relatively good cycle performance in a relatively wide temperature range.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, specifically relating to a P2 type sodium-ion battery layered oxide cathode material, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries (LIBs) can be used in almost all portable electronic products, such as smartphones, laptops, tablets, and digital devices. With the development of electric vehicles and the increasing demand for renewable energy storage in grids, the demand for LIBs is constantly increasing. However, limited lithium resources are a key issue in the continuous production of batteries, restricting the sustainable development of LIBs. Sodium-ion batteries (SIBs), with their abundant crustal resources and low cost, are gaining increasing attention, especially in stationary energy storage and low-speed vehicles, and are expected to become the most promising next-generation energy storage device after lithium-ion batteries.

[0003] Improving the structural and cycle stability of sodium-ion batteries is a crucial issue currently facing the field. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing a layered oxide cathode material for P2 type sodium-ion batteries.

[0005] Another object of the present invention is to provide a P2 type sodium-ion battery layered oxide cathode material obtained by the above preparation method.

[0006] The objective of this invention is achieved through the following technical solution.

[0007] A layered oxide cathode material for P2 type sodium-ion batteries, with the general formula Na X Ni A Mn B M C O2; wherein M is one or more of Li, Ca, Cu, Zn, Mg, Al, Fe, B, Sn and Ti, 0.6≤X≤1, 0.15<A≤0.4, 0.4<B≤0.7, 0<C≤0.3, and A+B+C=1.

[0008] A method for preparing a layered oxide cathode material for a P2 type sodium-ion battery includes the following steps:

[0009] Step 1: Mix sodium source, nickel source, manganese source and other metal sources until homogeneous to obtain precursor powder. Other metal sources are oxides or salts of M. The ratio of sodium in sodium source, nickel in nickel source, manganese in manganese source and M in other metal sources by molar amount is 1.05X:A:B:C.

[0010] In step 1, sodium source, nickel source, manganese source and other metal sources are mixed and ball-milled until homogeneous to obtain precursor powder.

[0011] In the above technical solution, the ball milling time is 2 to 30 hours (preferably 4 to 8 hours), and the ball milling speed is 100 to 1000 rpm (preferably 200 to 500 rpm).

[0012] In step 1, the sodium source is sodium carbonate or sodium nitrate.

[0013] In step 1, the nickel source is nickel oxide.

[0014] In step 1, the manganese source is manganese dioxide.

[0015] In step 1, the preferred ratio of sodium in the sodium source, nickel in the nickel source, manganese in the manganese source, and M in other metal sources, based on the molar amounts, is 0.85:(0.2-0.3):(0.56-0.57):(0.15-0.22).

[0016] In step 1, the other metal sources are preferably lithium carbonate, magnesium oxide, zinc oxide, copper oxide, aluminum oxide, and tin dioxide.

[0017] In the above technical solution, the ratio of lithium in lithium carbonate, copper in copper oxide, magnesium in magnesium oxide, zinc in zinc oxide, aluminum in aluminum oxide, and tin in tin dioxide, by molar amounts, is (0.06~0.08):(0.01~0.02):(0.01~0.02):(0.01~0.02):(0.03~0.04):(0.03~0.04).

[0018] Step 2: In an air atmosphere, the precursor powder is calcined at 500-1100℃ for 6-36 hours and then cooled to room temperature to obtain the P2 type sodium-ion battery layered oxide cathode material.

[0019] In step 2, the heating rate to 500–1100°C is 1–10°C / min.

[0020] In step 2, calcination is preferably carried out at 500–1100°C for 8–12 hours.

[0021] A sodium-ion battery, comprising: a P2 type sodium-ion battery layered oxide cathode material.

[0022] In the above technical solution, at room temperature and 5C current density, the initial reversible capacity of the sodium-ion battery is 76.6 mAh / g, and the reversible capacity can still reach 70.1 mAh / g after 100 cycles, with a capacity retention rate of 91.5%.

[0023] In the above technical solution, at room temperature and 1C current density, the initial reversible capacity of the sodium-ion battery is up to 114.3 mAh / g, and the reversible capacity can still reach 104.5 mAh / g after 100 cycles, with a capacity retention rate of 91.4%.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. This invention effectively suppresses the undesirable phase transition of nickel-manganese base oxides during battery charging and discharging through multi-element doping, thereby extending the cycle life of sodium-ion batteries. The sodium-ion batteries of this invention have better cycle performance and rate performance at room temperature and also have good cycle performance in a wide temperature range (-45 to 55°C).

[0026] 2. This invention uses a high-temperature solid-state method to prepare layered oxide cathode materials for P2 type sodium-ion batteries. Compared with the co-precipitation method and the sol-gel method, the powder particles prepared by the high-temperature solid-state method are free from agglomeration and have good filling properties. Moreover, the process is simple, does not require complex equipment and high raw material costs, and is conducive to industrial production. Attached Figure Description

[0027] Figure 1 The images show X-ray powder diffraction patterns of the layered oxide cathode materials for P2 type sodium-ion batteries prepared in Examples 1-3.

[0028] Figure 2 SEM image of the layered oxide cathode material for P2 type sodium-ion batteries prepared in Example 1;

[0029] Figure 3 The first charge-discharge curves of the sodium-ion batteries prepared in Examples 4-6 are shown.

[0030] Figure 4 The graphs show the cycle performance of the sodium-ion batteries prepared in Examples 4-6 at 25°C and 1C current density.

[0031] Figure 5 The graph shows the cycle performance of the sodium-ion battery prepared in Example 4 at 25°C and 5C current density.

[0032] Figure 6 The graph shows the rate performance of the sodium-ion battery prepared in Example 4 at 25°C.

[0033] Figure 7 The graph shows the cycling performance of the sodium-ion battery prepared in Example 4 at -45°C and 0.2C current density.

[0034] Figure 8 The graph shows the rate performance of the sodium-ion battery prepared in Example 4 at -45°C.

[0035] Figure 9 The graph shows the cycling performance of the sodium-ion battery prepared in Example 4 at 55°C and 1.6C current density.

[0036] Figure 10 The graph shows the rate performance of the sodium-ion battery prepared in Example 4 at 55°C.

[0037] Figure 11 X-ray powder diffraction patterns of the layered oxide cathode materials for P2 type sodium-ion batteries prepared in Comparative Examples 1-5;

[0038] Figure 12 SEM image of the layered oxide cathode material for P2 type sodium-ion batteries prepared in Comparative Example 1;

[0039] Figure 13 The first charge-discharge curve of the sodium-ion battery prepared in Comparative Example 6 is shown.

[0040] Figure 14 The graph shows the cycling performance of the sodium-ion battery prepared in Comparative Example 6 at 25°C and 1C current density.

[0041] Figure 15 The graph shows the cycling performance of the sodium-ion battery prepared in Comparative Example 6 at -45℃ and 0.2C current density.

[0042] Figure 16 The graph shows the cycling performance of the sodium-ion battery prepared in Comparative Example 6 at 55°C and 1.6C current density.

[0043] Figure 17 The diagram shows the cycle performance of the sodium-ion battery prepared in Comparative Example 7 at 25°C and 1C current density.

[0044] Figure 18 The graph shows the cycle performance of the sodium-ion batteries prepared in Example 4 and Comparative Example 7 at 25°C and 1C current density.

[0045] Figure 19 The graph shows the cycle performance of the sodium-ion battery prepared in Comparative Example 7 at 25°C and 5C current density.

[0046] Figure 20 The graph shows the cycling performance of the sodium-ion battery prepared in Comparative Example 7 at -45℃ and 0.2C current density.

[0047] Figure 21 The graph shows the cycling performance of the sodium-ion battery prepared in Comparative Example 7 at 55°C and 1.6C current density.

[0048] Figure 22 The rate performance of the sodium-ion battery prepared in Comparative Example 7 at -45℃ is shown in the graph.

[0049] Figure 23 The rate performance of the sodium-ion battery prepared in Comparative Example 7 at 55°C is shown in the graph.

[0050] Figure 24 The cycling performance of the sodium-ion batteries prepared in Comparative Examples 8-10 at 25°C and 1C current density is shown in the graph.

[0051] Figure 25 The graph shows the cycle performance of the sodium-ion battery prepared in Comparative Example 8 at 25°C and 5C current density.

[0052] Figure 26 The diagram shows the cycle performance of the sodium-ion battery prepared in Comparative Example 9 at 25°C and 5C current density.

[0053] Figure 27 The graph shows the cycling performance of the sodium-ion battery prepared in Comparative Example 10 at 25°C and 5C current density. Detailed Implementation

[0054] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0055] The raw material information involved in the following examples is as follows:

[0056] Drug Name Model (Purity) Manufacturer (Anhydrous) Sodium carbonate Analytical Pure Shanghai Aladdin Biochemical Technology Co., Ltd. lithium carbonate Analytical Pure Shanghai Aladdin Biochemical Technology Co., Ltd. Nickel oxide Analytical Pure Shanghai McLean Biochemical Technology Co., Ltd. Manganese dioxide Analytical Pure Shanghai Aladdin Biochemical Technology Co., Ltd. Tin dioxide Analytical Pure Shanghai Aladdin Biochemical Technology Co., Ltd. magnesium oxide Analytical Pure Shanghai McLean Biochemical Technology Co., Ltd. copper oxide Analytical Pure Shanghai McLean Biochemical Technology Co., Ltd. Zinc oxide Analytical Pure Shanghai McLean Biochemical Technology Co., Ltd. Alumina Analytical Pure Shanghai McLean Biochemical Technology Co., Ltd. N-Methylpyrrolidone 99％ Tianjin Fuchen Company Conductive carbon black Chemically pure Tianjin Fuchen Company polyvinylidene fluoride Analytical Pure Shenzhen Kejing Zhida Technology Co., Ltd. electrolyte Battery level Duoduo Reagent

[0057] When mixing sodium, nickel, manganese and other metal sources, sodium source needs to be in excess to compensate for the sodium deficiency caused by sodium volatilization during calcination.

[0058] The X-ray diffractometer (Smart Lab 9kW, Rigaku Co., Beijing, China) uses a Cu target, a 9kW rotating anode target, a scintillation counter, and a one-dimensional detector. The test angle is 10°-80°, the operating voltage is 40kV, and the operating current is 150mA.

[0059] Scanning electron microscope: Quanta FEG 250.

[0060] The charge and discharge performance of sodium-ion batteries was tested using the CT 3002A test system manufactured by Wuhan Landian Electronics Co., Ltd.

[0061] In this invention, 0.1C = 15 mA / g.

[0062] Examples 1-3

[0063] A method for preparing a layered oxide cathode material for a P2 type sodium-ion battery includes the following steps:

[0064] Step 1: Mix sodium source, nickel source, manganese source and other metal sources, and ball mill in a stainless steel ball mill jar at 400 rpm for 6 hours until homogeneous (ball-to-material ratio is 10:1) to obtain precursor powder. Other metal sources are oxides or salts of M, where M is Li, Mg, Zn, Cu, Al and Sn. Other metal sources are lithium carbonate, magnesium oxide, zinc oxide, copper oxide, aluminum oxide and tin dioxide. Sodium source is sodium carbonate, nickel source is nickel oxide, and manganese source is manganese dioxide. By molar amount, the ratio of sodium in sodium source, nickel in nickel source, manganese in manganese source and M in other metal sources is Y. By molar amount, the ratio of lithium in lithium carbonate, copper in copper oxide, magnesium in magnesium oxide, zinc in zinc oxide, aluminum in aluminum oxide and tin in tin dioxide is Z.

[0065] Step 2: In an air atmosphere, the precursor powder is placed in a muffle furnace and calcined at 1050°C for 10 hours. After cooling to room temperature in the furnace, it is ground in a glove box to obtain the P2 type sodium-ion battery layered oxide cathode material. The heating rate to 1050°C is 10°C / min.

[0066] Y and Z are shown in Table 1.

[0067] Table 1

[0068]

[0069] XRD tests were performed on the P2-type sodium-ion battery layered oxide cathode materials prepared in Examples 1-3. The test results are as follows: Figure 1 As shown, the XRD diffraction peaks of the P2-type sodium-ion battery layered oxide cathode materials prepared in Examples 1-3 are consistent with the peak positions of the standard card "#27-0751" for the P2 phase, proving that the material is a pure P2 phase without other elemental impurities.

[0070] Figure 2 SEM image of the P2-type sodium-ion battery layered oxide cathode material obtained in Example 1, such as... Figure 2 As shown, the microstructure of the P2-type sodium-ion battery layered oxide cathode material obtained in Example 1 is micron-sized layered particles.

[0071] Comparative Example 1

[0072] A layered oxide cathode material for P2 type sodium-ion batteries (Na 0.85 Ni 0.33 Mn 0.67 The method for preparing O2 includes the following steps:

[0073] Step 1: Mix sodium source, nickel source and manganese source, and ball mill in a stainless steel ball mill jar at 400 rpm for 6 hours until homogeneous (ball-to-material ratio is 10:1) to obtain precursor powder. Sodium source is sodium carbonate, nickel source is nickel oxide, and manganese source is manganese dioxide. The ratio of sodium in sodium source, nickel in nickel source and manganese in manganese source by molar amount is 0.85:0.33:0.67.

[0074] Step 2 is the same as step 2 in Example 1.

[0075] Comparative Example 2

[0076] A layered oxide cathode material for P2 type sodium-ion batteries (Na 0.85 Li 0.08 Mg 0.04 Al 0.04 Ni 0.22 Mn 0.62 The method for preparing O2 includes the following steps:

[0077] Step 1: Mix sodium source, nickel source, manganese source and other metal sources, and ball mill in a stainless steel ball mill jar at 400 rpm for 6 hours until homogeneous (ball-to-material ratio is 10:1) to obtain precursor powder. Other metal sources are oxides or salts of M, where M is Li, Mg and Al, and other metal sources are lithium carbonate, magnesium oxide and aluminum oxide. Sodium source is sodium carbonate, nickel source is nickel oxide, and manganese source is manganese dioxide. By molar amount, the ratio of sodium in sodium source, nickel in nickel source, manganese in manganese source and M in other metal sources is 0.85:0.22:0.62:0.16. By molar amount, the ratio of lithium in lithium carbonate, magnesium in magnesium oxide and aluminum in aluminum oxide is 0.08:0.04:0.04.

[0078] Step 2 is the same as step 2 in Example 1.

[0079] Comparative Example 3

[0080] A layered oxide cathode material for P2 type sodium-ion batteries (Na 0.85 Li 0.08 Mg 0.02 Zn 0.02 Ni 0.24 Al 0.04 Mn 0.56 Sn 0.04 The method for preparing O2 includes the following steps:

[0081] Step 1: Mix sodium source, nickel source, manganese source and other metal sources, and ball mill in a stainless steel ball mill jar at 400 rpm for 6 hours until homogeneous (ball-to-material ratio is 10:1) to obtain precursor powder. Other metal sources are oxides or salts of M, where M is Li, Mg, Zn, Al and Sn. Other metal sources are lithium carbonate, magnesium oxide, zinc oxide, aluminum oxide and tin dioxide. Sodium source is sodium carbonate, nickel source is nickel oxide, and manganese source is manganese dioxide. By molar amount, the ratio of sodium in sodium source, nickel in nickel source, manganese in manganese source and M in other metal sources is 0.85:0.24:0.56:0.2. By molar amount, the ratio of lithium in lithium carbonate, magnesium in magnesium oxide, zinc in zinc oxide, aluminum in aluminum oxide and tin in tin dioxide is 0.08:0.02:0.02:0.04:0.04.

[0082] Step 2 is the same as step 2 in Example 1.

[0083] Comparative Example 4

[0084] A layered oxide cathode material for P2 type sodium-ion batteries (Na 0.85 Li 0.08 Mg 0.02 Cu 0.02 Ni 0.24 Al 0.04 Mn 0.56 Sn 0.04 The method for preparing O2 includes the following steps:

[0085] Step 1: Mix sodium source, nickel source, manganese source and other metal sources, and ball mill in a stainless steel ball mill jar at 400 rpm for 6 hours until homogeneous (ball-to-material ratio is 10:1) to obtain precursor powder. Other metal sources are oxides or salts of M, where M is Li, Mg, Cu, Al and Sn. Other metal sources are lithium carbonate, magnesium oxide, copper oxide, aluminum oxide and tin dioxide. Sodium source is sodium carbonate, nickel source is nickel oxide, and manganese source is manganese dioxide. By molar amount, the ratio of sodium in sodium source, nickel in nickel source, manganese in manganese source and M in other metal sources is 0.85:0.24:0.56:0.2. By molar amount, the ratio of lithium in lithium carbonate, copper in copper oxide, magnesium in magnesium oxide, aluminum in aluminum oxide and tin in tin dioxide is 0.08:0.02:0.02:0.04:0.04.

[0086] Step 2 is the same as step 2 in Example 1.

[0087] Comparative Example 5

[0088] A layered oxide cathode material for P2 type sodium-ion batteries (Na 0.85 Li 0.08 Mg 0.02 Zn 0.02 Cu0.02 Ni 0.22 Al 0.04 Mn 0.6 The method for preparing O2 includes the following steps:

[0089] Step 1: Mix sodium source, nickel source, manganese source and other metal sources, and ball mill in a stainless steel ball mill jar at 400 rpm for 6 hours until homogeneous (ball-to-material ratio is 10:1) to obtain precursor powder. Other metal sources are oxides or salts of M, where M is Li, Mg, Zn, Cu and Al, and other metal sources are lithium carbonate, magnesium oxide, zinc oxide, copper oxide and aluminum oxide. Sodium source is sodium carbonate, nickel source is nickel oxide, and manganese source is manganese dioxide. By molar amount, the ratio of sodium in sodium source, nickel in nickel source, manganese in manganese source and M in other metal sources is 0.85:0.22:0.60:0.18. By molar amount, the ratio of lithium in lithium carbonate, copper in copper oxide, magnesium in magnesium oxide, zinc in zinc oxide and aluminum in aluminum oxide is 0.08:0.02:0.02:0.02:0.04.

[0090] Step 2 is the same as step 2 in Example 1.

[0091] XRD tests were performed on the P2-type sodium-ion battery layered oxide cathode materials prepared in Comparative Examples 1-5. The test results are as follows: Figure 11 As shown, it can be seen that the P2-type sodium-ion battery layered oxide cathode materials prepared in Comparative Examples 1 to 5 are pure P2 phases.

[0092] Figure 12 SEM images of the P2-type sodium-ion battery layered oxide cathode material prepared in Comparative Example 1 are shown. Figure 12 As shown, the layered oxide cathode material for P2 type sodium-ion batteries prepared in Comparative Example 1 exhibits a distinct sheet-like morphology.

[0093] Examples 4-6 and Comparative Examples 6-10

[0094] A sodium-ion battery includes: a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode is a 12 mm diameter metallic sodium sheet, the separator is a 19 mm diameter glass fiber (Whitman, GF / A), and the electrolyte includes: sodium perchlorate (NaClO4), fluoroethylene carbonate (FEC), and propylene carbonate (PC). The concentration of sodium perchlorate in the electrolyte is 1.0 mol / L, and the concentration of fluoroethylene carbonate (FEC) in the electrolyte is 5 wt%. In a glove box, the positive electrode, separator, electrolyte, and negative electrode are assembled in that order. The method for obtaining the positive electrode includes: mixing the positive electrode material, conductive carbon black (Super P), polyvinylidene fluoride (PVDF), and N-methylpyrrolidone until homogeneous. The mass ratio of the positive electrode material, conductive carbon black (Super P), polyvinylidene fluoride (PVDF), and N-methylpyrrolidone is 80:10:10:0.5, where mass parts are in mg and volume parts are in ml. This yields a positive electrode slurry. The positive electrode slurry is coated onto a current collector (aluminum foil) and dried in a drying oven at 100°C for 12 hours, resulting in a 200 μm thick coating on the current collector. This coating is then cut into electrodes with a diameter of 10 mm to serve as the positive electrode. The positive electrode material is one of the layered oxide positive electrode materials for P2-type sodium-ion batteries prepared in Examples 1-3 and Comparative Examples 1-5 (as shown in Table 2).

[0095] Table 2

[0096] Sodium-ion batteries Positive electrode material used in the preparation of positive electrode sheets Example 4 Example 1 Example 5 Example 2 Example 6 Example 3 Comparative Example 6 Comparative Example 1 Comparative Example 7 Comparative Example 2 Comparative Example 8 Comparative Example 3 Comparative Example 9 Comparative Example 4 Comparative Example 10 Comparative Example 5

[0097] The sodium-ion batteries prepared in Examples 4-6 were tested at room temperature (25°C) and a current density of 15 mAg. -1 The first charge-discharge test was conducted under the following conditions, and the test results are as follows: Figure 3 As shown. By Figure 3 It can be seen that the initial discharge capacity of the sodium-ion battery prepared in Example 4 can reach 121.6 mAh / g, the initial discharge capacity of the sodium-ion battery prepared in Example 5 can reach 108.3 mAh / g, and the initial discharge capacity of the sodium-ion battery prepared in Example 6 can reach 112.0 mAh / g.

[0098] The sodium-ion batteries prepared in Examples 4-6 were subjected to cycle tests at room temperature (25°C) and a current density of 1C (150 mA / g). The test results are as follows: Figure 4 As shown. By Figure 4It can be seen that the initial reversible capacity of the sodium-ion battery prepared in Example 4 is 114.3 mAh / g, and the reversible capacity can still reach 104.5 mAh / g after 100 cycles, with a capacity retention rate of 91.4%; the initial reversible capacity of Example 5 is 99.1 mAh / g, and the reversible capacity can reach 87.0 mAh / g after 100 cycles; the initial reversible capacity of Example 6 is 102.7 mAh / g, and the reversible capacity can reach 89.5 mAh / g after 100 cycles.

[0099] The sodium-ion battery prepared in Example 4 was subjected to cycle testing at room temperature (25°C) and a current density of 5C (750 mA / g). The test results are as follows: Figure 5 As shown. By Figure 5 It can be seen that the initial reversible capacity of the sodium-ion battery prepared in Example 4 is 76.6 mAh / g, and the reversible capacity can still reach 70.1 mAh / g after 100 cycles, with a capacity retention rate of 91.5%.

[0100] The sodium-ion battery prepared in Example 4 was subjected to rate testing at 25°C and current densities of 0.1C, 0.2C, 0.4C, 0.8C, 1.6C, and 3.2C, respectively, with 5 cycles at each current density. The test results are as follows: Figure 6 As shown. By Figure 6 It can be seen that, at current densities of 0.1C, 0.2C, 0.4C, 0.8C, 1.6C and 3.2C, the discharge specific capacity (average value) of the sodium-ion battery prepared in Example 4 is 121.6mAh / g, 113.1mAh / g, 107.6mAh / g, 102.1mAh / g, 90.1mAh / g and 87.8mAh / g, respectively.

[0101] The sodium-ion battery prepared in Example 4 was subjected to cycle testing at -45°C and a current density of 0.2C (30 mA / g). The test results are as follows: Figure 7 As shown. By Figure 7 It can be seen that the initial reversible capacity of the sodium-ion battery prepared in Example 4 is 92.2 mAh / g, and the reversible capacity can still reach 84.1 mAh / g after 100 cycles, with a capacity retention rate of 91.2%.

[0102] The sodium-ion battery prepared in Example 4 was subjected to rate testing at -45°C and current densities of 0.1C, 0.2C, 0.4C, 0.8C, and 1.6C, respectively, with 5 cycles at each current density. The test results are as follows: Figure 8 As shown. By Figure 8It can be seen that, at current densities of 0.1C, 0.2C, 0.4C, 0.8C and 1.6C, the discharge specific capacity (average value) of the sodium-ion battery prepared in Example 4 is 100.4 mAh / g, 93.1 mAh / g, 90.2 mAh / g, 75.2 mAh / g and 50.1 mAh / g, respectively.

[0103] The sodium-ion battery prepared in Example 4 was subjected to cycle testing at 55°C and a current density of 1.6C (240 mA / g). The test results are as follows: Figure 9 As shown. By Figure 9 It can be seen that the initial reversible capacity of the sodium-ion battery prepared in Example 4 is 113.1 mAh / g, and the reversible capacity can still reach 83.2 mAh / g after 100 cycles, with a capacity retention rate of 73.6%.

[0104] The sodium-ion battery prepared in Example 4 was subjected to rate testing at 55°C and current densities of 0.1C, 0.2C, 0.4C, 0.8C, 1.6C, and 3.2C, respectively, with 5 cycles at each current density. The test results are as follows: Figure 10 As shown. By Figure 10 It can be seen that, at current densities of 0.1C, 0.2C, 0.4C, 0.8C, 1.6C and 3.2C, the discharge specific capacities of the sodium-ion batteries prepared in Example 4 are 140.5 mAh / g, 139.1 mAh / g, 134.4 mAh / g, 124.2 mAh / g, 108.9 mAh / g and 87.7 mAh / g, respectively.

[0105] The sodium-ion battery prepared in Comparative Example 6 was tested at room temperature (25°C) and a current density of 15 mAg. -1 The first charge-discharge test was conducted under the following conditions, and the test results are as follows: Figure 13 As shown. By Figure 13 It can be seen that the initial discharge capacity of Comparative Example 6 can reach 138.1 mAh / g.

[0106] The sodium-ion battery prepared in Comparative Example 6 was subjected to cycle testing at room temperature (25℃) and a current density of 1C (150mA / g). The test results are as follows. Figure 14 As shown. By Figure 14 It can be seen that the initial reversible capacity of the sodium-ion battery prepared in Comparative Example 6 is 100.67 mAh / g, and the reversible capacity can still reach 64.9 mAh / g after 100 cycles, with a capacity retention rate of 64.5%.

[0107] The sodium-ion battery prepared in Comparative Example 6 was subjected to cycle testing at -45℃ and a current density of 0.2C (30 mA / g). The test results are as follows: Figure 15 As shown. By Figure 15It can be seen that the initial reversible capacity of the sodium-ion battery prepared in Comparative Example 6 is 74.7 mAh / g, the reversible capacity after 100 cycles is 65.5 mAh / g, and the capacity retention rate is 87.7%.

[0108] The sodium-ion battery prepared in Comparative Example 6 was subjected to cycle testing at 55°C and a current density of 1.6C (240 mA / g). The test results are as follows. Figure 16 As shown. By Figure 16 It can be seen that the sodium-ion battery prepared in Comparative Example 6 has a low reversible capacity, with an initial reversible capacity of 78.5 mAh / g and a reversible capacity of 73.4 mAh / g after 100 cycles, and a capacity retention rate of 93.5%.

[0109] The sodium-ion battery prepared in Comparative Example 7 was subjected to cycle testing at room temperature (25℃) and a current density of 1C (150mA / g). The test results are as follows. Figure 17 As shown. By Figure 17 It can be seen that the initial reversible capacity of the sodium-ion battery prepared in Comparative Example 7 is 99.0 mAh / g, and the reversible capacity can reach 89.8 mAh / g after 100 cycles.

[0110] The sodium-ion batteries prepared in Example 4 and Comparative Example 7 were subjected to cycle tests at room temperature (25°C) and a current density of 1C (150 mA / g), respectively. The test results are as follows: Figure 18 As shown. By Figure 18 It can be seen that the initial reversible capacity of the sodium-ion battery prepared in Example 4 is 114.2 mAh / g, and the reversible capacity can still reach 67.5 mAh / g after 300 cycles, with a capacity retention rate of 59.1%; the initial reversible capacity of the sodium-ion battery prepared in Comparative Example 7 is 99.0 mAh / g, and the reversible capacity is 44.4 mAh / g after 300 cycles, with a capacity retention rate of 44.8%.

[0111] The sodium-ion battery prepared in Comparative Example 7 was subjected to cycle testing at room temperature (25°C) and a current density of 5C (750 mA / g). The test results are as follows. Figure 19 As shown. By Figure 19 It can be seen that the initial reversible capacity of the sodium-ion battery prepared in Comparative Example 7 is 70.9 mAh / g, the reversible capacity is 58.8 mAh / g after 100 cycles, and the capacity retention rate is 82.9%.

[0112] The sodium-ion battery prepared in Comparative Example 7 was subjected to cycle testing at -45℃ and a current density of 0.2C (30 mA / g). The test results are as follows: Figure 20 As shown. By Figure 20It can be seen that the initial reversible capacity of the sodium-ion battery prepared in Comparative Example 7 is 86.3 mAh / g, the reversible capacity is 79.0 mAh / g after 100 cycles, and the capacity retention rate is 91.5%.

[0113] The sodium-ion battery prepared in Comparative Example 7 was subjected to cycle testing at 55°C and a current density of 1.6C (240 mA / g). The test results are as follows. Figure 21 As shown. By Figure 21 It can be seen that the initial reversible capacity of the sodium-ion battery prepared in Comparative Example 7 is 112.3 mAh / g, and the reversible capacity after 100 cycles is 87.2 mAh / g, with a capacity retention rate of 77.6%. The sodium-ion battery prepared in Comparative Example 7 exhibits similar cycle performance to that of Example 4 at both high and low temperatures, but the cycle stability of Comparative Example 7 is poor at room temperature.

[0114] The sodium-ion battery prepared in Comparative Example 7 was subjected to rate testing at -45°C and current densities of 0.1C, 0.2C, 0.4C, 0.8C, and 1.6C, respectively, with 5 cycles at each current density. The test results are as follows. Figure 22 As shown. By Figure 22 It can be seen that the average discharge specific capacity of the sodium-ion battery prepared in Comparative Example 7 at current densities of 0.1C, 0.2C, 0.4C, 0.8C, and 1.6C are 89.2 mAh / g, 87.1 mAh / g, 81.3 mAh / g, 70.6 mAh / g, and 49.1 mAh / g, respectively. Compared with Example 4, the sodium-ion battery prepared in Comparative Example 7 exhibits poorer low-temperature rate performance.

[0115] The sodium-ion battery prepared in Comparative Example 7 was subjected to rate testing at 55°C and current densities of 0.1C, 0.2C, 0.4C, 0.8C, 1.6C, and 3.2C, respectively, with 5 cycles at each current density. The test results are as follows. Figure 23 As shown. By Figure 23 It can be seen that, at current densities of 0.1C, 0.2C, 0.4C, 0.8C, 1.6C, and 3.2C, the discharge specific capacities of the sodium-ion battery prepared in Comparative Example 7 are 120.5 mAh / g, 118.2 mAh / g, 117.3 mAh / g, 108.3 mAh / g, 98.1 mAh / g, and 85.2 mAh / g, respectively. Compared with Example 4, the sodium-ion battery prepared in Comparative Example 7 exhibits poor high-temperature rate performance.

[0116] The sodium-ion battery was subjected to cycle testing at room temperature (25°C) and a current density of 1C (150 mA / g). This sodium-ion battery was one of the sodium-ion batteries prepared in Comparative Examples 8-10. The test results are as follows: Figure 24 As shown. By Figure 24It can be seen that the initial reversible capacity of the sodium-ion battery prepared in Comparative Example 8 is 96.8 mAh / g, and the reversible capacity can reach 82.6 mAh / g after 100 cycles. The initial reversible capacity of the sodium-ion battery prepared in Comparative Example 9 is 89.3 mAh / g, and the reversible capacity can reach 76.1 mAh / g after 100 cycles. The initial reversible capacity of the sodium-ion battery prepared in Comparative Example 10 is 102.3 mAh / g, and the reversible capacity can reach 78.6 mAh / g after 100 cycles.

[0117] The sodium-ion battery prepared in Comparative Example 8 was subjected to cycle testing at room temperature (25°C) and a current density of 5C (750 mA / g). The test results are as follows: Figure 25 As shown. By Figure 25 It can be seen that the initial reversible capacity of Comparative Example 8 is 71.2 mAh / g, and the reversible capacity can reach 63.6 mAh / g after 100 cycles, with a capacity retention rate of 88.8%.

[0118] The sodium-ion battery prepared in Comparative Example 9 was subjected to cycle testing at room temperature (25℃) and a current density of 5C (750mA / g). The test results are as follows: Figure 26 As shown. By Figure 26 It can be seen that the initial reversible capacity of Comparative Example 9 is 68.0 mAh / g, and the reversible capacity can reach 57.5 mAh / g after 100 cycles, with a capacity retention rate of 84.5%.

[0119] The sodium-ion battery prepared in Comparative Example 10 was subjected to cycle testing at room temperature (25°C) and a current density of 5C (750 mA / g). The test results are as follows: Figure 27 As shown. By Figure 27 It can be seen that the initial reversible capacity of Comparative Example 10 is 84.2 mAh / g, and the reversible capacity can reach 67.6 mAh / g after 100 cycles, with a capacity retention rate of 80.0%.

[0120] The performance comparison of Examples 4 and Comparative Examples 6-10 at lower current densities (150 mA / g) and higher current densities (750 mA / g) shows that the materials prepared without any one of Li, Mg, Zn, Cu, Al, and Sn exhibit significantly lower performance than those of Example 4. This demonstrates that Li, Mg, Zn, Cu, Al, and Sn play indispensable roles in co-doping. The sodium-ion battery prepared in Example 4 exhibits good performance at room temperature, low temperature, high temperature, and high current density.

[0121] Sodium-ion battery layered metal oxide cathode materials can be mainly classified into P2, P3, O2, and O3 types based on their structure. In the O-type (O2 and O3) structure, sodium ions are located at octahedral sites; while in the P-type (P2 and P3) structure, sodium ions are located at prismatic sites. The difference in crystal structure between different types of materials leads to fundamental differences in their electrochemical performance. Taking P2 and P3 materials as examples, P2 materials have a hexagonal structure with two alternating layers of alkali metal ions and transition metal layers, while P3 materials adopt a three-layer stacking mode. This difference in the number of stacked layers directly affects the size of the sodium ion diffusion channel, thereby changing the ion migration rate and kinetic performance. Therefore, it is difficult to directly compare P2 and P3 materials.

[0122] The present invention has been described above by way of example. It should be noted that any simple modifications, alterations or other equivalent substitutions that can be made by those skilled in the art without creative effort without departing from the core of the present invention fall within the protection scope of the present invention.

Claims

1. A layered oxide cathode material for P2 type sodium-ion batteries, characterized in that, Its general formula is Na X Ni A Mn B M C O2; wherein M is one or more of Li, Ca, Cu, Zn, Mg, Al, Fe, B, Sn and Ti, 0.6≤X≤1, 0.15<A≤0.4, 0.4<B≤0.7, 0<C≤0.3, and A+B+C=1.

2. A method for preparing a layered oxide cathode material for a P2 type sodium-ion battery, characterized in that, Includes the following steps: Step 1: Mix sodium source, nickel source, manganese source and other metal sources until homogeneous to obtain precursor powder. Other metal sources are oxides or salts of M. The ratio of sodium in sodium source, nickel in nickel source, manganese in manganese source and M in other metal sources by molar amount is 1.05X:A:B:C. Step 2: In an air atmosphere, the precursor powder is calcined at 500-1100℃ for 6-36 hours and then cooled to room temperature to obtain the P2 type sodium-ion battery layered oxide cathode material.

3. The preparation method according to claim 2, characterized in that, In step 1, the ratio of sodium in the sodium source, nickel in the nickel source, manganese in the manganese source, and M in other metal sources, by molar amount, is 0.85:(0.2-0.3):(0.56-0.57):(0.15-0.22).

4. The preparation method according to claim 2, characterized in that, In step 1, the other metal sources are lithium carbonate, magnesium oxide, zinc oxide, copper oxide, aluminum oxide, and tin dioxide.

5. The preparation method according to claim 4, characterized in that, Based on the molar amounts of substances, the ratio of lithium in lithium carbonate, copper in copper oxide, magnesium in magnesium oxide, zinc in zinc oxide, aluminum in aluminum oxide, and tin in tin dioxide is (0.06~0.08):(0.01~0.02):(0.01~0.02):(0.01~0.02):(0.03~0.04):(0.03~0.04).

6. The preparation method according to claim 2, characterized in that, In step 1, sodium source, nickel source, manganese source and other metal sources are mixed and ball-milled until homogeneous to obtain precursor powder.

7. The preparation method according to claim 2, characterized in that, The sodium source is sodium carbonate or sodium nitrate, the nickel source is nickel oxide, and the manganese source is manganese dioxide.

8. A sodium-ion battery, characterized in that, include: The layered oxide cathode material for P2 type sodium-ion batteries as described in claim 1.

9. The sodium-ion battery according to claim 8, characterized in that, At room temperature and a 5C current density, the sodium-ion battery has an initial reversible capacity of 76.6 mAh / g, and after 100 cycles, the reversible capacity still reaches 70.1 mAh / g, with a capacity retention rate of 91.5%.

10. The sodium-ion battery according to claim 8, characterized in that, At room temperature and a current density of 1C, the sodium-ion battery has an initial reversible capacity of up to 114.3 mAh / g, and after 100 cycles, the reversible capacity can still reach 104.5 mAh / g, with a capacity retention rate of 91.4%.

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