P2 / O3 composite phase sodium ion battery positive electrode material as well as preparation method and application thereof

Abstract

The invention discloses a P2 / O3 composite phase sodium ion battery positive electrode material and a preparation method and application thereof, the chemical formula of the P2 / O3 composite phase sodium ion battery positive electrode material is NaxNiyMnzO2, wherein 0.67 lt; xlt; 1, 0.33 lt; yt; Yt; 0.5, 0.5 lt; zlt, zlt; 0.67); the preparation method comprises the following steps: uniformly mixing a nickel-manganese binary precursor and a sodium salt to obtain a mixed material; in an oxygen atmosphere, the mixed material is sintered for the first time, then is heated to be sintered for the second time, and is cooled along with a furnace to obtain a blocky material; and mechanically crushing, dissociating and sieving the blocky material to obtain the P2 / O3 composite phase sodium ion battery positive electrode material. According to the invention, the P2 phase and the O3 phase are fused in a microscale, the large-particle-size submicron P2 / O3 composite phase positive electrode material is prepared, and a battery assembled based on the P2 / O3 composite phase positive electrode material is high in first coulombic efficiency, high in specific discharge capacity and good in cycling stability.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion battery materials, and in particular to a P2 / O3 composite phase sodium ion battery positive electrode material, a preparation method thereof, and applications thereof. Background Art

[0002] With the rapid growth of the new energy industry, sodium-ion batteries (Na-ion batteries) have attracted widespread attention due to their numerous advantages, including low raw material costs, high energy density, long cycle life, safety, and environmental friendliness. The cathode materials for Na-ion batteries have been a major bottleneck restricting their development, and further increasing capacity and reducing costs have become urgent issues. Currently, Na-ion layered cathode materials still face many key challenges, such as the Jahn-Teller effect, transition metal ion migration and dissolution, ordered / disordered cation arrangement, air instability, and frequent structural phase transitions, which severely restrict the battery's cycle life.

[0003] Layered oxide cathode materials have the advantages of low cost and high working voltage, and have become an important research direction for the next generation of sodium ion battery cathode materials. However, the performance of single-phase materials themselves has limitations. The P2 phase has the advantages of high rate / cycle performance, but the specific capacity is low (≤100mAh g -1 ); O3 phase has high specific capacity (>120mAh g -1 ) advantages, but poor air stability, drastic phase change, and low cycle retention rate (<80%).

[0004] Due to the limitations of the performance of single-phase materials themselves, composite phase positive electrode materials have begun to develop in order to obtain positive electrode materials with better performance. The use of composite phase positive electrode materials can combine the advantages of each phase to obtain a positive electrode with better overall performance. In addition, the synergistic effect between multiple phases can also inhibit the adverse phase changes that occur during the charging and discharging process to a certain extent, thereby improving the structural stability of the material. P2 / O3 composite phase sodium ion battery positive electrode material is a new type of positive electrode material that combines two different layered oxide structures (P2 type and O3 type), which aims to synergistically improve the performance of sodium ion batteries through structural composites.

[0005] Therefore, the development of a P2 / O3 composite phase sodium ion battery positive electrode material with high specific capacity and excellent cycle stability is of great significance to the development of sodium ion batteries. Summary of the Invention

[0006] In view of the above-mentioned shortcomings, the present invention provides a P2 / O3 composite phase sodium ion battery positive electrode material, its preparation method, and application. This invention addresses the problems of low P2 phase capacity, poor air stability of the O3 phase, drastic phase transition, and cycle retention in layered positive electrode materials for sodium ion batteries. The invention provides a one-step sintering method for preparing a P2 / O3 composite phase sodium ion battery positive electrode material. By precisely controlling the stoichiometric ratio, sintering atmosphere, and temperature program, the P2 phase and O3 phase are blended at the microscale to prepare a large-particle submicron P2 / O3 composite phase positive electrode material. Batteries assembled with the P2 / O3 composite phase positive electrode material prepared by the present invention have high first coulombic efficiency, high discharge specific capacity, and good cycle stability.

[0007] In order to achieve the above object, the present invention provides a method for preparing a positive electrode material of a P2 / O3 composite phase sodium ion battery, wherein the chemical formula of the positive electrode material of the P2 / O3 composite phase sodium ion battery is Na x Ni y Mn z O2, of which 0.67 <x<1,0.33<y<0.5,0.5<z<0.67;

[0008] The preparation method comprises the following steps:

[0009] S1. Mixing a nickel-manganese binary precursor and a sodium salt to obtain a mixed material;

[0010] S2. In an oxygen atmosphere, the mixed material is subjected to a first sintering, and then the temperature is raised to perform a second sintering, and after cooling in the furnace, a block material is obtained;

[0011] S3. Mechanically crushing and disintegrating the bulk material, and sieving it to obtain a P2 / O3 composite phase sodium ion battery positive electrode material.

[0012] According to one aspect of the present invention, the total proportion of P2 phase and O3 phase in the P2 / O3 composite phase sodium ion battery positive electrode material is 100%, and the molar ratio of P2 phase to O3 phase is 4:1, 2:1, 1:1, 1:2 or 1:4.

[0013] According to one aspect of the present invention, the space group of the P2 phase is P63 / mmc, and the space group of the O3 phase is R3m.

[0014] According to one aspect of the present invention, in step S1, the amount of Ni in the nickel-manganese binary precursor is 33-50% of the total amount of Ni and Mn; the amount of Mn in the nickel-manganese binary precursor is 50-67% of the total amount of Ni and Mn.

[0015] According to one aspect of the present invention, in step S1, the nickel-manganese binary precursor includes at least one of nickel-manganese oxide, nickel-manganese carbonate, nickel-manganese sulfate, and nickel-manganese hydroxide; and the sodium salt includes at least one of sodium oxide, sodium peroxide, sodium hydroxide, sodium carbonate, and sodium bicarbonate.

[0016] According to one aspect of the present invention, in step S1, the mixing process is: placing the nickel-manganese binary precursor and the sodium salt in a stirring device, stirring at 10,000-20,000 rpm for 1-3 minutes at 5-30°C, cooling for 5-30 minutes, and repeating 1-5 times.

[0017] According to one aspect of the present invention, in step S2, the oxygen intake flow rate is 0.3-6m 3 h -1 ; The oxygen content of the first sintering is ≥98%.

[0018] According to one aspect of the present invention, in step S2, the heating rate of the first sintering is 1-5°C min -1 , the temperature is 200-400℃, the time is 1-4h; the cooling rate is 1-10℃min -1 The heating rate of the second sintering is 1-5℃min -1 , temperature is 800-950℃, time is 8-12h.

[0019] Based on the same inventive concept, the present invention also provides a P2 / O3 composite phase sodium ion battery positive electrode material prepared by the above preparation method.

[0020] Based on the same inventive concept, the present invention also provides the application of the above-mentioned P2 / O3 composite phase sodium ion battery positive electrode material in sodium ion batteries.

[0021] Preparation mechanism of the present invention:

[0022] A one-step controlled sintering process is used to prepare a P2 / O3 composite phase cathode material with submicron particle size, high capacity and high cycle performance. The one-step controlled sintering process refers to fully mixing the precursor with the sodium salt, and directly synthesizing the P2 / O3 composite phase cathode material in one step by performing two temperature program controls under a specific atmosphere, thereby achieving atomic-level dispersion of transition metal ions (Ni / Mn), eliminating local component segregation, and dispersing secondary particles to obtain a large-particle-size P2 / O3 composite phase cathode material.

[0023] Beneficial effects of the present invention:

[0024] (1) The present invention uses a simple high-temperature solid-phase method combined with a one-step controllable sintering process to suppress abnormal grain growth and obtain submicron primary particles, which greatly reduces the difficulty of synthesizing and preparing the P2 / O3 composite phase. Through dynamic compensation of sodium ions in the composite phase, the order of the transition metal layer is improved and the Jahn-Teller distortion is weakened.

[0025] (2) The ratio of the P2 / O3 composite phase positive electrode material prepared by the present invention is controllable, and a composite phase positive electrode material with an accurate ratio can be synthesized by a specific preparation method;

[0026] (3) The present invention can select a specific ratio of P2 / O3 composite phase according to the required electrochemical performance, and the resulting composite phase has good electrochemical performance;

[0027] (4) The preparation process of the present invention is simple and can be promoted, has little environmental pollution, excellent economic benefits, and has great commercial value. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 are SEM images of the positive electrode materials prepared in Examples 1-5 of the present invention and Comparative Example 1; wherein, ab are SEM images of the P2 / O3 composite phase positive electrode material prepared in Example 1 at different magnifications; cd are SEM images of the P2 / O3 composite phase positive electrode material prepared in Example 2 at different magnifications; ef are SEM images of the P2 / O3 composite phase positive electrode material prepared in Example 3 at different magnifications; gh are SEM images of the P2 / O3 composite phase positive electrode material prepared in Example 4 at different magnifications; ij are SEM images of the P2 / O3 composite phase positive electrode material prepared in Example 5 at different magnifications; kl are SEM images of the positive electrode material prepared in Comparative Example 1 at different magnifications;

[0029] Figure 2 XRD patterns of the positive electrode materials prepared in Examples 1-5 and Comparative Example 1 of the present invention;

[0030] Figure 3 This is a comparison chart of the first charge-discharge curves of the positive electrode materials prepared in Example 2 of the present invention and Comparative Example 1 tested at 25°C;

[0031] Figure 4 This is a comparison chart of the 1C cycle performance of the positive electrode materials prepared in Example 2 of the present invention and Comparative Example 1 tested at 25°C;

[0032] Figure 5 This is a comparison chart of the rate performance of the positive electrode materials prepared in Example 2 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0033] In order to make the present application more easily understood, the present application is further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present application and are not used to limit the scope of the present application. Obviously, the described examples are only a part of the examples of the present application, but not all the examples. Based on the examples in the present application, all other examples obtained by those skilled in the art without creative efforts fall within the scope of protection of the present application. Unless otherwise defined, the professional terms used below are consistent with the meanings understood by those skilled in the art; unless otherwise specified, the raw materials and reagents involved in the present application can be purchased from the market or prepared by known methods.

[0034] It should be noted that the present application is not limited to the examples Figure 2-5 In the present application, "Example 1, Example 2, Example 3, Example 4, Example 5 and Comparative Example 1" refer to "Example 1, Example 2, Example 3, Example 4, Example 5 and Comparative Example 1" in the specification, respectively.

[0035] In order to solve the problems of low specific capacity of P2 phase and poor air stability, severe phase transition and cycle retention rate of O3 phase of a layered positive electrode material of a sodium ion battery, the present application provides a preparation method of a P2 / O3 composite phase sodium ion battery positive electrode material, and the chemical formula of the P2 / O3 composite phase sodium ion battery positive electrode material is Na x Ni y Mn z O2, wherein 0.67 < x < 1, 0.33 < y < 0.5, and 0.5 < z < 0.67.

[0036] The preparation method comprises the following steps:

[0037] S1, uniformly mixing a nickel-manganese binary precursor and a sodium salt to obtain a mixture;

[0038] S2, performing first sintering on the mixture in an oxygen atmosphere, then performing second sintering by increasing the temperature, and obtaining a blocky material after furnace cooling;

[0039] S3, mechanically crushing and dissociating the blocky material, and sieving to obtain the P2 / O3 composite phase sodium ion battery positive electrode material.

[0040] It should be noted that the P2 / O3 composite phase sodium ion battery positive electrode material has P2 phase and O3 phase structures, which are uniformly distributed and are compounded at the micron scale.

[0041] In some specific embodiments, the total proportion of the P2 phase and the O3 phase in the P2 / O3 composite phase sodium ion battery positive electrode material is 100%, and the molar ratio of the P2 phase to the O3 phase is 4:1, 2:1, 1:1, 1:2 or 1:4.

[0042] In some specific embodiments, the molar ratio of Na / TM is 0.70-0.98; wherein TM is the total transition metal (Ni, Mn) amount.

[0043] In some specific embodiments, the space group of the P2 phase is P63 / mmc, and the space group of the O3 phase is R3m.

[0044] In some specific embodiments, in step S1, the amount of Ni in the nickel-manganese binary precursor is 33-50% of the total amount of Ni and Mn; the amount of Mn in the nickel-manganese binary precursor is 50-67% of the total amount of Ni and Mn.

[0045] In some specific embodiments, in step S1, the nickel-manganese binary precursor includes at least one of nickel-manganese oxide, nickel-manganese carbonate, nickel-manganese sulfate, and nickel-manganese hydroxide; and the sodium salt includes at least one of sodium oxide, sodium peroxide, sodium hydroxide, sodium carbonate, and sodium bicarbonate.

[0046] In some specific embodiments, in step S1, the mixing process is: placing the nickel-manganese binary precursor and the sodium salt in a stirring device, stirring at 10,000-20,000 rpm for 1-3 minutes at 5-30°C, cooling for 5-30 minutes, and repeating 1-5 times.

[0047] In some specific embodiments, in step S2, the oxygen intake flow rate is 0.3-6m 3 h -1 ; The oxygen content of the first sintering is ≥98%.

[0048] In some specific embodiments, in step S2, the heating rate of the first sintering is 1-5°C min -1 , the temperature is 200-400℃, the time is 1-4h; the cooling rate is 1-10℃min -1 The heating rate of the second sintering is 1-5℃min -1 , temperature is 800-950℃, time is 8-12h.

[0049] The present invention also provides a P2 / O3 composite phase sodium ion battery positive electrode material prepared by the above preparation method.

[0050] The present invention also provides the use of the above-mentioned P2 / O3 composite phase sodium ion battery positive electrode material in a sodium ion battery.

[0051] The following is further described with reference to specific embodiments and comparative examples.

[0052] Example 1

[0053] A method for preparing a P2 / O3 composite phase sodium ion battery positive electrode material comprises the following steps:

[0054] (1) Accurately weigh 4 mol Ni 0.33 Mn 0.67 (OH)2 precursor, 1 molNi 0.5 Mn 0.5 (OH)2 precursor, 1.932 mol Na2CO3 sodium salt, the precursor and sodium salt are mixed in a high-speed mixer at a stirring rate of 10000 r min -1 , the stirring time is 1 minute, the cooling time after stirring is 10 minutes, and this is repeated 3 times to obtain a mixed material; the molar ratio of Na / TM is 3.864 / 5=0.7728; TM is the total transition metal (Ni, Mn) content;

[0055] (2) Introduce pure oxygen atmosphere (≥98%) and control the air flow rate to 1.08m 3 h -1 , at 3℃min -1 The heating rate was raised to 200℃ and kept at this temperature for 2 hours for the first sintering. The heating rate was continued to rise to 900℃ and kept at this temperature for 12 hours for the second sintering. -1 Cool to room temperature to obtain a bulk material;

[0056] (3) The bulk material was crushed in a dry environment for 40 seconds and passed through a 200-mesh sieve to obtain large-particle Na with high capacity and high circulation. 0.736 Ni 0.364 Mn 0.636 O2-P2 / O3 composite phase positive electrode material.

[0057] Example 2

[0058] A method for preparing a P2 / O3 composite phase sodium ion battery positive electrode material comprises the following steps:

[0059] (1) Accurately weigh 4 mol Ni 0.33 Mn 0.67 (OH)2 precursor, 2 molNi 0.5 Mn 0.5 (OH)2 precursor, 2.457 mol Na2CO3 sodium salt, the precursor and sodium salt are mixed in a high-speed mixer at a stirring rate of 10000 r min -1 , the stirring time is 1 minute, the cooling time after stirring is 10 minutes, and this is repeated 3 times to obtain a mixed material; the molar ratio of Na / TM is 4.914 / 6=0.8190; TM is the total transition metal (Ni, Mn) content;

[0060] (2) Introduce pure oxygen atmosphere (≥98%) and control the air flow rate to 1.08m 3 h -1 , at 3℃min -1 The heating rate was raised to 200℃ and kept at this temperature for 2 hours for the first sintering. The heating rate was continued to rise to 900℃ and kept at this temperature for 12 hours for the second sintering. -1 Cool to room temperature to obtain a bulk material;

[0061] (3) The bulk material was crushed in a dry environment for 40 seconds and passed through a 200-mesh sieve to obtain large-particle Na with high capacity and high circulation. 0.779 Ni 0.386 Mn 0.614 O2-P2 / O3 composite phase positive electrode material.

[0062] Example 3

[0063] A method for preparing a P2 / O3 composite phase sodium ion battery positive electrode material comprises the following steps:

[0064] (1) Accurately weigh 2.5 mol Ni 0.33 Mn 0.67 (OH)2 precursor, 2.5 molNi 0.5 Mn 0.5 (OH)2 precursor, 2.192 mol Na2CO3 sodium salt, the precursor and sodium salt are mixed in a high-speed mixer at a stirring rate of 10000 r min -1 , the stirring time is 1 minute, the cooling time after stirring is 10 minutes, and this is repeated 3 times to obtain a mixed material; the molar ratio of Na / TM is 4.384 / 5=0.8768; TM is the total transition metal (Ni, Mn) content;

[0065] (2) Introduce pure oxygen atmosphere (≥98%) and control the air flow rate to 1.08m 3 h -1 , at 3℃min -1 The heating rate was raised to 200℃ and kept at this temperature for 2 hours for the first sintering. The heating rate was continued to rise to 900℃ and kept at this temperature for 12 hours for the second sintering. -1 Cool to room temperature to obtain a bulk material;

[0066] (3) The bulk material was crushed in a dry environment for 40 seconds and passed through a 200-mesh sieve to obtain large-particle Na with high capacity and high circulation. 0.835 Ni 0.415 Mn 0.585 O2-P2 / O3 composite phase positive electrode material.

[0067] Example 4

[0068] A method for preparing a P2 / O3 composite phase sodium ion battery positive electrode material comprises the following steps:

[0069] (1) Accurately weigh 2 mol Ni 0.33 Mn 0.67 (OH)2 precursor, 4 molNi 0.5 Mn 0.5 (OH)2 precursor, 2.457 mol Na2CO3 sodium salt, the precursor and sodium salt are mixed in a high-speed mixer at a stirring rate of 10000 r min -1 , the stirring time is 1 minute, the cooling time after stirring is 10 minutes, and this is repeated 3 times to obtain a mixed material; the molar ratio of Na / TM is 4.914 / 6=0.8190; TM is the total transition metal (Ni, Mn) content;

[0070] (2) Introduce pure oxygen atmosphere (≥98%) and control the air flow rate to 1.08m 3 h -1 , at 3℃min -1 The heating rate was raised to 200℃ and kept at this temperature for 2 hours for the first sintering. The heating rate was continued to rise to 900℃ and kept at this temperature for 12 hours for the second sintering. -1 Cool to room temperature to obtain a bulk material;

[0071] (3) The bulk material was crushed in a dry environment for 40 seconds and passed through a 200-mesh sieve to obtain large-particle Na with high capacity and high circulation. 0.891 Ni 0.444 Mn 0.556 O2-P2 / O3 composite phase positive electrode material.

[0072] Example 5

[0073] A method for preparing a P2 / O3 composite phase sodium ion battery positive electrode material comprises the following steps:

[0074] (1) Accurately weigh 1 mol of Ni 0.33 Mn 0.67 (OH)2 precursor, 4 molNi 0.5 Mn 0.5 (OH)2 precursor, 2.452 mol Na2CO3 sodium salt, the precursor and sodium salt are mixed in a high-speed mixer at a stirring rate of 10000 r min -1 , the stirring time is 1 minute, the cooling time after stirring is 10 minutes, and this is repeated 3 times to obtain a mixed material; the molar ratio of Na / TM is 4.904 / 5=0.9808; TM is the total transition metal (Ni, Mn) content;

[0075] (2) Introduce pure oxygen atmosphere (≥98%) and control the air flow rate to 1.08m 3 h -1 , at 3℃min -1 The heating rate was raised to 200℃ and kept at this temperature for 2 hours for the first sintering. The heating rate was continued to rise to 900℃ and kept at this temperature for 12 hours for the second sintering. -1 Cool to room temperature to obtain a bulk material;

[0076] (3) The bulk material was crushed in a dry environment for 40 seconds and passed through a 200-mesh sieve to obtain large-particle Na with high capacity and high circulation. 0.934 Ni 0.466 Mn 0.534 O2-P2 / O3 composite phase positive electrode material.

[0077] Comparative Example 1

[0078] A method for preparing a positive electrode material for a sodium ion battery comprises the following steps:

[0079] (1) Accurately weigh 5 mol Ni 0.5 Mn 0.5 (OH)2 precursor, 2.625 mol Na2CO3 sodium salt, the precursor and sodium salt are mixed in a high-speed mixer at a stirring rate of 10000 r min -1 , the stirring time is 1 minute, the cooling time after stirring is 10 minutes, and this is repeated 3 times to obtain a mixed material; the molar ratio of Na / TM is 5.250 / 5=1.050; TM is the total transition metal (Ni, Mn) content;

[0080] (2) Introduce pure oxygen atmosphere (≥98%) and control the air flow rate to 1.08m 3 h -1 , at 3℃min -1 The heating rate was raised to 200℃ and kept at this temperature for 2 hours for the first sintering. The heating rate was continued to rise to 900℃ and kept at this temperature for 12 hours for the second sintering. -1 Cool to room temperature to obtain a bulk material;

[0081] (3) The bulk material was crushed in a dry environment for 40 seconds and passed through a 200-mesh sieve to obtain large-particle NaNi with high capacity and high circulation. 0.5 Mn 0.5 O2-P2 / O3 composite phase positive electrode material.

[0082] Performance testing and result analysis:

[0083] Micromorphology analysis:

[0084] The positive electrode materials prepared in Examples 1-5 and Comparative Example 1 were analyzed by field emission scanning electron microscopy (SEM). The results are as follows: Figure 1 As shown. Figure 1 It can be seen that in the primary particles of the composite phase positive electrode material, the small block-shaped primary particles representing P2 and the long strip-shaped primary particles representing O3 combine with each other to form secondary composite phase particles, indicating that the composite phase has been successfully sintered. Figure 1 As can be seen, the spherical morphology of the composite secondary spheres changes with different ratios, forming larger single crystal particles. The size of the single crystals decreases with increasing O3 phase content, until P2:O3 = 4:1, where larger single crystal particles are produced. Due to the different composite phase ratios, the bulk material samples of Example 5 and Comparative Example 1 have similar morphologies, both exhibiting agglomerated secondary particle morphology. This demonstrates that the present invention effectively regulates the morphology of P2 / O3 composite cathode materials, a key factor in significantly improving electrochemical performance.

[0085] Structural analysis:

[0086] The X-ray diffractometer (XRD) analysis of Examples 1-5 and Comparative Example 1 was performed, and the results were as follows: Figure 2 As shown. Figure 2 It can be seen that the composite phases at all temperatures after regulating the single phase sintering have a good P2 phase peak shape (P63 / mmc space group) and a high sodium O3 phase peak shape (R3m space group); the diffraction peaks are relatively sharp and the peak intensity is relatively large, indicating that the material has good crystallinity, and no impurity peaks appear in the composite phase samples sintered at all ratios, indicating that the prepared materials are all pure phases of a single component. The XRD patterns of the two samples of Example 2 and Comparative Example 1 were structurally refined using Fullprof software, and the specific parameters are shown in Table 1. As can be seen from Table 1, the a-axis and c-axis parameters of the sample of Example 2 are significantly smaller than those of Comparative Example 1, and the c / a values ​​of the two are similar, indicating that both samples have good layered structures. The c / a value of the sample of Example 2 is smaller than the c / a value of Comparative Example 1, indicating that this method can effectively improve the cationic order of the material.

[0087] Table 1 Crystal structure parameters of samples of Example 2 and Comparative Example 1

[0088]

[0089] Electrochemical performance analysis:

[0090] After assembling the positive electrode materials prepared in Example 2 and Comparative Example 1 into CR2032 button half-cells, the initial capacity, cycle performance and rate performance of the batteries were tested at room temperature (25°C). The results are as follows: Figure 3-5The initial gram capacity test conditions are: 0.1C, 2.8~4.0V; the cycle performance test conditions are: 1C (150mAg -1 ) cycled for 100 cycles and measured its capacity retention rate. The details are shown in Table 2-3. Figure 3-4 As shown in Table 2, when tested at room temperature, the sample of Example 2 has a capacity of 124.4 mAh g -1 The high discharge specific capacity, the first coulombic efficiency is as high as 98.2%, and the 1C discharge capacity is as high as 111.7mAh g -1 , slightly lower than the sample in comparative example 1; Example 2 shows excellent cycle performance, with a retention rate of 93.9% after 100 cycles at 1C current, which is significantly higher than the 75.9% of the sample in comparative example 1. Figure 5 As shown in Table 3, the retention rates of the sample in Example 2 at different currents are all higher than those in Comparative Example 1, with a 5C retention rate of 82.0%, while that of Comparative Example 1 is only 70.9%. In summary, the first efficiency, cycle stability, and rate performance of the composite phase material prepared by the present invention are significantly superior to those of the single-phase O3 material in the comparative example.

[0091] Table 2 Capacity and cycle performance of the positive electrode materials prepared in Example 2 and Comparative Example 1 at 25°C

[0092]

[0093] Table 3 Positive electrode materials prepared in Example 2 and Comparative Example 1

[0094]

[0095] Advantages of the implementation of the present invention: The present invention adopts a special one-step controllable sintering process to prepare large-grained single-crystal P2 / O3 composite phase positive electrode materials with good crystal structure and morphology under appropriate sintering temperature (900°C). The present invention effectively reduces the synthesis temperature of single-crystal P2 / O3 composite phase positive electrode materials, and the prepared submicron-level materials have good dispersibility, effectively overcoming the characteristics of the traditional method that the composite phase is difficult to synthesize. The obtained material has good morphology, good particle size consistency, good crystallinity, low transition metal ion mixing, high first coulomb efficiency, high discharge specific capacity, and good cycle performance. The entire production process has a short cycle, a simple process, and is easy to promote industrialization.

[0096] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A method for preparing a P2 / O3 composite phase sodium ion battery cathode material, characterized in that: The chemical formula of the P2 / O3 composite phase sodium ion battery cathode material is Na x Ni y Mn z O2, of which 0.67 <x<1,0.33<y<0.5,0.5<z<0.67; The preparation method comprises the following steps: S1. Mixing a nickel-manganese binary precursor and a sodium salt to obtain a mixed material; S2. In an oxygen atmosphere, the mixed material is subjected to a first sintering, and then the temperature is raised to perform a second sintering, and after cooling in the furnace, a block material is obtained; S3. Mechanically crushing and disintegrating the bulk material, and sieving it to obtain a P2 / O3 composite phase sodium ion battery positive electrode material.

2. The method for preparing the P2 / O3 composite phase sodium ion battery positive electrode material according to claim 1, characterized in that: The total proportion of the P2 phase and the O3 phase in the P2 / O3 composite phase sodium ion battery positive electrode material is 100%, and the molar ratio of the P2 phase to the O3 phase is 4:1, 2:1, 1:1, 1:2 or 1:

4.

3. The method for preparing the P2 / O3 composite phase sodium ion battery positive electrode material according to claim 2, characterized in that: The space group of the P2 phase is P63 / mmc, and the space group of the O3 phase is R3m.

4. The method for preparing the P2 / O3 composite phase sodium ion battery positive electrode material according to claim 1, characterized in that: In step S1 , the amount of Ni in the nickel-manganese binary precursor is 33-50% of the total amount of Ni and Mn; the amount of Mn in the nickel-manganese binary precursor is 50-67% of the total amount of Ni and Mn.

5. The method for preparing the P2 / O3 composite phase sodium ion battery positive electrode material according to claim 1, characterized in that: In step S1, the nickel-manganese binary precursor includes at least one of nickel-manganese oxide, nickel-manganese carbonate, nickel-manganese sulfate, and nickel-manganese hydroxide; and the sodium salt includes at least one of sodium oxide, sodium peroxide, sodium hydroxide, sodium carbonate, and sodium bicarbonate.

6. The method for preparing the P2 / O3 composite phase sodium ion battery positive electrode material according to claim 1, characterized in that: In step S1, the mixing process is as follows: placing the nickel-manganese binary precursor and the sodium salt in a stirring device, stirring at 10,000-20,000 rpm for 1-3 minutes at 5-30° C., cooling for 5-30 minutes, and repeating 1-5 times.

7. The method for preparing a P2 / O3 composite phase sodium ion battery cathode material according to claim 1, characterized in that: In step S2, the oxygen intake flow rate is 0.3-6m 3 h -1 ; The oxygen content of the first sintering is ≥98%.

8. The method for preparing the P2 / O3 composite phase sodium ion battery cathode material according to claim 1, characterized in that: In step S2, the heating rate of the first sintering is 1-5°C min -1 , the temperature is 200-400℃, the time is 1-4h; the cooling rate is 1-10℃min -1 The heating rate of the second sintering is 1-5℃min -1 , temperature is 800-950℃, time is 8-12h.

9. A P2 / O3 composite phase sodium ion battery positive electrode material prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the P2 / O3 composite phase sodium ion battery cathode material according to claim 9 in a sodium ion battery.

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