Polyanion doped sodium / potassium ion battery high-entropy positive electrode material and preparation method and application thereof

Abstract

The invention discloses a polyanion doped sodium / potassium ion battery high-entropy positive electrode material and a preparation method and application thereof, and belongs to the technical field of sodium / potassium ion batteries, the chemical formula of the high-entropy positive electrode material is A < 0.5 > Mn < 0.7 > Co < 0.06 > Fe < 0.06 > Cu < 0.06 > Ti < 0.06 > Li < 0.06 > O < 1.85 > S < 0.05 > N < 0.05 > F < 0.05 >; wherein A is K or Na. According to the high-entropy layered oxide positive electrode material and the preparation method thereof, by introducing multiple anions for synergistic doping and combining multiple times of high-temperature quenching and re-burning treatment, the structural stability, the ion diffusion performance and the electrochemical activity of the high-entropy layered oxide positive electrode material are remarkably improved, and the high-entropy layered oxide positive electrode material has highly-uniform anion and cation distribution and a single-phase P63 / mmc layered structure; and the comprehensive performances such as controllable particle size, high specific surface area, long cycle life and excellent rate capability are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium / potassium ion batteries, and more specifically, to a high-entropy cathode material for sodium / potassium ion batteries doped with multiple anions, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, with the large-scale development of renewable energy and the rapid popularization of electric vehicles, the demand for high-performance secondary batteries has been increasing. Lithium-ion batteries (LIBs) have been widely used in the fields of portable electronic devices and electric vehicles due to their high energy density and good cycle life. However, the uneven distribution of lithium resources, rising costs, and geopolitical factors have restricted the further popularization of lithium-ion batteries. In contrast, sodium-ion batteries (SIBs) and potassium-ion batteries (KIBs) have become important research directions to supplement lithium-ion batteries due to their abundant raw materials, low cost, and excellent electrochemical properties.

[0003] In sodium / potassium ion batteries, the performance of the cathode material has a decisive impact on the overall energy density, cycle life, and rate performance of the battery. Traditional sodium / potassium layered oxides (such as Na x MO2, K x MO2, where M is a transition metal) have become one of the early explored cathode materials due to their similar structure to lithium layered oxides. However, such materials generally have problems such as poor structural stability, rapid capacity decay, and insufficient rate performance, which greatly limit their practical applications.

[0004] To improve the performance of cathode materials, researchers have proposed the design strategy of high-entropy materials (HEMs). By introducing multiple metal elements (usually more than five) to form a near-equimolar ratio mixture at lattice sites, high-entropy materials can significantly improve the thermodynamic stability and anti-phase transition ability of the crystal structure and improve the electrochemical performance. Therefore, high-entropy design has been introduced into sodium / potassium layered oxide cathode materials to enhance the cycle stability and rate performance of materials through the synergistic effect of multiple elements.

[0005] In addition to the cationic high-entropy strategy, anion regulation is also considered an effective means to improve material performance. By introducing heteroanion doping, the charge distribution, lattice parameters, electronic structure, and ion diffusion kinetics of materials can be adjusted, thereby further optimizing the electrochemical reaction characteristics of cathode materials. In particular, the electronegativity and size effect of anions play an important role in stabilizing the structure and improving electron / ion conductivity.

[0006] However, current research on the co-doping of polyanions in high-entropy sodium / potassium layered oxide cathode materials is still relatively limited. Traditional methods mainly involve simple mixing doping, which has the following problems: (1) It is difficult to achieve efficient and orderly doping of multiple anions, with low anion introduction efficiency, insufficient controllability of doping degree and material structure, and easy abnormal growth of particles during heat treatment, making it difficult to control particle size, increasing ion diffusion resistance, reducing rate performance and cycle stability, and resulting in limited improvement in the actual performance of the material. (2) It is difficult to achieve uniform distribution of cations and anions, with certain limitations in doping uniformity and doping depth, and prone to local phase separation or crystal defects. (3) Existing preparation technologies have high requirements for atmosphere and equipment, narrow process windows, complex preparation processes, and it is difficult to balance doping effects and material large-scale preparation requirements.

[0007] Therefore, there is an urgent need to develop a new preparation method that can achieve efficient doping of multiple anions, moderate particle size, stable structure and simple process, and can achieve uniform and stable distribution of cations and anions in high-entropy layered oxide cathode materials, so as to further improve the comprehensive performance and application prospects of high-entropy sodium / potassium ion battery cathode materials. Summary of the Invention

[0008] The object of the present invention is to overcome the above-mentioned defects existing in the prior art, and provide an efficient and controllable high-entropy cathode material for sodium / potassium ion batteries with multi-anion doping, its preparation method and application, so as to solve the problems of uneven multi-anion doping, low doping efficiency, poor material structure stability, difficult control of particle size and complex process in the prior art. By introducing multiple anions for co-doping and combining with a multi-step high-temperature quenching and re-firing treatment process based on the electronegativity order of anions, efficient and uniform doping of multiple cations and anions in a single-phase layered oxide structure is achieved, while optimizing the particle size, effectively improving the material structure stability, enhancing the ion migration rate and cycle stability of the material, thereby significantly improving the comprehensive electrochemical performance and practical application potential of high-entropy sodium / potassium ion battery cathode materials.

[0009] To achieve the above object, the technical solution of the present invention is as follows: A preparation method of a high-entropy cathode material for sodium / potassium ion batteries with multi-anion doping, the chemical formula of the high-entropy cathode material is A 0.5 Mn 0.7 Co 0.06 Fe 0.06 Cu 0.06 Ti 0.06 Li 0.06 O 1.85 S 0.05 N 0.05 F 0.05 ; wherein, A is K or Na; the preparation method of the high-entropy cathode material includes the following steps: S1. According to the chemical ratio, mix the alkali metal salt, Mn source, Co source, Fe source, Cu source, Ti source and Li source, and then grind to obtain a mixture powder; S2. Calcinate the mixture powder to obtain a precursor; S3. Dissolve the S source in deionized water, stir to dissolve, and then refrigerate at 5°C to 8°C for 30 min to 50 min to enhance the thermal shock effect during high-temperature quenching, obtaining a mixed solution A; S4. According to the chemical ratio, heat the precursor to 650°C to 950°C, then add it to the mixed solution A and perform quenching treatment at 25°C to 30°C, and then filter and dry; S5. Dissolve the N source in deionized water, stir to dissolve, and then refrigerate at 5°C to 8°C for 30 min to 50 min to enhance the thermal shock effect during high-temperature quenching, obtaining a mixed solution B; S6. According to the chemical ratio, heat the material obtained in step S4 to 650°C to 950°C, then add it to the mixed solution B and perform quenching treatment at 25°C to 30°C, and then filter and dry; S7. Dissolve the F source in deionized water, stir to dissolve, and then refrigerate at 5°C to 8°C for 30 min to 50 min to enhance the thermal shock effect during high-temperature quenching, obtaining a mixed solution C; S8. According to the chemical ratio, heat the material obtained in step S6 to 650°C to 950°C, then add it to the mixed solution C and perform quenching treatment at 25°C to 30°C, and then filter and dry to obtain the quenched material; S9. Sinter the quenched material obtained in step S8 at 300°C to 1500°C for 8 h to 15 h to obtain the sintered material; S10. Repeat the operations of steps S3 to S9 on the sintered material to obtain the high-entropy cathode material; the high-entropy cathode material is a single-phase layered oxide structure with a space group of P63 / mmc, lattice parameters a = 2.8 Å to 3.0 Å, c = 13.8 Å to 14.5 Å; the particle size of the high-entropy cathode material is 5 μm to 20 μm.

[0010] Specifically, the anion doping sequence is carried out in ascending order of electronegativity, that is, the anion doping sequence is S 2- , N 3- , F -, to avoid the prior doping of high electronegativity anions, which makes it difficult to introduce low electronegativity anions, thereby improving the doping efficiency and uniformity; after multiple high-temperature quenching treatments, the material needs to be re-fired to stabilize the structure. Since there is a tendency for particle growth during the re-firing process, the present invention effectively inhibits excessive particle growth by optimizing the re-firing temperature and time, ensuring that the particle size of the obtained material is controlled within the range of 5μm to 20μm, maintaining a high specific surface area and ion migration rate, and further improving the battery rate performance and cycle stability.

[0011] Optionally, in step S1, the particle size of the mixture powder is 5μm to 15μm; the alkali metal salt includes Na2CO3 or K2CO3; the Mn source, the Co source, the Fe source, the Cu source, the Ti source, and the Li source are each at least one of the corresponding transition metal carbonates and oxides.

[0012] Optionally, in step S2, the heating rate of the calcination is 1°C / min to 10°C / min, preferably 3°C / min to 7°C / min, the calcination temperature is 200°C to 1200°C, preferably 700°C to 1000°C, and the calcination time is 3h to 20h, preferably 8h to 12h.

[0013] Optionally, in steps S4, S6, and S8, the drying temperature is 70°C to 180°C, preferably 100°C to 150°C, and the drying time is 5h to 24h, preferably 8h to 12h.

[0014] Optionally, in step S9, the sintering temperature is preferably 500°C to 1000°C, and the sintering time is 8h to 15h.

[0015] Optionally, in step S10, the number of repeated operations is 2 to 20 times, preferably 2 to 8 times.

[0016] Optionally, the S source, the N source, and the F source are respectively the salts corresponding to S 2- , N 3- , F - ; the concentrations of the mixed solution A, the mixed solution B, and the mixed solution C are respectively 0.01mol / L to 2mol / L, preferably 0.05mol / L to 1mol / L.

[0017] The present invention also discloses a high-entropy cathode material for a sodium / potassium ion battery with multi-anion doping prepared by the above preparation method.

[0018] The present invention also discloses the application of a high-entropy cathode material for a sodium / potassium ion battery with multi-anion doping prepared by the above preparation method in a cathode material for a sodium / potassium ion battery.

[0019] Implementing the embodiments of the present invention will have the following beneficial effects: By introducing multiple anions for co-doping and combining multiple high-temperature quenching and re-firing treatments, the present invention significantly improves the structural stability, ion diffusion performance, and electrochemical activity of the high-entropy layered oxide cathode material. The prepared material not only has a highly uniform distribution of anions and cations and a single-phase P63 / mmc layered structure, but also realizes comprehensive performance improvements such as controllable particle size (5μm - 20μm), high specific surface area, long cycle life, and excellent rate performance. Specifically as follows: First, S 2- , N 3- , and F - anions are introduced in sequence according to the order of increasing electronegativity, effectively improving the doping efficiency and uniformity, and optimizing the electronic structure and ion diffusion performance of the material. Secondly, the process of multiple high-temperature quenching and re-firing is adopted, which not only promotes the stable doping of anions, but also inhibits the excessive growth of particles by precisely controlling the re-firing temperature and time, making the particle size of the material stable in the range of 5μm - 20μm, maintaining a high specific surface area and excellent rate performance. At the same time, through the high-entropy design of multiple transition metals, the structural stability and cycle life of the material are enhanced. The overall process flow is simple and highly controllable, with good prospects for large-scale application.

[0020] Compared with the traditional preparation method, the present invention has a simple process and high doping efficiency, can effectively inhibit the structural collapse and performance degradation of the material during long-term cycling, and significantly enhances the practicability and competitiveness of sodium / potassium ion batteries in high energy density and long-life application scenarios. Brief Description of the Drawings

[0021] Figure 1 is the refined X-ray diffraction (XRD) pattern of the final product prepared in Example 1 of the present invention.

[0022] Figure 2 is the scanning electron microscope (SEM) image of the final product prepared in Example 1 of the present invention.

[0023] Figure 3 is the line-scan SEM image of a single particle of the final product prepared in Example 1 of the present invention.

[0024] Figure 4 is the line-scan result image of a single particle of the final product prepared in Example 1 of the present invention.

[0025] Figure 5 is the EDS image of the TEM of the final product prepared in Example 1 of the present invention. Detailed Description of the Embodiments

[0026] The present invention will be further described below in conjunction with specific embodiments, but the present invention is not limited in any way.

[0027] Comparative Example 1 The chemical formula of the high-entropy cathode material of this comparative example is K 0.5 Mn 0.7 Co 0.06 Fe 0.06 Cu 0.06 Ti 0.06 Li 0.06 O 1.9 S 0.1 。

[0028] The preparation method of the high-entropy cathode material of this comparative example includes the following steps: S1. Weigh K2CO3, MnO2, Fe2O3, CuO, TiO2, Co2O3 and Li2O according to the chemical ratio, and place the above metal oxides in an agate mortar for grinding. After grinding for 30 min, a uniform mixture powder is obtained.

[0029] S2. Put the mixture powder into an alumina crucible and place it in the center of a high-temperature tube furnace. Heat it up to 950 °C at a rate of 6 °C / min for one-step calcination, and keep it at this temperature for 12 h to form a preliminary layered oxide structure, obtaining a precursor.

[0030] S3. Dissolve the sulfate salt in deionized water, stir to dissolve it, and then place it in a refrigerator at 5 °C for 30 min to obtain a sulfate salt solution with a concentration of 0.1 mol / L.

[0031] S4. According to the chemical ratio, heat the precursor to 950 °C, then add it to the anion salt solution and carry out quenching treatment at 25 °C, and then filter and dry it at 120 °C for 12 h to obtain the quenched material; S5. Sinter the quenched material obtained in step S4 at 950 °C for 10 h to obtain the sintered material; S6. Repeat the operations of step S3 to step S5 on the sintered material 2 times to obtain the high-entropy cathode material (A-1).

[0032] Comparative Example 2 Compared with Comparative Example 1, the difference in this comparative example is only that: no anion is doped, and the rest are the same as in Comparative Example 1. The chemical formula of the obtained high-entropy cathode material is K 0.5 Mn 0.7 Co 0.06 Fe 0.06 Cu 0.06 Ti 0.06 Li 0.06 O2. (B-1).

[0033] Comparative Example 3 This comparative example is different from Comparative Example 1 only in that: the sulfate salt in Step S3 is replaced with a nitrate salt, and the rest are the same as in Comparative Example 1. The chemical formula of the high-entropy cathode material prepared is K 0.5 Mn 0.7 Co 0.06 Fe 0.06 Cu 0.06 Ti 0.06 Li 0.06 O 1.9 N 0.1 , denoted as A-2.

[0034] Comparative Example 4 This comparative example is different from Comparative Example 1 only in that: the sulfate salt in Step S3 is replaced with a fluoride salt, and the rest are the same as in Comparative Example 1. The chemical formula of the high-entropy cathode material prepared is K 0.5 Mn 0.7 Co 0.06 Fe 0.06 Cu 0.06 Ti 0.06 Li 0.06 O 1.9 F 0.1 , denoted as A-3.

[0035] Comparative Example 5 This comparative example is different from Comparative Example 1 only in that: the sulfate salt in Step S3 is replaced with a phosphate salt, and the rest are the same as in Comparative Example 1. The chemical formula of the high-entropy cathode material prepared is K 0.5 Mn 0.7 Co 0.06 Fe 0.06 Cu 0.06 Ti 0.06 Li 0.06 O 1.9 P 0.1 , denoted as B-2.

[0036] Comparative Example 6 This comparative example is different from Comparative Example 1 only in that: the sulfate salt in Step S3 is replaced with a chloride salt, and the rest are the same as in Comparative Example 1. The chemical formula of the high-entropy cathode material prepared is K 0.5 Mn 0.7 Co 0.06 Fe 0.06 Cu 0.06 Ti 0.06 Li 0.06 O 1.9 Cl0 .1 , denoted as B-3.

[0037] Comparative Example 7 This comparative example is different from Comparative Example 1 only in that: the sulfate in Step S3 is replaced with sulfate and nitrate, and the rest are the same as in Comparative Example 1. The chemical formula of the prepared high-entropy cathode material is K 0.5 Mn 0. Co 0.06 Fe 0.06 Cu 0.06 Ti 0.06 Li 0.0 6O 1.9 B 0.1 ; where B is an equimolar amount of S 2- and N 3- . Denote it as A-4.

[0038] The preparation method of the high-entropy cathode material in this comparative example includes the following steps: S1 - S2, the same as in Comparative Example 1.

[0039] Steps S3 to S5 specifically include the following steps: (1) Dissolve the sulfate in deionized water, stir to dissolve, and then refrigerate at 5°C for 30 min to obtain a sulfate solution with a concentration of 0.1 mol / L.

[0040] (2) According to the chemical ratio, heat the precursor to 950°C, then add it to the sulfate solution and perform quenching treatment at 25°C, and then filter and dry.

[0041] (3) Dissolve the nitrate in deionized water, stir to dissolve, and then refrigerate at 5°C for 30 min to obtain a nitrate solution with a concentration of 0.1 mol / L.

[0042] (4) According to the chemical ratio, heat the material obtained in step (2) to 950°C, then add it to the nitrate solution and perform quenching treatment at 25°C, and then filter and dry.

[0043] (5) Sinter the material obtained in step (4) at 950°C for 10 h to obtain the sintered material.

[0044] S6, the same as in Comparative Example 1.

[0045] Comparative Example 8 This comparative example is different from Comparative Example 1 only in that: the sulfate in Step S3 is replaced with sulfate and fluoride, and the rest are the same as in Comparative Example 1. The chemical formula of the prepared high-entropy cathode material is K 0.5 Mn 0.7 Co 0.06 Fe 0.06 Cu 0.06 Ti 0.06 Li 0.0 6O 1.9 B0.1 ; wherein, B is an equimolar amount of S 2- and F - . Denoted as A-5.

[0046] The preparation method of the high-entropy cathode material of this comparative example includes the following steps: S1 - S2, the same as Comparative Example 1.

[0047] Steps S3 to S5 specifically include the following steps: (1) Dissolve the sulfate salt in deionized water, stir to dissolve and then refrigerate at 5°C for 30 min to obtain a sulfate salt solution with a concentration of 0.1 mol / L.

[0048] (2) According to the chemical ratio, heat the precursor to 950°C, then add it to the sulfate salt solution and perform quenching treatment at 25°C, and then filter and dry.

[0049] (3) Dissolve the fluoride salt in deionized water, stir to dissolve and then refrigerate at 5°C for 30 min to obtain a fluoride salt solution with a concentration of 0.1 mol / L.

[0050] (4) According to the chemical ratio, heat the material obtained in step (2) to 950°C, then add it to the fluoride salt solution and perform quenching treatment at 25°C, and then filter and dry.

[0051] (5) Sinter the material obtained in step (4) at 950°C for 10 h to obtain the sintered material.

[0052] S6, the same as Comparative Example 1.

[0053] Comparative Example 9 Compared with Comparative Example 1, the difference of this comparative example is only that: the sulfate salt in step S3 is replaced with a nitrogen salt and a fluoride salt, and the rest are the same as Comparative Example 1. The chemical formula of the prepared high-entropy cathode material is K 0.5 Mn 0.7 Co 0.06 Fe 0.06 Cu 0.06 Ti 0.06 Li 0.0 6O 1.9 B 0.1 ; wherein, B is an equimolar amount of N 3- and F - . Denoted as A-6.

[0054] The preparation method of the high-entropy cathode material of this comparative example includes the following steps: S1 - S2, the same as Comparative Example 1.

[0055] Steps S3 to S5 specifically include the following steps: (1) Dissolve the nitrogen salt in deionized water. After stirring and dissolving, refrigerate it at 5°C for 30 min to obtain a nitrogen salt solution with a concentration of 0.1 mol / L.

[0056] (2) According to the chemical ratio, heat the precursor to 950°C, then add it to the nitrogen salt solution and perform quenching treatment at 25°C, followed by filtration and drying.

[0057] (3) Dissolve the fluorine salt in deionized water. After stirring and dissolving, refrigerate it at 5°C for 30 min to obtain a fluorine salt solution with a concentration of 0.1 mol / L.

[0058] (4) According to the chemical ratio, heat the material obtained in step (2) to 950°C, then add it to the fluorine salt solution and perform quenching treatment at 25°C, followed by filtration and drying.

[0059] (5) Sinter the material obtained in step (4) at 950°C for 10 h to obtain the sintered material.

[0060] S6. The same as Comparative Example 1.

[0061] Example 1 The difference between this example and Comparative Example 1 is only that: the sulfur salt in step S3 is replaced with sulfur salt, nitrogen salt and fluorine salt, and the rest are the same as Comparative Example 1. The chemical formula of the prepared high-entropy cathode material is K 0.5 Mn 0.7 Co 0.06 Fe 0.06 Cu 0.06 Ti 0.0 6Li 0.06 O 1.85 B 0.15 ; where B is an equimolar amount of S 2- N 3- F - . Denote it as A-7.

[0062] The preparation method of the high-entropy cathode material in this example includes the following steps: S1 - S2. The same as Comparative Example 1.

[0063] Steps S3 to S5 specifically include the following steps: (1) Dissolve the sulfur salt in deionized water. After stirring and dissolving, refrigerate it at 5°C for 30 min to obtain a sulfur salt solution with a concentration of 0.1 mol / L.

[0064] (2) According to the chemical ratio, heat the precursor to 950°C, then add it to the sulfur salt solution and perform quenching treatment at 25°C, followed by filtration and drying.

[0065] (3) Dissolve the nitrogen salt in deionized water. After stirring and dissolving, place it in a refrigerator at 5 °C for 30 min to obtain a nitrogen salt solution with a concentration of 0.1 mol / L.

[0066] (4) According to the chemical ratio, heat the material obtained in step (2) to 950 °C, then add it to the nitrogen salt solution and perform quenching treatment at 25 °C, followed by filtration and drying.

[0067] (5) Dissolve the fluorine salt in deionized water. After stirring and dissolving, place it in a refrigerator at 5 °C for 30 min to obtain a fluorine salt solution with a concentration of 0.1 mol / L.

[0068] (6) According to the chemical ratio, heat the material obtained in step (4) to 950 °C, then add it to the fluorine salt solution and perform quenching treatment at 25 °C, followed by filtration and drying.

[0069] (7) Sinter the material obtained in step (6) at 950 °C for 10 h to obtain the sintered material.

[0070] S6: The same as Comparative Example 1.

[0071] Comparative Example 10 The difference between this comparative example and Example 1 is only that: the molar ratios of S 2- , N 3- , F - are set to 3:1:1, 1:3:1, and 1:1:3 respectively, denoted as B-4, B-5, and B-6 respectively.

[0072] Comparative Example 11 The difference between this comparative example and Comparative Example 7 is only that: the molar ratios of S 2- , N 3- are set to 2:1 and 1:2 respectively, denoted as B-7 and B-8 respectively.

[0073] Comparative Example 12 The difference between this comparative example and Comparative Example 8 is only that: the molar ratios of S 2 ⁻ and F⁻ are set to 2:1 and 1:2 respectively, denoted as B-9 and B-10 respectively.

[0074] Comparative Example 13 The difference between this comparative example and Comparative Example 9 is only that: the molar ratios of N 3- , F - are set to 2:1 and 1:2 respectively, denoted as B-11 and B-12 respectively.

[0075] Comparative Example 14 The chemical formula of the high-entropy cathode material in this comparative example is K 0.5 Mn 0.7(CoFeCuTiLi) 0.3 O 1.9 S 0.1 Among them, the molar ratios of the elements Co, Fe, Cu, Ti, and Li are set to 1:1:1:1:0.5, 1:1:1:1:1.5, and 1:1:1:1:2, respectively, denoted as B-13, B-14, and B-15.

[0076] Example 2 This example illustrates the influence of different M on the preparation of high-entropy cathode materials. Except for using different M elements, the rest are the same as in Example 1.

[0077] The high-entropy cathode material was prepared according to the method of Example 1, and the results are shown in Table 1.

[0078] Table 1

[0079] Example 3 This example illustrates the influence of different anion source ratios on the preparation of high-entropy cathode materials. Except for using different anion source ratios, the rest are the same as in Example 1.

[0080] The high-entropy cathode material was prepared according to the method of Example 1, and the results are shown in Table 2.

[0081] Table 2

[0082] Example 4 This example illustrates the influence of different transition metal source ratios on the preparation of high-entropy cathode materials. Except for using different transition metal source ratios, the rest are the same as in Example 1.

[0083] The high-entropy cathode material was prepared according to the method of Example 1, and the results are shown in Table 3.

[0084] Table 3

[0085] Comparative Example 15 Compared with Example 1, the difference in this comparative example is only that: it is prepared by a simple mixing and doping method, denoted as B-18, and specifically includes the following steps: The preparation method of the high-entropy cathode material in this comparative example includes the following steps: S1. According to the chemical ratio, weigh K2CO3, MnO2, Fe2O3, CuO, TiO2, Co2O3, Li2O, sulfate, nitrate, and fluoride salt, and place the above metal oxides in an agate mortar for grinding. After grinding, a mixture powder is obtained.

[0086] S2. Place the mixture powder in an alumina crucible at the center of a high-temperature tube furnace, heat it at a rate of 6 °C / min to 950 °C for one-step calcination, and keep it at this temperature for 15 h to form a preliminary layered oxide structure, obtaining Material B-18.

[0087] Comparative Example 16 The difference between this comparative example and Example 1 is only that: the order of anion doping is different. First, use a fluoride (F - ) salt solution, then a nitrogen (N 3- ) salt solution, and finally a sulfur (S 2- ) salt solution for doping. Denote it as B-19.

[0088] Comparative Example 17 The difference between this comparative example and Example 1 is only that: omit the refrigeration operations in steps (1), (3), and (5). Dissolve the sulfur salt, nitrogen salt, and fluoride salt in deionized water respectively. After stirring and dissolving, directly obtain the corresponding salt solutions with a concentration of 0.1 mol / L. Denote it as B-20.

[0089] Comparative Example 18 The difference between this comparative example and Example 1 is only that: omit step S6. Denote it as B-21.

[0090] Example 5 This example illustrates the influence of different calcination temperatures on the preparation of the high-entropy cathode material.

[0091] The difference between this example and Example 1 is only that: set the calcination temperatures to 100 °C and 1300 °C respectively, and the rest are the same as in Example 1. Denote them as B-22 and B-23 respectively.

[0092] Example 6 This example illustrates the influence of different precursor heating temperatures in step S4 on the preparation of the high-entropy cathode material.

[0093] The difference between this example and Example 1 is only that: set the precursor heating temperatures to 100 °C and 1100 °C respectively, and the rest are the same as in Example 1. Denote them as B-24 and B-25 respectively.

[0094] Example 7 This example illustrates the influence of different sintering temperatures on the preparation of the high-entropy cathode material.

[0095] The difference between this example and Example 1 is only that: set the sintering temperatures to 100 °C and 1600 °C respectively, and the rest are the same as in Example 1. Denote them as B-26 and B-27 respectively.

[0096] Example 8 In comparison with Example 1, the only difference in this example is that the chemical formula of the high-entropy cathode material in this example is Na 0. 5Mn 0.7 Co 0.06 Fe 0.06 Cu 0.06 Ti 0.06 Li 0.06 O 1.85 S 0.05 N 0.05 F 0.05 。

[0097] The preparation method of the high-entropy cathode material in this example includes the following steps: S1. Weigh Na2CO3, MnO2, Fe2O3, CuO, TiO2, Co2O3 and Li2O according to the chemical ratio, and place the above metal oxides in an agate mortar for grinding. After grinding for 30 minutes, a uniform mixture powder is obtained.

[0098] The rest is the same as in Example 1.

[0099] The effect of this example is the same as that of Example 1.

[0100] Test Example The material prepared in Example 1 was tested. Figure 1 is the refined X-ray diffraction (XRD) pattern of the final product prepared in Example 1 of the present invention; Table 4 shows the material crystal structure parameters obtained by refining the final product prepared in Example 1 of the present invention; Figure 2 is the scanning electron microscope (SEM) image of the final product prepared in Example 1 of the present invention; Figure 3 is the line-scan SEM image of a single particle of the final product prepared in Example 1 of the present invention; Figure 4 is the line-scan result image of a single particle of the final product prepared in Example 1 of the present invention; Figure 5 is the EDS image of the TEM of the final product prepared in Example 1 of the present invention; it can be found that the high-entropy cathode material prepared in Example 1 is a single-phase layered oxide structure, with a space group of P63 / mmc, lattice parameters a = 2.8 Å - 3.0 Å, c = 13.8 Å - 14.5 Å; the particle size is 5 μm - 20 μm.

[0101] Table 4

[0102] A-1 - A-13 and B-1 - B-27, acetylene black, and PVDF were respectively mixed in NMP at room temperature in a mass ratio of 7:2:1 and stirred evenly to prepare the positive electrode slurry. Then, it was coated on aluminum foil, vacuum dried at 120 °C, cooled, and rolled into a positive electrode sheet. The electrolyte was 0.8 M KPF6 dissolved in EC / PC with a volume ratio of 1:1. Finally, the positive electrode sheet, separator (glass microfiber filter paper GF / D produced by whatman company), and metallic potassium were assembled into a half-cell and assembled into a button cell in a glove box and tested on a blue battery test system at room temperature of 25 °C. As shown in Table 5 - 6.

[0103] Table 5

[0104] Table 6

[0105] The above-described embodiments merely represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of this invention patent shall be subject to the appended claims.

Claims

1. A preparation method of a high-entropy cathode material for a sodium / potassium ion battery doped with polyanions, characterized in that, The chemical formula of the high-entropy cathode material is A 0.5 Mn 0.7 Co 0.06 Fe 0.06 Cu 0.06 Ti 0.06 Li 0.06 O 1.85 S 0.05 N 0.05 F 0.05 ; where A is K or Na; The preparation method of the high-entropy cathode material comprises the following steps: S1. According to the chemical ratio, mix an alkali metal salt, an Mn source, a Co source, an Fe source, a Cu source, a Ti source and an Li source, and then grind to obtain a mixture powder; S2. Calcinate the mixture powder to obtain a precursor; S3. Dissolve the S source in deionized water, stir to dissolve, and then refrigerate at 5°C to 8°C for 30 min to 50 min to obtain a mixed solution A; S4. According to the chemical ratio, heat the precursor to 650°C to 950°C, then add it to the mixed solution A and perform quenching treatment at 25°C to 30°C, and then filter and dry; S5. Dissolve the N source in deionized water, stir to dissolve, and then refrigerate at 5°C to 8°C for 30 min to 50 min to obtain a mixed solution B; S6. According to the chemical ratio, heat the material obtained in step S4 to 650°C to 950°C, then add it to the mixed solution B and perform quenching treatment at 25°C to 30°C, and then filter and dry; S7. Dissolve the F source in deionized water, stir to dissolve, and then refrigerate at 5°C to 8°C for 30 min to 50 min to obtain a mixed solution C; S8. According to the chemical ratio, heat the material obtained in step S6 to 650°C to 950°C, then add it to the mixed solution C and perform quenching treatment at 25°C to 30°C, and then filter and dry to obtain the quenched material; S9. Sinter the quenched material obtained in step S8 at 300°C to 1500°C for 8 h to 15 h to obtain the sintered material; S10. Repeat the operations of step S3 to step S9 on the sintered material to obtain the high-entropy cathode material; the high-entropy cathode material has a single-phase layered oxide structure, the space group is P63 / mmc, and the unit cell parameters are a = 2.8 Å to 3.0 Å, c = 13.8 Å to 14.5 Å; The particle size of the high-entropy cathode material is 5 μm to 20 μm.

2. The preparation method of the high-entropy cathode material for sodium / potassium ion batteries doped with polyanions according to claim 1, characterized in that In step S1, the particle size of the mixture powder is 5 μm to 15 μm; The alkali metal salt includes Na2CO3 or K2CO3; The Mn source, the Co source, the Fe source, the Cu source, the Ti source and the Li source are at least one of the carbonates and oxides of their respective corresponding transition metals.

3. The preparation method of the high-entropy cathode material for sodium / potassium ion batteries doped with polyanions according to claim 1, characterized in that, In step S2, the heating rate of the calcination is 1°C / min to 10°C / min, the calcination temperature is 200°C to 1200°C, and the calcination time is 3 h to 20 h; In steps S4, S6 and S8, the drying temperature is 70°C to 180°C, and the drying time is 5 h to 24 h; In step S9, the sintering temperature is 500°C to 1000°C, and the sintering time is 8 h to 15 h; In step S10, the number of times of repeated operation is 2 to 20 times.

4. The preparation method of the high-entropy cathode material for sodium / potassium ion batteries doped with polyanions according to claim 1, characterized in that The S source, the N source, and the F source are the salts corresponding to S 2- , N 3- , F - respectively; The concentrations of the mixed solution A, the mixed solution B and the mixed solution C are 0.01 mol / L to 2 mol / L respectively.

5. A high-entropy cathode material for sodium / potassium ion batteries with polyanion doping, prepared by the preparation method according to any one of claims 1-4.

6. Application of a high-entropy cathode material for sodium / potassium ion batteries with polyanion doping, prepared by the preparation method according to any one of claims 1-4, in a cathode material for sodium / potassium ion batteries.

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