Crystal plane exposed high-entropy layered oxide cathode material, preparation method and application thereof

Abstract

This invention discloses a high-entropy layered oxide cathode material with exposed crystal faces, its preparation method, and its application, belonging to the field of sodium-ion battery technology. Specifically, this invention prepares the cathode material via a co-precipitation-two-step annealing method, controlling the proportion of multiple metal components and the annealing process to induce large-area exposure of {010} crystal faces (45%–65%). This material utilizes Cu… 2+ Ti 4+ The synergistic introduction of M element introduces high configurational entropy, enhances lattice stability, and effectively suppresses the irreversible transformation of the layered structure to spinel or rock salt phases during sodium ion insertion / extraction. The resulting material possesses both high structural stability and rapid Na... + The transmission channel has a discharge capacity of over 100 mAh / g at 5C rate, significantly improving the cycle life and rate performance of sodium-ion batteries. Moreover, the manufacturing process is simple and suitable for mass production.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, and particularly relates to a high-entropy layered oxide cathode material with exposed crystal faces, its preparation method, and its application. Background Technology

[0002] Among numerous energy storage technologies, sodium-ion batteries (SIBs) have become one of the most promising alternatives to lithium-ion batteries due to their abundant resources and low cost. The cathode material of sodium-ion batteries is one of the key factors determining their electrochemical performance. Currently, the main technical routes for cathode materials include layered transition metal oxides, Prussian blue analogues, and polyanionic compounds. Among these, manganese-based layered oxides (such as Na+) are particularly promising. x MnO2 has become a research hotspot for sodium-ion battery cathode materials due to its high specific capacity, abundant resources, simple synthesis methods, environmental friendliness, and low cost. P2-type manganese-based basal oxides, with their high theoretical capacity and abundant raw materials, have become one of the most promising candidates for sodium-ion battery cathode materials. However, the P2-O2 phase transition that occurs in this material at high voltages (>4.0V), and the slow sodium-ion diffusion kinetics caused by the ordered arrangement of Na / vacancies, directly affect the rate performance and long-cycle stability of the battery, thus limiting its application in full-cell batteries.

[0003] Studies have shown that the ion transport kinetics and structural stability of layered oxide materials are closely related to the exposed crystal facets. For P2-type layered oxides, sodium ion insertion / extraction and migration mainly occur along directions parallel to specific crystal facets. Among these, the {010} crystal facet, due to its open atomic arrangement, provides a rapid transport channel for sodium ions, significantly reducing the sodium ion insertion / extraction barrier and increasing the ion diffusion rate. However, the {010} crystal facet in P2-type layered oxides has a relatively high surface energy. Under conventional preparation processes, high surface energy crystal facets are easily covered by low surface energy crystal facets during crystal growth, resulting in a very low exposure ratio of the {010} crystal facet. This makes it difficult to fully utilize its ion transport advantages, becoming a key bottleneck restricting the improvement of the electrochemical performance of P2-type materials.

[0004] High-entropy materials are a class of single-phase materials containing five or more elements that are solidly dissolved in each other at equimolar or near-molar ratios. They exhibit unique effects in thermodynamics, kinetics, microstructure, and properties, namely high-entropy effect, hysteresis diffusion effect, and lattice distortion effect.

[0005] Therefore, it is of great significance to combine the advantages of high-entropy material composition design, optimize the structural characteristics of P2 phase layered materials for sodium-ion batteries, and develop sodium battery cathode materials with high rate capability and long lifespan. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a high-entropy layered oxide cathode material with exposed crystal faces, its preparation method, and its applications. The high-entropy layered oxide cathode material prepared by this invention can reduce irreversible phase transitions during cycling and improve cycle stability.

[0007] To achieve the above objectives, the present invention proposes the following technical solution: In a first aspect, embodiments of the present invention provide a high-entropy layered oxide cathode material with exposed crystal planes (i.e., a high-entropy P2-type layered oxide cathode material), the general chemical formula of which is: Na x Ni y Mn z Cu a Ti b M c O2; Wherein, M is at least one of Sn, Zr, Zn and Mg; 0.6≤x≤1; 0.15≤y<0.4, 0.2≤z≤0.8, 0.02<a≤0.4, 0<b≤0.2, 0<c≤0.3, y+z+a+b+c=1.

[0008] Beneficial Effects: This invention improves the cycle performance of sodium-ion batteries made from manganese-based transition metal oxide materials by incorporating specific types and proportions of metal elements to increase the material's configurational entropy and reduce phase transitions. Specifically, this invention mainly improves the cycle performance of sodium-ion batteries made from manganese-based transition metal oxide materials by incorporating specific types and proportions of metal elements. 2+ Mg 2+ Ti 4+ The presence of metal ions increases the configurational entropy of the material, producing a significant high-entropy effect, enhancing lattice stability, effectively reducing lattice distortion energy, and strengthening the bonding strength of the transition metal layer. This effectively suppresses the formation of Na+. + Phase transitions during intercalation / delamination lead to localized chemical disorder, increasing the phase transition energy barrier and blocking irreversible phase transition pathways. Specifically, this suppresses the irreversible transformation of the layered structure to spinel or rock salt phases during cycling, resulting in excellent cycle life and rate performance, and enhanced sodium storage capacity. Furthermore, by controlling the content of each metal element (x, y, z, a, b, c) within a defined range, the interactions between atoms in the transition metal layer prevent layer slippage and structural collapse during charging and discharging, thus maintaining the stability of the transition metal layer and reducing irreversible phase transitions.

[0009] Optionally, the high-entropy P2-type layered oxide cathode material has a layered crystal structure, belongs to the hexagonal crystal system, has a space group of P63 / mm, and its primary particle thickness is 0.5~8μm and its width is 0.5~10μm.

[0010] Optionally, the primary particles of the high-entropy P2-type layered oxide cathode material are polyhedra with exposed {010} crystal faces, and the area ratio of the {010} crystal faces is >45%, specifically 45% to 65%.

[0011] Secondly, this invention discloses a method for preparing the above-mentioned high-entropy P2-type layered oxide cathode material, which is prepared using a co-precipitation-annealing process. The specific steps are as follows: First, a nickel-manganese oxide precursor is prepared, and then the nickel-manganese oxide precursor, sodium source compound, copper source compound, titanium source compound and M source compound are mixed and subjected to a two-step annealing treatment in a dry air atmosphere to obtain the high-entropy P2 type layered oxide cathode material.

[0012] Optionally, the preparation process of the nickel-manganese oxide precursor is as follows: S1. Mix the soluble salts of manganese and nickel with water to obtain a mixed salt solution. S2. Under an inert atmosphere, add the mixed salt solution, sodium hydroxide solution and complexing agent solution to the reaction vessel, mix thoroughly, and control the amount of sodium hydroxide and complexing agent to maintain the pH value of the mixed system at 8-11.5 to carry out complexation and co-precipitation reaction to obtain precipitate; S3. The precipitate is aged, washed, filtered and dried to obtain a nickel manganese oxide precursor.

[0013] Furthermore, the total molar concentration of nickel and manganese in the mixed salt solution is 1~2 mol·L⁻¹. -1 ; The molar concentration of the complexing agent solution is 0.2~3 mol·L⁻¹. -1 ; The pH of the mixed solution is adjusted by adding sodium hydroxide solution as a pH adjuster, wherein the molar concentration of the sodium hydroxide solution is 0.5–2 mol·L⁻¹. -1 ; The stirring rate for the complexation and coprecipitation reaction is 200–1000 r / min, the temperature is 30–75 °C, and the reaction time is 10–55 h.

[0014] Furthermore, the soluble salt of manganese is a manganese sulfate, chloride, or nitrate; The soluble salt of nickel is a nickel sulfate, chloride, or nitrate. The complexing agent solution is one or more of citric acid solution, ammonia water, ethylenediaminetetraacetic acid, and ethylenediamine; When feeding the mixed salt solution into the reactor, the feed flow rate is 2-4 L / h. -1 ; The feed flow rate of the complexing agent solution is 0.5~3 L·h. -1 ; The feed flow rate of the sodium hydroxide solution (pH adjuster solution) is 1~4 L·h. -1 ; Optionally, the specific steps of the two-step annealing process are as follows: S1. Under a dry air atmosphere, the temperature is increased from the ambient temperature to 400-550℃ at a heating rate of 2-8℃ / min and held at the temperature for 3-6 hours for pre-sintering, i.e., one-step annealing. S2. The temperature is increased to a final sintering temperature of 800-900℃ at a heating rate of 2-8℃ / min and held at the temperature for 12-18h to perform final sintering (i.e., two-step annealing). Then the temperature is naturally cooled to room temperature to obtain the high-entropy P2 type layered oxide cathode material.

[0015] Furthermore, during the two-step annealing process, oxygen-containing gas is continuously introduced into the calcining equipment, and the intake rate of the dry air atmosphere in steps S1 and S2 is 0.5–5 m / s. 3 / h.

[0016] Optionally, the sodium source compound is one or more selected from sodium carbonate, sodium bicarbonate, sodium nitrate, sodium acetate, and sodium fluoride; The copper source compound is one or more of copper oxide, copper sulfate, copper hydroxide, and copper nitrate. The titanium source compound is one or more of titanium dioxide, titanium nitrate, titanium sulfate, tetrabutyl titanate, and titanium trichloride; The M source compound is one or more of the following: oxides, hydroxides, nitrates, carbonates, and sulfates of M.

[0017] Thirdly, embodiments of the present invention provide a sodium-ion battery, including a positive electrode, a negative electrode, and an electrolyte; The positive electrode sheet includes a positive electrode material, which includes the aforementioned high-entropy P2-type layered oxide positive electrode material.

[0018] Optionally, the negative electrode sheet includes a negative electrode material, which includes hard carbon or metallic sodium; The electrolyte comprises a sodium salt and a solvent, wherein the sodium salt comprises at least one of sodium hexafluorophosphate, sodium perchlorate, and sodium trifluoromethanesulfonate; and the solvent comprises at least one of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and fluoroethylene carbonate.

[0019] Fourthly, the present invention also discloses the application of the above-mentioned high-entropy layered oxide cathode material in the preparation of sodium-ion batteries.

[0020] Compared with the prior art, the present invention has the following advantages and technical effects: (1) This invention improves the system configuration entropy by introducing a variety of high-entropy components into the cathode material of nickel-manganese-based NNM sodium-ion batteries, thereby providing high structural stability for the material and significantly reducing volume deformation during cycling; the change in configuration entropy further regulates the thermodynamically stable structure and crystal plane energy of the system, inducing Na + The exposure of the {010} crystal plane in the ion fast transport channel results in the {010} crystal plane area accounting for >45%, providing an efficient channel for rapid ion migration, while solving the problems of structural stability and ion transport kinetics.

[0021] (2) This invention limits the specific ratio of Cu and Ti to form a specific combination, thereby constructing an efficient and stable high-entropy layered structure. Cu 2+ By enhancing the covalent bonding of the TM layer (the transition metal layer of the cathode material) with appropriate ionic radius, electronegativity, and electrochemical activity, interlayer slip and structural collapse can be suppressed, and the specific capacity of the material can be improved. Ti 4+ The stable high-valence state and high-bond energy of Ti-O stabilize the crystal framework and further enhance the structure's resistance to phase transitions. The synergistic effect of these two factors significantly increases the system's configuration entropy. In addition, the specific ratio of Cu and Ti can construct a local chemical disorder environment, compensating for the effects of Cu alone. 2+ The lattice stability limitations caused by doping, and the single Ti 4+ Doping suppresses electron transport, simultaneously improving the material's specific capacity, rate performance, and long-cycle stability.

[0022] (3) The preparation method disclosed in this invention employs a co-precipitation-annealing process. By controlling the solution environment, multiple metal ions in the solution are simultaneously precipitated. A two-step annealing process promotes the large-area exposure of the {010} crystal planes, resulting in a cylindrical cathode material with high reversible capacity, excellent rate performance, and stability. Furthermore, experiments according to this invention show that the high-entropy layered oxide cathode material can achieve a discharge capacity of over 100 mAh / g at 5C.

[0023] (4) The synthesis process disclosed in this invention is simple and suitable for large-scale industrial production. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings: Figure 1 The XRD pattern of the high-entropy layered oxide cathode material prepared in Example 1 is shown below. Figure 2SEM image of the high-entropy layered oxide cathode material prepared in Example 1; Figure 3 The first charge-discharge curves of the samples prepared in Example 1 and Comparative Example 1 of this invention are shown. Figure 4 This is a comparison chart of the rate performance of sodium-ion batteries assembled from samples prepared in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention. Figure 5 This is a comparison chart of the cycle performance of sodium-ion batteries assembled from samples prepared in Example 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0025] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0026] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0027] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0028] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0029] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0030] The high-entropy layered oxide cathode material, its preparation method, and sodium-ion battery of the present invention will be described in detail below.

[0031] The principle involved in this invention is as follows: Configuration entropy (S) in multi-component material systems config It mainly depends on the type of element and its mole fraction, and can be quantified using the following formula: (1) In equation (1), x i and x j These represent the mole fractions of cations and anions, respectively. R It is the gas constant; cation-site represents a cation site, and anion-site represents an anion site; N and M represent statistical symbols.

[0032] The surface energy of different exposed crystal planes in a material is generally related to temperature and the configurational entropy S in the system. config and vibrational entropy S vib The correlation can be expressed by the formula: (2) In equation (2), The surface energy of the material at 0K. A For Helmholtz free energy, T For temperature.

[0033] This shows that the surface energy of a system with simple composition and low entropy is mainly affected by temperature, while the surface energy of a system with many components and high entropy is mainly affected by configuration entropy. This invention achieves large-area exposure of specific {010} crystal planes through the regulation of multi-cation high-entropy components, with the area ratio of {010} crystal planes >45%, thereby improving the stability and electrochemical performance of the electrode material structure.

[0034] To achieve the above objectives, the present invention specifically proposes the following technical solution: This invention provides a high-entropy layered oxide cathode material with exposed crystal planes, whose general chemical formula is: Na x Ni y Mn z Cu a Ti b M c O2; Where M is at least one of Sn, Zr, Zn and Mg, 0.6≤x≤1, 0.15≤y<0.4, 0.2≤z≤0.8, 0.02<a≤0.4, 0<b≤0.2, 0<c≤0.3, and y+z+a+b+c=1.

[0035] In some embodiments of the present invention, 0.65≤x≤1; 0.15≤y≤0.3; 0.03≤a≤0.3; 0.03≤b≤0.1; 0.05≤c≤0.15.

[0036] In some embodiments of the present invention, the high-entropy layered oxide cathode material with exposed crystal faces has a layered crystal structure, belonging to the hexagonal crystal system, with a space group of P63 / mm. The stacking period of the cation layer and oxygen atom layer of this P2 type high-entropy layered oxide cathode material is 2 close-packed O atoms. The interlayer arrangement of the cation triangular prism coordination sites has translational symmetry, ensuring the long-range order of the crystal structure. There are one-dimensional channels between the layers that can accommodate ion migration. The channel size matches the cation radius, providing a structural basis for ion insertion / extraction during the electrode reaction process. Furthermore, the synergistic effect of the multiple cations of the high-entropy components further optimizes the mechanical and electrochemical stability of the crystal structure.

[0037] Regarding Cu, Ti, Ni, and Mn in high-entropy layered oxide cathode materials, using a certain proportion of transition metal element M in combination with Cu, Ti, Ni, and Mn can result in a more stable locally ordered structure, with higher reversible capacity and cycle performance.

[0038] Preferred Cu in the embodiments of the present invention 2+ With Ti 4+ and a specific combination of elements M (M selected from at least one of Sn, Zr, Zn, and Mg), wherein Cu 2+ With appropriate ionic radius, electronegativity, and electrochemical activity, it can not only form strong covalent bonds with transition metals such as Ni and Mn, effectively suppressing the slippage and structural collapse of the transition metal layer during charge and discharge, but also contribute to improving the specific capacity of the material through its own electrochemical activity, compensating for the capacity decay of traditional manganese-based layered oxides during cycling; Ti 4+ The stable high-valence state and high bond energy of Ti-O stabilize the crystal lattice framework and further suppress the irreversible P2-O2 phase transition under high voltage (>4.0V). At the same time, its unique electronic properties can compensate for the limitations of single Cu. 2+ The risk of lattice distortion caused by doping is mitigated, ensuring the long-range order of the crystal structure. Combined with the complementary ionic radius and electronic state modulation effects of M elements (at least one of Sn, Zr, Zn, and Mg), a high-entropy effect synergistically arises from multiple cations. On one hand, this increases the system's configuration entropy, inducing the directional exposure of the {010} highly active ion transport crystal plane, providing an efficient channel for the rapid migration of sodium ions. On the other hand, it constructs a localized chemically disordered environment, compensating for the limitations of single Cu. 2+ The shortcomings in lattice stability caused by doping are alleviated by single Ti. 4+The doping effect suppresses electron transport, ultimately achieving a simultaneous improvement in the specific capacity, rate performance, and long-cycle stability of the cathode material.

[0039] The high-entropy layered oxide cathode material disclosed in this invention has a layered crystal structure with a primary particle thickness of 0.5~8 μm and a width of 0.5~10 μm. Thickness refers to the dimension of the material perpendicular to the layered plane, which can be measured using scanning electron microscopy (SEM) or transmission electron microscopy (TEM); width refers to the lateral dimension of the material in the layered plane direction, which can be characterized using microscopy techniques such as SEM or TEM. It should be noted that the key difference between this invention and traditional metal ion-doped NNM materials is that this invention uses a multi-cation composition design to form a high-entropy solid solution. This composition design can increase the system configuration entropy and induce the formation of Na+. + Exposure of the {010} crystal plane of the fast ion transport channel improves the electrochemical performance of the material; while traditional single metal ion or multi-metal ion doping improves the stability of the crystal structure by increasing the metal-oxygen bond energy, thereby improving the electrochemical performance of the material.

[0040] In addition, this invention provides a method for preparing the above-mentioned high-entropy P2-type layered oxide cathode material, which employs a co-precipitation-annealing process. First, a nickel-manganese hydroxide precursor is prepared. Then, the nickel-manganese hydroxide precursor, sodium source compound, copper source compound, titanium source compound, and M source compound are mixed and calcined under aerobic conditions to obtain the high-entropy P2-type layered oxide cathode material. Specifically, the method includes the following steps: S1. The nickel-manganese hydroxide precursor was prepared by a co-precipitation method, as follows: (1) Mix the soluble salts of manganese and nickel with water to obtain a mixed salt solution; (2) Under an inert atmosphere, add a mixed salt solution, sodium hydroxide solution and complexing agent solution to the reaction vessel, mix thoroughly, and control the amount of sodium hydroxide solution and complexing agent solution to maintain the pH value of the mixed system at 8 to 11.5 to carry out complexation and coprecipitation reaction to obtain precipitate; age, wash, filter and dry the precipitate to obtain nickel manganese hydroxide precursor.

[0041] In some embodiments of the present invention, the total molar concentration of nickel and manganese in the mixed salt solution is 1-2 mol·L⁻¹. -1 The molar concentration of the complexing agent solution is 0.2~3 mol·L⁻¹. -1The pH value of the mixed solution was adjusted by adding sodium hydroxide solution as a pH adjuster, and the molar concentration of the sodium hydroxide solution was 0.5-2 mol / L; the stirring rate of the complexation and coprecipitation reaction was 200-1000 r / min; the temperature of the complexation and coprecipitation reaction was 30-75℃; and the time of the complexation and coprecipitation reaction was 10-55 h.

[0042] In some embodiments of the present invention, the soluble salt of manganese is one or more of manganese sulfate, chloride and nitrate; the soluble salt of nickel is one or more of nickel sulfate, chloride and nitrate; and the complexing agent solution is one or more of citric acid solution, ammonia, ethylenediaminetetraacetic acid and ethylenediamine.

[0043] S2. The nickel-manganese hydroxide precursor is mixed with sodium source compound, copper source compound, titanium source compound and M source compound, and calcined in a dry air atmosphere to obtain a high-entropy P2 type layered oxide cathode material. The specific operation steps are as follows: (1) The nickel manganese hydroxide precursor is uniformly mixed and ground with sodium source compound, copper source compound and titanium source compound to obtain a mixture; (2) Under dry air atmosphere, the temperature is raised from the ambient temperature to 400-550℃ at a heating rate of 2-8℃ / min and held at the temperature for 3-6 hours for pre-sintering; (3) Heat the material to a final sintering temperature of 800-900℃ at a heating rate of 2-8℃ / min and hold it at that temperature for 12-18 hours to perform final sintering. Then, allow it to cool naturally to room temperature to obtain a high-entropy layered oxide cathode material.

[0044] During the annealing process, an oxygen-containing atmosphere is continuously introduced into the calcining equipment used, and the inlet velocity of the dry air atmosphere in step (2) is 0.5 to 5 m / s. 3 / h, the intake rate of the dry air atmosphere in step (3) is 0.5~5m / h. 3 / h; In some embodiments of the present invention, the sodium source compound is one or more of sodium carbonate, sodium bicarbonate, sodium nitrate, sodium acetate, and sodium fluoride; the copper source compound is one or more of copper oxide, copper sulfate, copper hydroxide, and copper nitrate; the titanium source compound is one or more of titanium dioxide, titanium nitrate, titanium sulfate, tetrabutyl titanate, and titanium trichloride; and the M source compound is one or more of oxides of M, hydroxides of M, nitrates of M, carbonates of M, and sulfates of M.

[0045] In some embodiments of the present invention, the grinding method includes ball milling, which is performed using equipment such as a planetary ball mill. The ball milling conditions include a rotation speed of 150~500 r / min and a time of 2~6 h.

[0046] In addition, this invention also provides a sodium-ion battery, including a positive electrode, a negative electrode, and an electrolyte. The positive electrode includes a positive electrode material, which includes the high-entropy layered oxide positive electrode material prepared above.

[0047] In some embodiments of the present invention, the positive electrode material and the negative electrode material refer to active materials, namely positive electrode active materials and negative electrode active materials, which are used to store and release charge during charging and discharging, thereby realizing the electrochemical energy storage and conversion function of the battery.

[0048] In some embodiments of the present invention, the negative electrode sheet includes a negative electrode material, which includes hard carbon or metallic sodium. The electrolyte includes a sodium salt and a solvent. The sodium salt includes at least one of sodium hexafluorophosphate, sodium perchlorate, and sodium trifluoromethanesulfonate. The solvent includes at least one of propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, and fluoroethylene carbonate.

[0049] Unless otherwise specified, "room temperature" in this invention refers to 20-30℃.

[0050] All raw materials used in this invention were purchased from the market.

[0051] The technical solution of the present invention will be further illustrated by the following embodiments.

[0052] Example 1 This embodiment provides a high-entropy layered oxide cathode material for sodium-ion batteries, with the molecular formula Na. 0.67 Ni 0.28 Mn 0.60 Cu 0.05 Ti 0.05 Sn 0.02 O2, the preparation method of which specifically includes the following steps: S1. Weigh out nickel sulfate and manganese sulfate according to the molar ratio Ni:Mn = 0.28:0.60, and dissolve the above raw materials in deionized water to prepare a total nickel-manganese molar concentration of 1 mol·L⁻¹. -1 A nickel-manganese mixed salt solution A; additionally, deionized water was used to prepare a solution with a molar concentration of 1.5 mol·L⁻¹. -1 Sodium hydroxide solution B1 was prepared to have a molar concentration of 2 mol·L⁻¹. -1 Ammonia complexing agent solution B2.

[0053] A nickel-manganese mixed salt solution A was transferred to a reaction vessel. Under a nitrogen atmosphere, an ammonia complexing agent solution B2 was added to the reaction vessel to adjust the pH of the mixed solution to 11.0 ± 0.05. Sodium hydroxide solution B1 was slowly added to the reaction vessel by titration at a stirring speed of 500 r / min. The reaction was carried out for 18 h at a stirring speed of 500 r / min and a temperature of 35 °C. After the reaction was completed, the sample was aged, centrifuged, and vacuum dried to obtain the nickel-manganese hydroxide precursor.

[0054] S2. The nickel-manganese hydroxide precursor was uniformly mixed with sodium carbonate, copper oxide, titanium dioxide, and tin oxide according to the designed molar ratio. The mixture was then ball-milled for 6 hours at 400 r / min using a planetary ball mill to obtain the final mixture. The mixture was then placed in a tube furnace and heated in a dry air atmosphere (air inlet rate 0.5 m). 3 The temperature was increased to 500℃ at a rate of 3℃ / min and held for 6 hours. Then the temperature was increased to 900℃ at a rate of 3℃ / min and held for 12 hours. Finally, the temperature was allowed to cool naturally to room temperature to obtain a high-entropy layered oxide cathode material, which was denoted as Sample 1.

[0055] X-ray diffraction (XRD) analysis of sample 1 showed that it is a P2 structure material with space group P63 / mm. Furthermore, ICP testing revealed that the Na:Ni:Mn:Cu:Ti:Sn ratio was 0.67:0.28:0.60:0.05:0.05:0.02, thus confirming that sample 1 is a Na material with a P2 structure. 0.67 Ni 0.28 Mn 0.60 Cu 0.05 Ti 0.05 Sn 0.02 O2.

[0056] Example 2 This embodiment provides a high-entropy layered oxide cathode material for sodium-ion batteries, with the molecular formula Na. 0.67 Ni 0.25 Mn 0.6 Cu 0.10 Ti 0.03 Sn 0.02 O2. The preparation method differs from Example 1 only in that: in step S1, nickel sulfate and manganese sulfate are weighed in a molar ratio of Ni:Mn = 0.25:0.6, and the above raw materials are dissolved in deionized water to prepare a solution with a total nickel-manganese concentration of 1 mol·L⁻¹. -1 A nickel-manganese mixed salt solution.

[0057] The high-entropy layered oxide cathode material finally prepared in Example 2 of this invention is denoted as Sample 2.

[0058] X-ray diffraction (XRD) analysis of sample 2 showed that it is a P2 structure material with space group P63 / mm. Furthermore, ICP testing revealed that the ratio of Na:Ni:Mn:Cu:Ti:Sn was 0.67:0.25:0.6:0.10:0.03:0.02, thus confirming that sample 2 is a Na material with a P2 structure. 0.67 Ni 0.25 Mn 0.6 Cu 0.10 Ti 0.03 Sn 0.02 O2.

[0059] Example 3 This embodiment provides a high-entropy layered oxide cathode material for sodium-ion batteries, with the molecular formula Na. 0.67 Ni 0.30 Mn 0.62 Cu 0.03 Ti 0.03 Sn 0.02 The preparation method of O2 differs from that in Example 1 only in that: in step S1, nickel sulfate and manganese sulfate are weighed in a molar ratio of Ni:Mn = 0.3:0.62, and the above raw materials are dissolved in deionized water to prepare a solution with a total nickel-manganese concentration of 1 mol·L⁻¹. -1 A nickel-manganese mixed salt solution.

[0060] The high-entropy layered oxide cathode material finally prepared in Example 3 of this invention is designated as Sample 3. X-ray diffraction (XRD) analysis of Sample 3 showed that it is a P2 structure material with space group P63 / mm. Furthermore, ICP testing showed that Na∶Ni∶Mn∶Cu∶Ti∶Sn = 0.67∶0.3∶0.62∶0.03∶0.03∶0.02, thus proving that Sample 2 is a Na with a P2 structure. 0.67 Ni 0.30 Mn 0.62 Cu 0.03 Ti 0.03 Sn 0.02 O2.

[0061] Example 4 This embodiment provides a high-entropy layered oxide cathode material for sodium-ion batteries, with the molecular formula Na. 0.67 Ni 0.20 Mn 0.55 Cu 0.10 Ti 0.05 Sn 0.10The preparation method of O2 differs from that in Example 1 only in that: in step S1, nickel sulfate and manganese sulfate are weighed in a molar ratio of Ni:Mn = 0.2:0.55, and the above raw materials are dissolved in deionized water to prepare a solution with a total nickel-manganese concentration of 1 mol·L⁻¹. -1 A nickel-manganese mixed salt solution.

[0062] The high-entropy layered oxide cathode material finally prepared in Example 4 of this invention is designated as Sample 4. X-ray diffraction (XRD) analysis of Sample 4 showed that it is a P2 structure material with space group P63 / mm. Furthermore, ICP testing showed that Na∶Ni∶Mn∶Cu∶Ti∶Sn = 0.67∶0.20∶0.55∶0.10∶0.05∶0.10, thus proving that Sample 4 is a Na with a P2 structure. 0.67 Ni 0.20 Mn 0.55 Cu 0.10 Ti 0.05 Sn 0.10 O2.

[0063] Example 5 This embodiment provides a high-entropy layered oxide cathode material for sodium-ion batteries, with the molecular formula Na. 0.67 Ni 0.25 Mn 0.58 Cu 0.07 Ti 0.05 Sn 0.05 The preparation method of O2 differs from that in Example 1 only in that: in step S1, nickel sulfate and manganese sulfate are weighed in a molar ratio of Ni:Mn = 0.25:0.58, and the above raw materials are dissolved in deionized water to prepare a solution with a total nickel-manganese concentration of 1 mol·L⁻¹. -1 A nickel-manganese mixed salt solution.

[0064] The high-entropy layered oxide cathode material finally prepared in Example 5 of this invention is denoted as Sample 5.

[0065] X-ray diffraction (XRD) analysis of sample 3 showed that sample 5 is a P2 structure material with space group P63 / mm. Furthermore, ICP testing showed that Na:Ni:Mn:Cu:Ti:Sn = 0.67:0.25:0.58:0.07:0.05:0.05, thus confirming that sample 5 is a Na with a P2 structure. 0.67 Ni 0.25 Mn 0.58 Cu 0.07 Ti 0.05 Sn 0.05 O2.

[0066] Example 6 This embodiment provides a high-entropy layered oxide cathode material for sodium-ion batteries, with the molecular formula Na. 0.67 Ni 0.28 Mn 0.5 Cu 0.08 Zn 0.04 Ti 0.03 Mg 0.03 Sn 0.04 The specific preparation method for O2 is as follows: S1. Weigh out nickel sulfate and manganese sulfate according to the molar ratio Ni:Mn = 0.28:0.52, and dissolve the above raw materials in deionized water to prepare a total nickel-manganese molar concentration of 1 mol·L⁻¹. -1 A nickel-manganese mixed salt solution A; additionally, deionized water was used to prepare a solution with a molar concentration of 1.5 mol·L⁻¹. -1 Sodium hydroxide solution B1 was prepared to have a molar concentration of 2 mol·L⁻¹. -1 Ammonia complexing agent solution B2.

[0067] The nickel-manganese mixed salt solution A was transferred to a reaction vessel. Under a nitrogen atmosphere, ammonia complexing agent solution B2 was added to the reaction vessel, and the pH value of the mixed solution was adjusted to 11.0 ± 0.05. Sodium hydroxide solution B1 was slowly added to the reaction vessel by titration at a stirring speed of 500 r / min. The reaction was carried out for 18 h at a stirring speed of 500 r / min and a temperature of 35 °C. After the reaction was completed, the sample was aged, centrifuged, and vacuum dried to obtain the nickel-manganese hydroxide precursor.

[0068] S2. The nickel-manganese hydroxide precursor was uniformly mixed with Na2CO3, CuO, anatase phase TiO2, MgCO3, ZnO, and SnO according to the designed molar ratio. The mixture was then ball-milled for 6 hours at 400 r / min to obtain the final mixture. The mixture was placed in a tube furnace and heated in a pure air atmosphere (air inlet rate 0.5 m). 3 The temperature was increased to 500℃ at a rate of 3℃ / min and held for 6 hours, then increased to 900℃ at a rate of 3℃ / min and held for 12 hours. Finally, the material was allowed to cool naturally to room temperature, resulting in a high-entropy cathode material, denoted as sample 6.

[0069] X-ray diffraction (XRD) analysis of sample 6 revealed that it is a P2 structure material with space group P63 / mm. Further ICP analysis showed that the ratio of Na:Ni:Mn:Cu:Zn:Ti:Mg:Sn was 0.67:0.28:0.5:0.08:0.04:0.03:0.03:0.04, thus confirming that sample 6 is a high-entropy layered oxide cathode material with a P2 structure for sodium-ion batteries. 0.67 Ni 0.28 Mn 0.5 Cu 0.08 Zn 0.04 Ti 0.03 Mg 0.03 Sn 0.04 O2.

[0070] Example 7 This embodiment provides a high-entropy layered oxide cathode material for sodium-ion batteries, with the molecular formula Na. 0.67 Ni 0.26 Mn 0.54 Cu 0.07 Zn 0.05 Ti 0.03 Mg 0.02 Zr 0.03 The specific preparation method for O2 is as follows: S1. Weigh out nickel sulfate and manganese sulfate according to the molar ratio Ni:Mn = 0.26:0.54, and dissolve the above raw materials in deionized water to prepare a total nickel-manganese molar concentration of 1 mol·L⁻¹. -1 A nickel-manganese mixed salt solution A; additionally, deionized water was used to prepare a solution with a molar concentration of 1.5 mol·L⁻¹. -1 Sodium hydroxide solution B1 was prepared to have a molar concentration of 2 mol·L⁻¹. -1 Ammonia complexing agent solution B2.

[0071] The nickel-manganese mixed salt solution A was transferred to a reaction vessel. Under a nitrogen atmosphere, ammonia complexing agent solution B2 was added to the reaction vessel, and the pH value of the mixed solution was adjusted to 11.0 ± 0.05. Sodium hydroxide solution B1 was slowly added to the reaction vessel by titration at a stirring speed of 500 r / min. The reaction was carried out for 18 h at a stirring speed of 500 r / min and a temperature of 35 °C. After the reaction was completed, the sample was aged, centrifuged, and vacuum dried to obtain the nickel-manganese hydroxide precursor.

[0072] S2. The nickel-manganese hydroxide precursor was uniformly mixed with Na2CO3, CuO, anatase phase TiO2, MgCO3, ZnO, and Zr(CH3COO)4 according to the designed molar ratio. The mixture was then ball-milled for 6 hours at 400 r / min to obtain the final mixture. The mixture was placed in a tube furnace and heated in a dry air atmosphere (air inlet rate 0.5 m). 3 The temperature was increased to 500℃ at a rate of 3℃ / min and held for 6 hours. Then the temperature was increased to 900℃ at a rate of 3℃ / min and held for 12 hours. Finally, the temperature was allowed to cool naturally to room temperature to obtain a high-entropy layered oxide cathode material, which was designated as sample 7.

[0073] Tests showed that sample 7 contained Na. 0.67 Ni 0.26 Mn 0.54 Cu 0.07 Zn 0.05 Ti 0.03 Mg 0.02 Zr 0.03 O2.

[0074] Comparative Example 1 This comparative example provides a low-entropy cathode material for sodium-ion batteries, with the molecular formula Na. 0.67 Ni 0.33 Mn 0.67 O2, the preparation method of which specifically includes the following steps: S1. Weigh out nickel sulfate and manganese sulfate in a molar ratio of Ni:Mn = 1:2, and dissolve the above raw materials in deionized water to prepare a solution with a total nickel-manganese molar concentration of 1 mol·L⁻¹. -1 A nickel-manganese mixed salt solution A; additionally, deionized water was used to prepare a solution with a molar concentration of 1.5 mol·L⁻¹. -1 Sodium hydroxide solution B1 was prepared to have a molar concentration of 2 mol·L⁻¹. -1 Ammonia complexing agent solution B2 was prepared. Nickel-manganese mixed salt solution A was transferred to a reaction vessel. Under a nitrogen atmosphere, ammonia complexing agent solution B2 was added to the reaction vessel, and the pH of the mixed solution was adjusted to 11.0 ± 0.05. Sodium hydroxide solution B1 was slowly added to the reaction vessel by titration at a stirring speed of 500 r / min. The reaction was carried out for 18 h at a stirring speed of 500 r / min and a temperature of 35 °C. After the reaction, the sample was aged, centrifuged, and vacuum dried to obtain the nickel-manganese hydroxide precursor.

[0075] S2. The nickel-manganese hydroxide precursor and Na2CO3 were uniformly mixed according to the designed molar ratio and ball-milled for 6 hours at a speed of 400 r / min to obtain a mixture. The mixture was placed in a tube furnace and heated to 500℃ at a heating rate of 3℃ / min under a dry air atmosphere and held at that temperature for 6 hours. Then, the temperature was increased to 900℃ at a heating rate of 3℃ / min and held at that temperature for 12 hours. Finally, the mixture was allowed to cool naturally to room temperature to obtain a low-entropy cathode material for sodium-ion batteries, which was designated as control sample 1.

[0076] Upon testing, the comparative sample 1 was found to contain Na. 0.67 Ni 0.33 Mn 0.67 O2.

[0077] Comparative Example 2 This comparative example provides a high-entropy cathode material for sodium-ion batteries, with the molecular formula Na. 0.67 Ni 0.28 Mn 0.60 Cu 0.05 Ti 0.05 Sn 0.02 The preparation method of O2 differs from that in Example 1 in that the high-entropy cathode material is synthesized using a solid-state reaction method, specifically including the following steps: Na₂CO₃, NiO, CuO, MnO₂, anatase TiO₂, and SnO₂ were weighed out according to the molar ratio Na∶Ni∶Mn∶Cu∶Ti∶Sn = 0.67∶0.28∶0.60∶0.05∶0.05∶0.02. The raw materials were placed in a planetary ball mill and milled for 6 hours at 400 r / min to obtain precursor powder. The precursor powder was pressed under 20 MPa pressure for 2 minutes to form discs with a diameter of 8 mm, resulting in powder discs. These discs were then placed in a tube furnace and heated to 500 °C at a rate of 2 °C / min in dry air and held at that temperature for 6 hours. The temperature was then increased to 900 °C at a rate of 5 °C / min and held at that temperature for 12 hours. Finally, the temperature was allowed to cool naturally to room temperature to obtain a high-entropy cathode material, designated as control sample 2.

[0078] Upon testing, the comparison sample 2 was found to contain Na. 0.67 Ni 0.28 Mn 0.60 Cu 0.05 Ti 0.05 Sn 0.02 O2.

[0079] Comparative Example 3 This comparative example provides a high-entropy cathode material for sodium-ion batteries, with the molecular formula Na. 0.67 Ni 0.28 Mn 0.60 Cu0.02 Ti 0.02 Sn 0.08 The elemental composition of O2 differs from that of Example 1 in that the chemical ratio of Cu, Ti, and Sn in this high-entropy cathode material is changed, and the material preparation specifically includes the following steps: S1. Weigh out nickel sulfate and manganese sulfate according to the molar ratio Ni:Mn = 0.28:0.6, and dissolve the above raw materials in deionized water to prepare a total nickel-manganese molar concentration of 1 mol·L⁻¹. -1 A nickel-manganese mixed salt solution A; additionally, deionized water was used to prepare a solution with a molar concentration of 1.5 mol·L⁻¹. -1 Sodium hydroxide solution B1 was prepared to have a molar concentration of 2 mol·L⁻¹. -1 Ammonia complexing agent solution B2.

[0080] The nickel-manganese mixed salt solution A was transferred to a reaction vessel. Under a nitrogen atmosphere, ammonia complexing agent solution B2 was added to the reaction vessel, and the pH value of the mixed solution was adjusted to 11.0 ± 0.05. Sodium hydroxide solution B1 was slowly added to the reaction vessel by titration at a stirring speed of 500 r / min. The reaction was carried out for 18 h at a stirring speed of 500 r / min and a temperature of 35 °C. After the reaction was completed, the sample was aged, centrifuged, and vacuum dried to obtain the nickel-manganese hydroxide precursor.

[0081] S2. The nickel-manganese hydroxide precursor was uniformly mixed with Na2CO3, CuO, anatase TiO2, and SnO according to the designed molar ratio. The mixture was then ball-milled for 6 hours at 400 r / min to obtain the final mixture. The mixture was placed in a tube furnace and heated in a dry air atmosphere (air inlet rate 0.5 m). 3 The temperature was increased to 500℃ at a rate of 3℃ / min and held for 6 hours. Then the temperature was increased to 900℃ at a rate of 3℃ / min and held for 12 hours. Finally, the temperature was allowed to cool naturally to room temperature to obtain a high-entropy layered oxide cathode material, which was designated as control sample 3.

[0082] Tests showed that comparison sample 3 contained Na. 0.67 Ni 0.28 Mn 0.60 Cu 0.02 Ti 0.02 Sn 0.08 O2.

[0083] Comparative Example 4 This comparative example provides a high-entropy cathode material for sodium-ion batteries, with the molecular formula Na. 0.67 Ni 0.28 Mn 0.6 Ti 0.05 Sn 0.07The elemental composition of O2 differs from that of Example 1 in that this high-entropy cathode material does not contain Cu, and the chemical proportion of Ti is changed. The material preparation specifically includes the following steps: S1. Weigh out nickel sulfate and manganese sulfate according to the molar ratio Ni:Mn = 0.28:0.6, and dissolve the above raw materials in deionized water to prepare a total nickel-manganese molar concentration of 1 mol·L⁻¹. -1 A nickel-manganese mixed salt solution A; additionally, deionized water was used to prepare a solution with a molar concentration of 1.5 mol·L⁻¹. -1 Sodium hydroxide solution B1 was prepared to have a molar concentration of 2 mol·L⁻¹. -1 Ammonia complexing agent solution B2.

[0084] The nickel-manganese mixed salt solution A was transferred to a reaction vessel. Under a nitrogen atmosphere, ammonia complexing agent solution B2 was added to the reaction vessel, and the pH value of the mixed solution was adjusted to 11.0±0.05. Under the condition of stirring speed of 500 r / min, sodium hydroxide solution B1 was slowly added to the reaction vessel by titration. The reaction was carried out for 18 h under the conditions of stirring speed of 500 r / min and temperature of 35℃. After the reaction was completed, the sample was aged, centrifuged, and vacuum dried to obtain the nickel-manganese hydroxide precursor.

[0085] S2. The nickel-manganese hydroxide precursor was uniformly mixed with Na2CO3, anatase TiO2, and SnO according to the designed molar ratio. The mixture was then ball-milled for 6 hours at 400 r / min to obtain the final mixture. The mixture was placed in a tube furnace and heated in a dry air atmosphere (air inlet rate 0.5 m). 3 The temperature was increased to 500℃ at a rate of 3℃ / min and held for 6 hours. Then the temperature was increased to 900℃ at a rate of 3℃ / min and held for 12 hours. Finally, the temperature was allowed to cool naturally to room temperature to obtain a high-entropy layered oxide cathode material, which was designated as control sample 4.

[0086] Tests showed that comparison sample 4 contained Na. 0.67 Ni 0.28 Mn 0.6 Ti 0.05 Sn 0.07 O2.

[0087] The configurational entropy of the cathode materials prepared in Examples 1-7 and Comparative Examples 1-4 was calculated using formula (1), and the exposed area ratio of the {010} crystal plane in the above cathode materials was calculated using SEM images. The preparation methods, configurational entropy, and crystal plane exposure ratios of the above examples and comparative examples are shown in Table 1.

[0088] Table 1. Preparation methods and crystal face exposure ratios of different samples The following characterization analysis is performed on the samples prepared in each embodiment and comparative example: I. Material Characterization The samples prepared in Examples 1, 2, 3, 4, 5, 6, 7 and Comparative Examples 1, 2, 3, and 4 were characterized.

[0089] (1) X-ray diffraction (XRD) test Figure 1 The image shows the XRD pattern of the high-entropy layered oxide cathode material prepared in Example 1. Figure 1 As can be seen from the data, the high-entropy layered oxide cathode material prepared in Example 1 exhibits the P63 / mm space group of the P2 phase structure, which belongs to the hexagonal crystal system.

[0090] (2) Scanning electron microscopy (SEM) test Figure 2 The image shows a SEM image of the high-entropy layered oxide cathode material prepared in Example 1. As can be seen from the image, the primary particles of the high-entropy layered oxide cathode material prepared in Example 1 have a cylindrical morphology, and the {010} crystal plane has a large exposed area.

[0091] II. Evaluation of Electrochemical Performance (1) Preparation of positive electrode sheet: The positive electrode materials prepared in Examples 1-7 and Comparative Examples 1-4, conductive carbon black (Super P), and binder polyvinylidene fluoride (PVDF) were weighed at a mass ratio of 8:1:1, with a total mass of 0.4 g. They were uniformly dispersed in 300 μL of N-methylpyrrolidone (NMP) solvent and shaken 6 times using a homogenizer to obtain a mixed slurry. The mixed slurry was uniformly coated on the aluminum foil of the positive electrode current collector and vacuum dried overnight at 120°C. The dried electrode sheet was then rolled using a roller press, and the aluminum foil was cut into circular positive electrode sheets with a diameter of 12 mm using a slicing machine. The loading of active material was controlled at 3 mg / cm³. 2 about.

[0092] (2) Assembly of sodium-ion batteries: Assemble the button cell model CR2032, using the above-mentioned positive electrode as the positive electrode, the negative electrode as a metallic sodium sheet, and the electrolyte as 1mol / L NaClO4 (in EC∶PC=1∶1 vol%). Assemble the button cell with other necessary battery components (separator and shell, etc.) in a glove box filled with high-purity argon gas, and control the moisture pressure ≤0.1ppm and the oxygen partial pressure ≤0.1ppm.

[0093] (3) Constant current charge-discharge test: The coin cells assembled from the samples prepared in Examples 1, 2, 3, 4, 5, 6, 7 and Comparative Examples 1, 2, 3, 4 were subjected to performance testing in a voltage window of 2.0~4.3V. Specifically, the charge-discharge performance test was conducted in a battery testing system at room temperature of 25℃ and 1C = 150mA·g -1 The voltage window is 2.0~4.3V, including: the first charge and discharge test at 0.1C; the 500-cycle test at 1C; and the battery rate performance test at 0.1C, 0.2C, 0.5C, 1C, 2C, 5C, and 10C respectively.

[0094] The electrochemical performance test results of the batteries prepared by the above embodiments and comparative examples are shown in Table 2.

[0095] Table 2 Electrochemical performance of batteries made from different samples Figure 3 The first charge-discharge curves of the samples prepared in Example 1 and Comparative Example 1 of this invention are shown. Figure 4 This is a comparison chart of the rate performance of sodium-ion batteries assembled from samples prepared in Example 1, Comparative Example 1, and Comparative Example 2 of the present invention. Figure 5 This is a comparison chart of the cycle performance of sodium-ion batteries assembled from samples prepared in Example 1 and Comparative Example 1 of the present invention.

[0096] By comparing and analyzing Tables 1-2 and... Figures 3-5 We can conclude that: 1) The configurational entropy values ​​of the cathode materials prepared in Examples 1-7 and Comparative Examples 1-4 are positively correlated with the exposure ratio of the {010} crystal plane. The higher the configurational entropy of the prepared layered oxide, the larger the proportion of the {010} crystal plane exposed area. 2) Although Comparative Example 2 introduced a high-entropy component design with multiple cations, and the component design was the same as in Example 1, the solid-state reaction method used for synthesis resulted in greater resistance to crystal plane control compared to the co-precipitation reaction preparation of the precursor followed by secondary annealing in Example 1, thus failing to achieve large-area exposure of the {010} crystal plane. 3) Sodium-ion batteries assembled with cathode materials prepared in Examples 1-7 exhibited higher Na+ content. +The ion diffusion rate is high, and the cycle stability is excellent after 500 cycles at 1C, with a capacity retention rate significantly higher than that of Comparative Example 1; 4) The sodium-ion battery assembled with the cathode material prepared in Example 1 has a discharge capacity retention rate at high rates of 5C and 10C that is much higher than that of Comparative Examples 1-2; 5) The sodium-ion battery assembled with the cathode material prepared in Example 1 has a capacity retention rate significantly higher than that of Comparative Example 3 with low Cu and Ti ratios and Comparative Example 4 without Cu after 500 cycles at 1C.

[0097] In summary, the sodium-ion battery assembled from the high-entropy cathode material prepared by the co-precipitation-annealing process in this embodiment of the invention has high specific capacity, excellent cycle performance (capacity stable after 500 cycles at 1C rate, with a capacity retention rate ≥87.9%), and high rate stability.

[0098] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-entropy layered oxide cathode material with exposed crystal planes, characterized in that, Chemical formula: Na x Ni y Mn z Cu a Ti b M c O2; Wherein, M is at least one of Sn, Zr, Zn and Mg; 0.6≤x≤1； 0.15≤y<0.4, 0.2≤z≤0.8, 0.02<a≤0.4, 0<b≤0.2, 0<c≤0.3, and y+z+a+b+c=1.

2. The high-entropy layered oxide cathode material with exposed crystal planes according to claim 1, characterized in that, The high-entropy layered oxide cathode material has a layered crystal structure, belongs to the hexagonal crystal system, has a space group of P63 / mm, and its primary particle thickness is 0.5~8μm and its width is 0.5~10μm.

3. The high-entropy layered oxide cathode material with exposed crystal planes according to claim 2, characterized in that, The primary particles of the high-entropy layered oxide cathode material are polyhedra with exposed {010} crystal faces, and the area ratio of the {010} crystal faces is 45% to 65%.

4. A method for preparing a high-entropy layered oxide cathode material with exposed crystal planes as described in any one of claims 1-3, characterized in that, Includes the following steps: Nickel-manganese oxide precursors were prepared using a complexation and co-precipitation method. The nickel-manganese oxide precursor is mixed with sodium-source compound, copper-source compound, titanium-source compound and M-source compound; The high-entropy layered oxide cathode material is obtained by performing a two-step annealing process in a dry air atmosphere.

5. The method for preparing the high-entropy layered oxide cathode material with exposed crystal planes according to claim 4, characterized in that, The preparation process of the nickel-manganese oxide precursor is as follows: A mixed salt solution is obtained by uniformly mixing a soluble salt of manganese, a soluble salt of nickel, and water. Under an inert atmosphere, the mixed salt solution, sodium hydroxide solution, and complexing agent solution are added to the reaction vessel and mixed thoroughly. The pH value of the mixed system is controlled at 8 to 11.5 to carry out the complexation and co-precipitation reaction to obtain the precipitate. The precipitate was aged, washed, filtered, and dried to obtain the nickel-manganese oxide precursor.

6. The method for preparing the high-entropy layered oxide cathode material with exposed crystal planes according to claim 5, characterized in that, The total molar concentration of nickel and manganese in the mixed salt solution is 1-2 mol·L⁻¹ -1 ; The molar concentration of the complexing agent solution is 0.2~3 mol·L⁻¹. -1 ; The molar concentration of the sodium hydroxide solution is 0.5–2 mol·L⁻¹. -1 .

7. The method for preparing the high-entropy layered oxide cathode material with exposed crystal planes according to claim 5, characterized in that, The stirring rate for the complexation and coprecipitation reaction is 200–1000 r / min, the temperature is 30–75 °C, and the reaction time is 10–55 h.

8. The method for preparing the high-entropy layered oxide cathode material with exposed crystal planes according to claim 4, characterized in that, The conditions for the two-step annealing process are as follows: First, heat the temperature to 400-550℃ at a heating rate of 2-8℃ / min and hold it at that temperature for 3-6 hours for pre-sintering. The temperature is then increased to 800-900℃ at a heating rate of 2-8℃ / min and held at that temperature for 12-18 hours for final sintering. After cooling, the high-entropy layered oxide cathode material is obtained.

9. The method for preparing the high-entropy layered oxide cathode material with exposed crystal planes according to claim 4, characterized in that, The intake velocity of the dry air atmosphere is 0.5–5 m / s. 3 / h.

10. The application of the high-entropy layered oxide cathode material as described in any one of claims 1-3 in the preparation of sodium-ion batteries.

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