A layered oxide sodium-ion battery cathode material with a p2 / o3 dual-phase intergrowth structure, and a preparation method and application thereof

Abstract

The application discloses a layered oxide sodium-ion battery cathode material with a P2 / O3 dual-phase symbiotic structure and a preparation method and application thereof. a Ni b Mn c Fe d Mg 0.37‑b Ti 0.63‑c‑d O2, wherein 0.7

Description

Technical Field

[0001] This invention belongs to the field of metallic materials technology, specifically relating to a layered oxide sodium-ion battery cathode material with a P2 / O3 dual-phase symbiotic structure, its preparation method, and its application. Background Technology

[0002] With the rapid development of new energy vehicles, the demand for batteries has increased significantly, and resource bottlenecks have gradually emerged. The high cost and uneven distribution of lithium resources limit the large-scale application of lithium-ion batteries. Against this backdrop, sodium-ion batteries, which have a similar working principle to lithium-ion batteries, have gained attention. Sodium resources are abundant in the Earth's crust and widely distributed globally, therefore sodium-ion batteries have enormous potential for large-scale application.

[0003] Currently, the most widely studied layered oxide cathode materials include P2-type and O3-type structures. P2-type materials possess a stable structural framework and good cycle stability, but suffer from low capacity and low energy density. O3-type materials, on the other hand, exhibit higher capacity and energy density, but exhibit worse structural stability, air stability, and cycle stability. The coexistence of P2 and O3 phases can combine the advantages of both. Achieving a rational phase structure configuration and superior electrochemical performance are currently the main research directions. For example, patent CN117038908A discloses a layered oxide composite cathode material, its preparation method, and its application. This material contains expensive cobalt and vanadium elements, resulting in high raw material costs and hindering widespread adoption. Patent CN117913264A discloses an O3 / P2 biphase composite sodium-ion cathode material, its preparation method, and its application. This method involves preparing O3 and P2 phase materials separately, then mixing and further coating them. However, the composite material obtained by this method merely macroscopically mixes the O3 and P2 phases, failing to form a symbiotic structure at the molecular level. Therefore, the stabilizing effect of the P2 phase in the microstructure cannot be realized. Furthermore, the preparation process is cumbersome and unsuitable for industrial production. Therefore, it is necessary to propose a novel sodium-ion battery cathode material with a P2 / O3 biphase symbiotic structure. Summary of the Invention

[0004] To address the aforementioned technical problems, the present invention aims to provide a layered oxide sodium-ion battery cathode material with a P2 / O3 dual-phase symbiotic structure, its preparation method, and its application. This material exhibits high capacity, average discharge voltage, energy density, and good cycle stability in electrochemical performance. Furthermore, it has low raw material costs, a simple synthesis process, and significant application potential.

[0005] To achieve the above-mentioned objectives, the technical solution adopted by the present invention is as follows:

[0006] In the first aspect of the present invention, a layered oxide sodium-ion battery cathode material with a P2 / O3 biphasic symbiotic structure is proposed. The chemical formula of the layered oxide sodium-ion battery cathode material is

[0007] Na a Ni b Mn c Fe d Mg 0.37-b Ti 0.63-c-d O2, where 0.7 < a < 1.0, 0.1 < b < 0.37, 0.3 < c < 0.53, 0.02 < d < 0.1, and a P2 / O3 biphasic structure is formed in-situ.

[0008] In the second aspect of the present invention, a preparation method for a layered oxide sodium-ion battery cathode material with a P2 / O3 biphasic symbiotic structure is proposed. The steps are as follows:

[0009] S1. Mix a sodium source compound, a nickel source compound, a manganese source compound, a iron source compound, a magnesium source compound, and a titanium source compound and perform ball milling to obtain a uniform mixture powder;

[0010] Step S2. Calcinate the mixture powder in an air or pure oxygen atmosphere, and then perform heat preservation treatment to obtain a layered oxide sodium-ion battery cathode material;

[0011] Among them, the sodium source compound, the nickel source compound, the manganese source compound, the iron source compound, the magnesium source compound, and the titanium source compound are all compounds whose products formed under calcination conditions are metal oxides or compounds whose products formed are metal oxides and gases.

[0012] Preferably, in step S2, the mixture powder is heated to 700 - 1000 °C at a heating rate of 1 - 20 °C in an air or pure oxygen atmosphere and heat preservation is carried out for 10 - 30 h to obtain a layered oxide sodium-ion battery cathode material.

[0013] Preferably, in step S2, the mixture powder is heated to 700 - 1000 °C at a heating rate of 1 - 20 °C in an air or pure oxygen atmosphere, heat preservation is carried out for 10 - 20 h, and then cooled to 400 - 800 °C and heat preservation is carried out for 10 - 20 h to obtain a layered oxide sodium-ion battery cathode material.

[0014] Preferably, in step S1, the sodium source compound includes one or more of sodium carbonate, sodium hydroxide, sodium oxide, sodium peroxide, sodium nitrate, sodium acetate, sodium oxalate, and sodium citrate.

[0015] Preferably, in step S1, the nickel source compound includes one or more of nickel oxide, nickel hydroxide, nickel acetate, nickel nitrate, nickel oxalate, and nickel sulfate.

[0016] Preferably, in step S1, the manganese source compound includes one or more of manganese dioxide, manganese trioxide, manganese hydroxide, manganese tetroxide, manganese acetate, manganese nitrate, manganese oxalate, and manganese sulfate.

[0017] Preferably, in step S1, the iron source compound includes one or more of ferric nitrate, ferric hydroxide, ferric oxide, ferric tetroxide, ferrous oxide, ferric chloride, ferric acetate, ferric sulfate, and ferric carbonate.

[0018] Preferably, in step S1, the magnesium source compound includes one or more of magnesium oxide, magnesium acetate, magnesium nitrate, magnesium oxalate, magnesium sulfate, and magnesium carbonate.

[0019] Preferably, in step S1, the titanium source compound includes one or more of titanium dioxide, titanium nitrate, titanium acetate, titanium carbonate, and titanium oxalate.

[0020] In a third aspect of the invention, the invention proposes an application of a layered oxide sodium-ion battery cathode material having a P2 / O3 dual-phase symbiotic structure, wherein the layered oxide sodium-ion battery cathode material is made into a sodium-ion battery cathode sheet, and the sodium-ion battery cathode sheet, together with a separator, an electrolyte, and a sodium-ion battery anode sheet, constitute a sodium-ion battery.

[0021] Beneficial effects:

[0022] This invention proposes a layered oxide cathode material with a P2 / O3 two-phase structure, which exhibits high capacity, average discharge voltage, energy density, and good cycle stability in electrochemical performance. It also has low raw material cost, simple synthesis process, and application potential. Attached Figure Description

[0023] Figure 1 The image shown is the XRD pattern of the target product obtained in Example 1;

[0024] Figure 2 The charge-discharge curves of the sodium-ion battery obtained in Example 1 within the voltage range of 2-4.2V are shown.

[0025] Figure 3 The charge-discharge curves of the sodium-ion battery obtained in Example 1 at a rate of 0.1C are shown.

[0026] Figure 4 This is a graph showing the specific capacity-cycle sequence of the sodium-ion battery obtained in Example 1 at a 1C rate;

[0027] Figure 5 The charge-discharge curves of the sodium-ion battery obtained in Example 2 at a rate of 0.1C are shown.

[0028] Figure 6 The charge-discharge curves of the sodium-ion battery obtained in Example 3 at a rate of 0.5C are shown.

[0029] Figure 7 The charge-discharge curve of the sodium-ion battery obtained in Example 4 at a rate of 0.1C;

[0030] Figure 8 The charge-discharge curve of the sodium-ion battery obtained in Example 5 at a rate of 0.1C;

[0031] Figure 9 The charge-discharge curve of the sodium-ion battery obtained in Example 6 at a rate of 0.1C;

[0032] Figure 10 The XRD pattern of the target product obtained in Comparative Example 1;

[0033] Figure 11 The charge-discharge curve of the sodium-ion battery obtained in Comparative Example 1 at a rate of 0.1C;

[0034] Figure 12 The specific capacity - cycle number graph of the sodium-ion battery obtained in Comparative Example 1 at a rate of 1C. Detailed implementation manners

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the specific implementation manners of the present invention will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings, and other implementation manners can also be obtained.

[0036] The present invention provides a layered oxide cathode material for a sodium-ion battery with a P2 / O3 dual-phase symbiotic structure, and the chemical formula is Na a Ni b Mn c Fe d Mg 0.37-b Ti 0.63-c-d O2 (0.7 < a < 1.0, 0.1 < b < 0.37, 0.3 < c < 0.53, 0.02 < d < 0.1), having a P2 / O3 dual-phase symbiotic structure. In the present invention, the cathode material of the sodium-ion battery has a multi-layered structure of Ni, Mn, Fe, Mg, and Ti, and a two-phase structure is in-situ formed with relatively low-cost metal elements, and the two phases show a symbiotic relationship within the particles.

[0037] The present invention reasonably selects the ratio of each element, and by introducing a relatively stable P2-phase structure with a wider ion transport channel to support and assist the unstable O3-phase structure with poorer kinetics, the formed P2 / O3 dual-phase symbiotic structure material has the advantages of significantly improving the cycle stability and a higher average discharge voltage.

[0038] Preferably, the particle size of the layered oxide sodium-ion battery cathode material is 1–3 μm.

[0039] This invention also proposes a method for preparing a layered oxide sodium-ion battery cathode material with a P2 / O3 dual-phase symbiotic structure. The cathode material is prepared using a solid-state method, and by adjusting the proportions of each element, a certain amount of P2 phase structure is introduced into the O3 phase, forming a two-phase symbiotic structure. The specific preparation steps are as follows:

[0040] S1. The sodium source compound, nickel source compound, manganese source compound, iron source compound, magnesium source compound and titanium source compound are mixed in a molar ratio and ball-milled to obtain a uniform mixture powder.

[0041] It is easy to understand that the molar ratio in step S1 refers to the stoichiometric ratio of each raw material obtained based on the elements in the final layered oxide sodium-ion battery cathode material.

[0042] Preferably, after ball milling, the particle size of the mixture powder is 0.1-3 μm.

[0043] In step S1, the sodium source compound includes one or more of sodium carbonate, sodium hydroxide, sodium oxide, sodium peroxide, sodium nitrate, sodium acetate, sodium oxalate, and sodium citrate.

[0044] In step S1, the nickel source compound includes one or more of nickel oxide, nickel hydroxide, nickel acetate, nickel nitrate, nickel oxalate, and nickel sulfate.

[0045] In step S1, the manganese source compound includes one or more of manganese dioxide, manganese trioxide, manganese hydroxide, manganese tetroxide, manganese acetate, manganese nitrate, manganese oxalate, and manganese sulfate.

[0046] In step S1, the iron source compound includes one or more of the following: ferric nitrate, ferric hydroxide, ferric oxide, ferric tetroxide, ferrous oxide, ferric chloride, ferric acetate, ferric sulfate, and ferric carbonate.

[0047] In step S1, the magnesium source compound includes one or more of magnesium oxide, magnesium acetate, magnesium nitrate, magnesium oxalate, magnesium sulfate, and magnesium carbonate.

[0048] In step S1, the titanium source compound includes one or more of titanium dioxide, titanium nitrate, titanium acetate, titanium carbonate, and titanium oxalate.

[0049] It is easy to understand that in this invention, the raw materials are preferably compounds that generate metal oxides and gases under high temperature conditions, such as suitable oxides, hydroxides, acetates, nitrates, oxalates, carbonates, etc., and the solid products formed by subsequent calcination will not introduce other impurities.

[0050] Step S2: Calcine the mixture powder in air or pure oxygen atmosphere, and then keep it at a constant temperature to obtain the layered oxide sodium-ion battery cathode material.

[0051] In step S2, the calcination process includes one-step calcination and two-step calcination.

[0052] The specific steps of one-step calcination are as follows: the mixed powder is heated to 700-1000℃ in air or pure oxygen atmosphere, the heating rate is 1-20℃, and the temperature is held for 10-30h to obtain layered oxide sodium-ion battery cathode material.

[0053] The specific steps of the two-step calcination are as follows: the mixed powder is heated to 700–1000℃ in air or pure oxygen atmosphere at a heating rate of 1–20℃, held at this temperature for 10–20 hours, and then cooled to 400–800℃ and held for 10–20 hours to obtain layered oxide sodium-ion battery cathode material. Continuing calcination after cooling helps reduce the formation of impurity phases in the material. The cooling process is carried out slowly without external forces (such as external water cooling or air cooling).

[0054] It should be noted that the effects of one-step calcination and two-step calcination are similar, with two-step calcination being a more optimized treatment of one-step calcination.

[0055] The aforementioned layered oxide sodium-ion battery cathode material can be used to fabricate sodium-ion battery cathode sheets. This invention proposes one feasible method: mixing the layered oxide sodium-ion battery cathode material with conductive additives and binders in a solvent. The mass ratio of the layered oxide sodium-ion battery cathode material to the conductive additives and binders can be (7-9.8):(0.1-2):(0.1-1). After coating and drying, a sodium-ion battery cathode sheet is formed. The conductive additives include one or more of Super P, C65, C45, Ketjen Black, and carbon nanotubes. The binders include one or more of polyvinylidene fluoride, sodium alginate, sodium carboxymethyl cellulose, polyacrylic acid, and polyimide. The solvent is N-methylpyrrolidone or deionized water.

[0056] It is easy to understand that the mixing method, the coating method, and the drying method are conventional steps, and the present invention does not limit them.

[0057] Furthermore, the aforementioned layered oxide sodium-ion battery positive electrode material is used in the preparation of sodium-ion batteries. After forming a sodium-ion battery positive electrode sheet using the layered oxide sodium-ion battery positive electrode material, a sodium-ion battery is composed of a sodium-ion battery positive electrode sheet, a separator, an electrolyte, and a sodium-ion battery negative electrode sheet. The electrolyte is a carbonate electrolyte containing sodium salt, with a sodium salt concentration of 0.3–3 mol / L. Preferably, the sodium salt concentration in the electrolyte is 0.1 mol / L.

[0058] Specifically, the solvent of the electrolyte includes one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and fluorinated ethylene carbonate, preferably a mixed solvent of ethylene carbonate, propylene carbonate, and fluorinated ethylene carbonate. The solute of the electrolyte includes one or more of sodium perchlorate, sodium hexafluorophosphate, sodium bis(fluorosulfonyl)imide, sodium bis(trifluoromethanesulfonyl)imide, sodium difluorooxalateborate, and sodium trifluoromethanesulfonate, preferably sodium perchlorate.

[0059] The separator is a conventional separator used in sodium-ion batteries, preferably a separator formed of glass fiber.

[0060] The technical solution of the present invention will be described in detail below with specific embodiments. It should be noted that in the following embodiments, in the sodium-ion battery, the mass ratio of the positive electrode material to the conductive additive and binder is 8:1:1. This is the mass ratio used in laboratory small-scale tests. Its purpose is to reduce the loss of the positive electrode material and test the performance of sodium ions. In industrial production, the positive electrode material can be significantly increased. For example, the mass ratio of the positive electrode material to the conductive additive and binder can be 9.8:0.1:0.1.

[0061] Example 1

[0062] According to the chemical formula Na 0.82 Ni 0.31 Mn 0.47 Fe 0.1 Mg 0.06 Ti 0.06 O2 was used to mix sodium carbonate, nickel oxide, manganese dioxide, ferric oxide, magnesium oxide, and titanium dioxide in stoichiometric proportions, and ball milled to obtain a homogeneous powder. The powder was then transferred to a heat treatment furnace, heated to 900°C at a rate of 5°C / min under an oxygen atmosphere, held for 12 hours, and then cooled to 700°C and held for 12 hours to obtain the target product Na. 0.82 Ni 0.31 Mn 0.47 Fe 0.1 Mg 0.06 Ti 0.06 O2.

[0063] The Na prepared above 0.82 Ni 0.31 Mn 0.47 Fe 0.1 Mg 0.06 Ti 0.06 O2 cathode material, conductive carbon C65, and binder polyvinylidene fluoride are mixed in a mass ratio of 8:1:1, and N-methylpyrrolidone solvent is added. The mass ratio of cathode material to solvent is 4.25:1. After slurry preparation by a mixing machine, coating by a coating machine, and drying, a mixture of O2 cathode material, conductive carbon C65, and polyvinylidene fluoride is obtained.

[0064] Na 0.82 Ni 0.31 Mn 0.47 Fe 0.1 Mg 0.06 Ti 0.06 Sodium-ion battery positive electrode sheet made of O2 material.

[0065] The sodium-ion battery positive electrode and the metallic sodium negative electrode prepared above are used as counter electrodes to assemble a sodium-ion battery.

[0066] Figure 1 The image shows the XRD pattern of the target product obtained in Example 1. The target material synthesized in Example 1 has good crystallinity and exhibits characteristic peaks of two phase structures, P2 and O3, indicating that the target product obtained in Example 1 is a layered oxide with a P2 / O3 dual-phase structure.

[0067] Figure 2 The figure shows the charge-discharge curves of the sodium-ion battery prepared in Example 1 at 0.1C. Figure 2 It can be seen that the charge-discharge curve is smooth and can release a specific capacity of 156 mAh / g within a voltage range of 2 to 4.2V.

[0068] Figure 3 The figure shows the charge-discharge curves of the sodium-ion battery prepared in Example 1 at 0.1C. Figure 3 It can be seen that the charge-discharge curve is smooth and can release a specific capacity of 128mAh / g within a voltage range of 2 to 4V.

[0069] Figure 4 The figure shown is a specific capacity-cycle sequence diagram of the sodium-ion battery prepared in Example 1 at 1C. Figure 4 It can be seen that sodium-ion batteries have good cycle stability, with a capacity retention rate of 92% after 100 cycles.

[0070] Example 2

[0071] According to the chemical formula Na 0.76 Ni 0.31 Mn 0.47 Fe 0.1 Mg 0.06 Ti 0.06 O2 was used to mix the raw materials in stoichiometric proportions, and the remaining preparation methods were the same as in Example 1, to obtain the target product Na. 0.76 Ni 0.31 Mn 0.47 Fe 0.1 Mg 0.06 Ti 0.06 O2, and the target product was used to prepare sodium-ion battery positive electrode and sodium-ion battery in sequence.

[0072] Figure 5The figure shows the charge-discharge curves of the sodium-ion battery prepared in Example 2 at 0.1C. Figure 2 It can be seen that the charge-discharge curve is smooth and can release a specific capacity of 114 mAh / g within the voltage range of 2 to 4V.

[0073] Example 3

[0074] According to the chemical formula Na 0.76 Ni 0.27 Mn 0.53 Fe 0.05 Mg 0.1 Ti 0.05 O2 was used to mix the raw materials in stoichiometric proportions, and the remaining preparation methods were the same as in Example 1, to obtain the target product Na. 0.76 Ni 0.27 Mn 0.53 Fe 0.05 Mg 0.1 Ti 0.05 O2, and the target product was used to prepare sodium-ion battery positive electrode and sodium-ion battery in sequence.

[0075] Figure 6 The figure shows the charge-discharge curves of the sodium-ion battery prepared in Example 3 at 0.5C. Figure 6 It can be seen that the charge-discharge curve is smooth and can release a specific capacity of 105mAh / g within a voltage range of 2 to 4V.

[0076] Example 4

[0077] According to the chemical formula Na 0.82 Ni 0.31 Mn 0.47 Fe 0.1 Mg 0.06 Ti 0.06 O2 was used to mix sodium carbonate, nickel oxide, manganese dioxide, ferric oxide, magnesium oxide, and titanium dioxide in stoichiometric proportions, and ball milled to obtain a homogeneous powder. The powder was then transferred to a heat treatment furnace and heated to 900°C at a rate of 5°C / min under an oxygen atmosphere. The mixture was held at this temperature for 12 hours, then cooled to 750°C and held for another 12 hours to obtain the target product, Na. 0.82 Ni 0.31 Mn 0.47 Fe 0.1 Mg 0.06 Ti 0.06 O2.

[0078] The Na prepared above 0.82 Ni 0.31 Mn 0.47 Fe 0.1 Mg 0.06 Ti 0.06O2 cathode material, conductive carbon C65, and binder polyvinylidene fluoride are mixed in a mass ratio of 8:1:1, and N-methylpyrrolidone solvent is added. The mass ratio of cathode material to solvent is 4.25:1. After slurry preparation by a mixing machine, coating by a coating machine, and drying, a mixture of O2 cathode material, conductive carbon C65, and polyvinylidene fluoride is obtained.

[0079] Na 0.82 Ni 0.31 Mn 0.47 Fe 0.1 Mg 0.06 Ti 0.06 Sodium-ion battery positive electrode sheet made of O2 material.

[0080] The above-prepared positive electrode and metallic sodium negative electrode are used as counter electrodes to assemble a sodium-ion battery.

[0081] Figure 7 The figure shows the charge-discharge curves of the sodium-ion battery prepared in Example 4 at 0.1C. Figure 7 It can be seen that the charge-discharge curve is smooth, and it can release a specific capacity of 128 mAh / g in the voltage range of 2 to 4V, which is close to the data obtained under the same conditions in Example 1.

[0082] Example 5

[0083] According to the chemical formula Na 0.82 Ni 0.31 Mn 0.47 Fe 0.1 Mg 0.06 Ti 0.06 O2 was used to mix sodium carbonate, nickel oxide, manganese dioxide, ferric oxide, magnesium oxide, and titanium dioxide in stoichiometric proportions, and ball milled to obtain a homogeneous powder. The powder was then transferred to a heat treatment furnace and heated to 750°C at a rate of 5°C / min under a pure oxygen atmosphere, and held for 30 hours to obtain the target product Na. 0.82 Ni 0.31 Mn 0.47 Fe 0.1 Mg 0.06 Ti 0.06 O2.

[0084] The Na prepared above 0.82 Ni 0.31 Mn 0.47 Fe 0.1 Mg 0.06 Ti 0.06 O2 cathode material, conductive carbon C65, and binder polyvinylidene fluoride are mixed in a mass ratio of 8:1:1, and N-methylpyrrolidone solvent is added. The mass ratio of cathode material to solvent is 4.25:1. After slurry preparation by a mixing machine, coating by a coating machine, and drying, a mixture of O2 cathode material, conductive carbon C65, and polyvinylidene fluoride is obtained.

[0085] Na 0.82 Ni 0.31 Mn 0.47 Fe 0.1 Mg 0.06 Ti 0.06 Sodium-ion battery positive electrode sheet made of O2 material.

[0086] The above-prepared positive electrode and metallic sodium negative electrode are used as counter electrodes to assemble a sodium-ion battery.

[0087] Figure 8 The figure shows the charge-discharge curves of the sodium-ion battery prepared in Example 5 at 0.1C. Figure 8 It can be seen that the charge-discharge curve is smooth and can release a specific capacity of 120mAh / g within a voltage range of 2 to 4V.

[0088] Example 6

[0089] According to the chemical formula Na 0.82 Ni 0.31 Mn 0.47 Fe 0.1 Mg 0.06 Ti 0.06 O2 was used to mix sodium carbonate, nickel oxide, manganese dioxide, ferric oxide, magnesium oxide, and titanium dioxide in stoichiometric proportions, and ball milled to obtain a homogeneous powder. The powder was then transferred to a heat treatment furnace and heated to 850°C at a rate of 5°C / min in an air atmosphere, and held for 15 hours to obtain the target product Na. 0.82 Ni 0.31 Mn 0.47 Fe 0.1 Mg 0.06 Ti 0.06 O2.

[0090] The Na prepared above 0.82 Ni 0.31 Mn 0.47 Fe 0.1 Mg 0.06 Ti 0.06 O2 cathode material, conductive carbon C65, and binder polyvinylidene fluoride are mixed in a mass ratio of 8:1:1, and N-methylpyrrolidone solvent is added. The mass ratio of cathode material to solvent is 4.25:1. After slurry preparation by a mixing machine, coating by a coating machine, and drying, a mixture of O2 cathode material, conductive carbon C65, and polyvinylidene fluoride is obtained.

[0091] Na 0.82 Ni 0.31 Mn 0.47 Fe 0.1 Mg 0.06 Ti 0.06Sodium-ion battery positive electrode sheet made of O2 material.

[0092] The above-prepared positive electrode and metallic sodium negative electrode are used as counter electrodes to assemble a sodium-ion battery.

[0093] Figure 9 The figure shows the charge-discharge curves of the sodium-ion battery prepared in Example 6 at 0.1C. Figure 9 It can be seen that the charge-discharge curve is smooth and can release a specific capacity of 121mAh / g within a voltage range of 2 to 4V.

[0094] Comparative Example 1

[0095] According to the chemical formula NaNi 0.33 Mn 0.33 Fe 0.34 O2 is used to mix the raw materials in stoichiometric proportions, and the remaining preparation methods are the same as in Example 1, to obtain the target product NaNi. 0.33 Mn 0.33 Fe 0.34 O2, and the target product was used to prepare sodium-ion battery positive electrode and sodium-ion battery in sequence.

[0096] Figure 10 The image shown is the XRD pattern of the target product obtained in Comparative Example 1. Figure 10 It can be seen that the synthesized target material has good crystallinity, and the XRD pattern corresponds to the characteristic peaks of the O3 phase structure, indicating that it is an O3 type structure.

[0097] Figure 11 To compare Example 1, the charge-discharge curves of the sodium-ion battery at 0.1C were obtained. As can be seen from the figure, there is a clear plateau in the charge-discharge curve, indicating that the material may undergo a significant structural phase transition reaction during the charge-discharge process, and it releases a specific capacity of 133 mAh / g in the voltage range of 2-4V.

[0098] Figure 12 The specific capacity-cycle sequence diagram of the sodium-ion battery prepared in Comparative Example 1 at 1C is shown in the figure. As can be seen from the figure, the cycle stability of the synthesized target material is worse than that of Example 1, with a capacity retention of only 77% after 100 cycles, which is 15% lower than that of Example 1.

[0099] Based on the comparison of data from Examples 1-6 and Comparative Example 1, it can be seen that the cathode material prepared by the present invention has a P2 / O3 dual-phase symbiotic structure, which significantly improves cycle stability. It can release a specific capacity of up to 156 mAh / g (2-4.2V) within a voltage range of 2-4.2V. The present invention can generate a P2 / O3 dual-phase structure in situ. Compared to the O3 phase structure material of Comparative Example 1, the cathode material of the present invention retains 92% of its capacity after 100 cycles at a current density of 1C, which is far higher than the data of Comparative Example 1. This indicates that the cathode material with a P2 / O3 dual-phase structure prepared by the present invention helps to suppress harmful phase transitions, improve structural stability, and enhance probabilistic electrochemical performance.

[0100] This invention uses a two-step calcination method to prepare cathode materials. Due to the low-temperature calcination in the second stage, the cathode materials have better crystallinity, better electrochemical performance, and can release higher capacity.

[0101] The embodiments provided by the present invention have been described in detail above. Specific examples have been used to illustrate the principles and implementation methods of the present invention, and the descriptions of the embodiments above are only for the purpose of helping to understand the core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A layered oxide sodium-ion battery cathode material with a P2 / O3 dual-phase symbiotic structure, characterized in that, The chemical formula of the layered oxide sodium-ion battery cathode material is Na a Ni b Mn c Fe d Mg 0.37-b Ti 0.63-c-d O2, where 0.7 < a < 1.0, 0.1 < b < 0.37, 0.3 < c < 0.53, 0.02 < d < 0.1, and a P2 / O3 biphasic structure is formed in-situ; The preparation method of layered oxide sodium-ion battery cathode material is as follows: S1. The sodium source compound, nickel source compound, manganese source compound, iron source compound, magnesium source compound and titanium source compound are mixed and ball-milled to obtain a uniform mixture powder; Step S2: Calcine the mixture powder in an oxygen-containing atmosphere, followed by heat treatment to obtain layered oxide sodium-ion battery cathode material; Among them, sodium source compounds, nickel source compounds, manganese source compounds, iron source compounds, magnesium source compounds and titanium source compounds are all compounds that produce metal oxides or compounds that produce metal oxides and gases under calcination conditions. In step S2, the mixed powder is heated to 700-1000°C in air or pure oxygen atmosphere at a heating rate of 1-20°C / min, held at that temperature for 10-20 h, and then cooled to 400-800°C and held at that temperature for 10-20 h to obtain layered oxide sodium-ion battery cathode material.

2. The layered oxide sodium-ion battery cathode material with a P2 / O3 dual-phase symbiotic structure according to claim 1, characterized in that, In step S1, the sodium source compound includes one or more of sodium carbonate, sodium hydroxide, sodium oxide, sodium peroxide, sodium nitrate, sodium acetate, sodium oxalate, and sodium citrate.

3. The layered oxide sodium-ion battery cathode material with a P2 / O3 dual-phase symbiotic structure according to claim 1, characterized in that, In step S1, the nickel source compound includes one or more of nickel oxide, nickel hydroxide, nickel acetate, nickel nitrate, nickel oxalate, and nickel sulfate.

4. The layered oxide sodium-ion battery cathode material with a P2 / O3 dual-phase symbiotic structure according to claim 1, characterized in that, In step S1, the manganese source compound includes one or more of manganese dioxide, manganese trioxide, manganese hydroxide, manganese tetroxide, manganese acetate, manganese nitrate, manganese oxalate, and manganese sulfate.

5. The layered oxide sodium-ion battery cathode material with a P2 / O3 dual-phase symbiotic structure according to claim 1, characterized in that, In step S1, the iron source compound includes one or more of the following: ferric nitrate, ferric hydroxide, ferric oxide, ferric tetroxide, ferrous oxide, ferric chloride, ferric acetate, ferric sulfate, and ferric carbonate.

6. The layered oxide sodium-ion battery cathode material with a P2 / O3 dual-phase symbiotic structure according to claim 1, characterized in that, In step S1, the magnesium source compound includes one or more of magnesium oxide, magnesium acetate, magnesium nitrate, magnesium oxalate, magnesium sulfate, and magnesium carbonate. Titanium source compounds include one or more of titanium dioxide, titanium nitrate, titanium acetate, titanium carbonate, and titanium oxalate.

7. An application of a layered oxide sodium-ion battery cathode material with a P2 / O3 dual-phase symbiotic structure, characterized in that, The layered oxide sodium-ion battery positive electrode material as described in claim 1 is used to make a sodium-ion battery positive electrode sheet, and the sodium-ion battery positive electrode sheet, together with the separator, electrolyte, and sodium-ion battery negative electrode sheet, constitute a sodium-ion battery.

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