A positive electrode material, a preparation method and application thereof, a positive electrode sheet and a sodium ion battery

Abstract

The application discloses a positive electrode material and a preparation method and application thereof, a positive electrode sheet and a sodium ion battery, and the positive electrode material is composed of a spinel phase material coated high-nickel ternary material. The heat stability and high-speed ion channel of the coated spinel phase material are used, so that the positive electrode material greatly improves the gram capacity, cycle stability, reduces the heat release and improves the safety performance while retaining the high pressure and high energy density advantages of the high-nickel ternary material. The electrochemical performance at high voltage is greatly improved. The spinel phase material of pure phase is synthesized on the basis of the ternary material through simple chemical element substitution, and the process is simple. Finally, the capacity density and cycle stability of the positive electrode material are improved through the coating of the spinel phase material on the high-nickel ternary material, and the obtained positive electrode material has higher energy density, better thermal stability and electrochemical performance.

Description

Technical Field

[0001] This invention relates to the field of sodium-ion battery technology, and in particular to a cathode material, its preparation method and application, cathode sheet and sodium-ion battery. Background Technology

[0002] Sodium-ion batteries have been widely used due to their advantages such as low raw material cost, better capacity retention at low temperatures, and excellent rate performance. Layered transition metal oxide materials, with their high specific energy, have become ideal cathode materials for sodium-ion batteries. Among them, nickel-based ternary materials have a relatively high degree of commercialization. Based on different nickel contents, nickel-based ternary materials are divided into high-nickel materials and low-nickel materials. High-nickel materials (such as NCM811 and NCM622) have a higher nickel content and higher specific energy, but their cycle life is inferior to that of low-nickel materials (such as NCM523 and NCM111). At the same time, due to the strong nucleophilicity of the layered transition metal oxide surface, nickel-based ternary materials also suffer from serious interfacial instability and capacity decay problems.

[0003] In related technologies, surface coating methods can be used to improve the electrochemical reaction interface of nickel-based ternary materials, thereby improving the electrochemical performance of the materials. Due to its stable crystal structure and fast electron transport, the spinel phase is a promising coating material for high-nickel ternary cathode materials. However, pure spinel phases (such as Na₂O₃)... 0.44 MnO2 and similar materials are difficult to synthesize simply. Furthermore, in spinel-phase cathode materials under high voltage, Mn ions readily undergo side reactions with the electrolyte, leading to electrolyte decomposition, structural damage, and transition metal dissolution. This negatively impacts cycle stability under high voltage, reduces battery cycle performance, and shortens battery lifespan.

[0004] Therefore, solving the problems of capacity decay, insufficient safety, and poor cycle performance of cathode materials, and improving the safety, stability, and electrochemical performance of materials is of great significance. Summary of the Invention

[0005] This invention aims to solve at least one of the technical problems existing in the prior art. To this end, this invention proposes a cathode material, its preparation method and application, a cathode sheet, and a sodium-ion battery, aiming to solve the problems of capacity decay, insufficient stability, and poor cycle life existing in current cathode materials.

[0006] In a first aspect, the present invention provides a cathode material comprising a matrix material and a spinel phase material, wherein the spinel phase material is coated on at least a portion of the surface of the matrix material.

[0007] The spinel phase material includes Na[(Ni)] a Co b Mnc ) d TM e O₂, where 0.6 ≤ a < 1, 0 < b ≤ 0.2, 0 < c ≤ 0.2, a + b + c = 1 and b = c; 0.8 ≤ d < 1, 0 < e ≤ 0.2, and d + e = 1; TM is selected from at least one of Nb, Bi, Sb, Mo.

[0008] The matrix material includes Na[Ni x Co y Mn z O₂, where 0.6 ≤ x < 1, 0 < y ≤ 0.2, 0 < z ≤ 0.2, and x + y + z = 1.

[0009] The positive electrode material according to the embodiment of the present invention has at least the following beneficial effects: The present invention provides a positive electrode material with a protective layer structure, which is composed of a spinel phase material coating a high-nickel ternary material. This material can protect the positive electrode particles, improve the cycle life, and at the same time can effectively increase the thermal decomposition temperature of the pure high-nickel ternary material, reduce the heat release, and improve the safety performance. The spinel phase material of the present invention is synthesized on the basis of the ternary material, and by adjusting the ratios of Ni, Co, and Mn elements, it can undergo crystal structure changes by doping elements such as Nb, Bi, Sb, Mo, etc., to form a pure-phase spinel phase structure. Since the spinel phase has a stable crystal structure and fast electron transport performance, it can effectively protect the surface of the positive electrode particles from the attack of by-products of the liquid electrolyte, especially HF, and improve the thermodynamic stability of the positive electrode material of the battery layer transition metal oxide and Na + transport kinetics. The present invention utilizes the thermal stability and high-speed ion channels of the coated spinel phase material, so that while retaining the advantages of high voltage and high energy density of the high-nickel ternary material, the specific capacity, cycle stability, and safety performance of the material are greatly improved, and the electrochemical performance at high voltage is greatly improved. Finally, by coating the high-nickel ternary material with the spinel phase material, the present invention simultaneously increases the capacity density and cycle stability of the positive electrode material, and the obtained positive electrode material has higher energy density, better thermal stability, and electrochemical performance.

[0010] In some embodiments of the present invention, 0.8 ≤ a < 1, 0 < b ≤ 0.1, 0 < c ≤ 0.1, a + b + c = 1 and b = c.

[0011] In some embodiments of the present invention, the spinel material is Na[(Ni 0.8 Co 0.1 Mn 0.1 ) 0.9 TM 0.1 O₂, TM is selected from at least one of Nb, Bi, Sb, Mo.

[0012] Specifically, the spinel material can be Na[(Ni 0.8 Co 0.1 Mn 0.1 ) 0.9 Nb 0.1 O2, Na[(Ni 0.8 Co 0.1 Mn 0.1 ) 0.9 Bi 0.1 O2, Na[(Ni 0.8 Co 0.1 Mn 0.1 ) 0.9 Sb 0.1 O2, Na[(Ni 0.8 Co 0.1 Mn 0.1 ) 0.9 Mo 0.1 One of the O2 components.

[0013] In some embodiments of the present invention, the matrix material is Na[Ni]. 0.8 Co 0.1 Mn 0.1 O2.

[0014] In some embodiments of the present invention, the mass ratio of the spinel phase material to the mass of the cathode material is 0.5% to 10%.

[0015] In this invention, the coating amount of spinel phase material needs to be controlled within a reasonable range. This is because as the coating amount increases, the thermal stability of the cathode material also improves significantly, but excessive coating will significantly reduce the energy density. This invention ultimately controls the mass ratio of spinel phase material to the mass of the cathode material to be 0.5%-10%. Within this coating ratio range, the cathode material exhibits better thermal stability and cycle stability, while also possessing a higher energy density.

[0016] In some preferred embodiments of the present invention, the mass ratio of the spinel phase material to the mass of the cathode material is 0.5% to 5%.

[0017] A second aspect of the present invention provides a method for preparing the above-mentioned cathode material, comprising the steps of:

[0018] S1. Provide sodium source, inducing material and high-nickel ternary precursor material, mix them evenly by ball milling, and then sinter them at high temperature to obtain spinel phase material;

[0019] S2. The spinel phase material and the matrix material are mixed evenly by ball milling, and then sintered twice to obtain the cathode material.

[0020] The method for preparing the cathode material according to embodiments of the present invention has at least the following beneficial effects: The preparation method of the present invention first synthesizes a spinel phase material using a sodium source, an inducing material, and a high-nickel ternary precursor material. Then, the obtained spinel phase material is used as a coating material to coat the matrix material, thereby obtaining the cathode material. The synthesis of the spinel phase material is very simple, obtained through simple chemical element substitution: the spinel phase material is synthesized based on a ternary material, by adjusting the ratio of Ni, Co, and Mn elements, while selecting a high-nickel ternary precursor material. The elemental ratio of this precursor material allows it to be doped by the inducing material (such as Nb, Bi, Sb, Mo, etc.), resulting in a change in crystal structure and forming a pure spinel phase structure. This method overcomes the disadvantage of the difficulty in easily synthesizing pure spinel phase and similar materials. It is not only simple in process but also has undemanding reaction conditions and short processing time, possessing the potential for large-scale application. The preparation process of the present invention, whether for synthesizing the spinel phase structure or for coating, is compatible with conventional cathode material preparation methods. The resulting cathode material with a protective layer structure can protect cathode particles, improve cycle life, and effectively increase the thermal decomposition temperature of pure high-nickel ternary materials, reduce heat release, and improve safety performance.

[0021] In some embodiments of the present invention, the spinel phase material includes Na[(Ni a Co b Mn c ) d TM e O2, wherein 0.6≤a<1, 0<b≤0.2, 0<c≤0.2, a+b+c=1 and b=c; 0.8≤d<1, 0<e≤0.2, and d+e=1; TM is selected from at least one of Nb, Bi, Sb, and Mo. Because pure spinel phase and similar materials are difficult to synthesize simply, chemical element substitution has become a suitable method for developing high-performance spinel phase materials. This invention improves the cycle stability and safety of high-nickel ternary cathodes by coating them with layered spinel phase oxides.

[0022] In some preferred embodiments of the present invention, 0.8≤a<1, 0<b≤0.1, 0<c≤0.1, a+b+c=1 and b=c.

[0023] In some preferred embodiments of the present invention, the spinel material is Na[(Ni 0.8 Co 0.1 Mn 0.1 ) 0.9 TM 0.1 O2 and TM are selected from at least one of Nb, Bi, Sb, and Mo.

[0024] Specifically, the spinel material can be Na[(Ni 0.8 Co 0.1 Mn 0.1 ) 0.9 Nb 0.1 O2, Na[(Ni 0.8 Co 0.1 Mn 0.1 ) 0.9 Bi 0.1 O2, Na[(Ni 0.8 Co 0.1 Mn 0.1 ) 0.9 Sb 0.1 O2, Na[(Ni 0.8 Co 0.1 Mn 0.1 ) 0.9 Mo 0.1 One of the O2 components.

[0025] In some embodiments of the present invention, the sodium source includes sodium carbonate and sodium hydroxide. Preferably, the sodium source includes sodium carbonate.

[0026] In some embodiments of the present invention, the inducing material includes at least one of niobium-containing compounds, bismuth-containing compounds, antimony-containing compounds, and molybdenum-containing compounds.

[0027] In some preferred embodiments of the present invention, the niobium-containing compound includes H5Nb3O 10 At least one of Nb2O5.

[0028] In some preferred embodiments of the present invention, the bismuth-containing compound includes at least one of Bi(OH)3 and Bi2O3.

[0029] In some preferred embodiments of the present invention, the antimony-containing compound Sb2O3 is used.

[0030] In some preferred embodiments of the present invention, the molybdenum-containing compound MoCl5 is used.

[0031] In some embodiments of the present invention, the high-nickel ternary precursor material includes [Ni a Co b Mn c CO3 precursor material, wherein 0.6≤a<1, 0<b≤0.2, 0<c≤0.2, a+b+c=1 and b=c.

[0032] This invention selects a precursor material with a unique ratio of Ni, Co, and Mn by adjusting the elemental proportions of Ni. a Cob Mn c CO3, this precursor material, can be doped with the inducing material to undergo a change in crystal structure, forming a spinel phase, and finally a spinel phase material can be synthesized on the basis of high-nickel ternary material.

[0033] In some preferred embodiments of the present invention, 0.8≤a<1, 0<b≤0.1, 0<c≤0.1, a+b+c=1 and b=c.

[0034] Preferably, the high-nickel ternary precursor material is [Ni 0.8 Co 0.1 Mn 0.1 CO3. By adjusting the elemental ratio of Ni, Co, and Mn, the precursor material obtained with the above-mentioned special ratio is more easily induced to be doped, undergoing crystal structure changes and forming a spinel phase.

[0035] In some embodiments of the present invention, the [Ni] a Co b Mn c The particle size range of the CO3 precursor material is 5–15 μm, and other particle size ranges within this range are also possible, such as 5–10 μm or 10–15 μm.

[0036] In some embodiments of the present invention, the particle size range of the inducing material is 1 to 10 μm, and other particle size ranges within this range may also be used, such as 1 to 5 μm or 5 to 10 μm.

[0037] In some embodiments of the present invention, the [Ni] a Co b Mn c The CO3 precursor material was prepared by a co-precipitation process.

[0038] In some embodiments of the present invention, the molar ratio of the inducing material to the high-nickel ternary precursor material is 1:10 to 1:40. The present invention reasonably controls the ratio of the inducing material to the precursor. If the ratio is less than 1:40, it is impossible to induce the formation of a pure spinel phase structure, and if the ratio exceeds 1:10, excessive consumption of sodium source is also not conducive to the formation of a pure spinel phase structure.

[0039] Specifically, the inducing material and the [Ni a Co b Mn c The molar ratio of CO3 precursor materials is 1:10 to 1:40.

[0040] In some preferred embodiments of the present invention, the molar ratio of the inducing material to the high-nickel ternary precursor material is 1:25 to 1:40. More preferably, it is about 1:30.

[0041] In some embodiments of the present invention, the molar ratio of the sodium source to the high-nickel ternary precursor material is (1.1 - 3):1, preferably (1.1 - 1.5):1. To avoid the loss of the sodium source during the calcination process, the molar amount of the sodium source should be 5% - 10% in excess on this basis. For example, the molar ratio of the sodium source material to the [Ni a Co b Mn c CO3 precursor material can be 1.1:1.

[0042] In some embodiments of the present invention, the matrix material includes Na[Ni x Co y Mn z O2, where 0.6 ≤ x < 1, 0 < y ≤ 0.2, 0 < z ≤ 0.2, and x + y + z = 1.

[0043] In some preferred embodiments of the present invention, 0.8 ≤ x < 1, 0 < y ≤ 0.1, 0 < z ≤ 0.1, and x + y + z = 1.

[0044] Preferably, the matrix material is Na[Ni 0.8 Co 0.1 Mn 0.1 O2.

[0045] In some embodiments of the present invention, the mass proportion of the spinel phase material in the total mass of the matrix material and the spinel phase material is 0.5% - 10%.

[0046] In the present invention, the coating amount of the spinel phase material needs to be controlled within a reasonable range. This is because as the coating amount increases, the thermal stability of the cathode material will also increase significantly, but excessive coating will significantly reduce the energy density. The present invention finally controls the mass proportion of the spinel phase material in the total mass of the matrix material and the spinel phase material to be 0.5% - 10%. Within the above coating proportion range, the cathode material has better thermal stability and cycle stability, and at the same time has a higher energy density.

[0047] In some preferred embodiments of the present invention, the mass proportion of the spinel phase material in the total mass of the matrix material and the spinel phase material is 0.5% - 5%, for example, it can specifically be 0.5%, 1%, 5%.

[0048] In some embodiments of the present invention, in step S1, the rotational speed of the ball mill is 3000 r / min to 5000 r / min, preferably 3000 r / min to 4000 r / min, and more preferably about 3600 r / min.

[0049] In some embodiments of the present invention, in step S1, the ball milling time is 4h to 8h, preferably 4h to 6h, and more preferably about 5h.

[0050] In some embodiments of the present invention, in step S1, the temperature of the high-temperature sintering is 900°C to 1200°C, preferably 900°C to 1000°C, and more preferably about 900°C.

[0051] In some embodiments of the present invention, in step S1, the high-temperature sintering time is 12h to 24h, preferably 12h to 18h, and more preferably about 15h.

[0052] In some embodiments of the present invention, in step S2, the rotational speed of the ball mill is 3000 r / min to 5000 r / min, preferably 3000 r / min to 4000 r / min, and more preferably about 3600 r / min.

[0053] In some embodiments of the present invention, in step S2, the ball milling time is 4h to 8h, preferably 4h to 6h, and more preferably about 5h.

[0054] In some embodiments of the present invention, in step S2, the temperature of the secondary sintering is 300°C to 600°C, preferably 400°C to 500°C, and more preferably about 450°C.

[0055] In some embodiments of the present invention, in step S2, the secondary sintering time is 2h to 8h, preferably 6h to 8h, and more preferably about 6h.

[0056] This invention utilizes a sodium source and co-precipitated [Ni] a Co b Mn cCO3 precursor and inducing material are mixed in a molar ratio of 1:10 to 1:40. After rapid and uniform mixing via ball milling, the mixture is sintered at high temperature to obtain a spinel phase material. Subsequently, the matrix material and spinel phase material are mixed at a mass ratio of 0.5% to 10% of the total mass of the matrix material and spinel phase material. This mixture is then ball-milled at high speed and sintered to obtain the cathode material. This cathode material effectively protects the cathode matrix particles, improving cycle life. Simultaneously, it effectively increases the thermal decomposition temperature of pure high-nickel ternary materials, reduces heat release, and improves safety performance. Furthermore, the synthesis of this spinel phase coating material is simple, and the electrochemical performance of the coated cathode material under high voltage is improved.

[0057] In a third aspect, the present invention provides a positive electrode sheet comprising a positive current collector and a positive active material layer coated on at least one surface of the positive current collector, wherein the positive active material layer comprises a positive electrode material as described above or a positive electrode material prepared by the preparation method described above.

[0058] The positive electrode sheet according to the embodiments of the present invention has at least the following beneficial effects: The positive electrode sheet proposed in the present invention uses the above-mentioned positive electrode material with a protective layer structure. This material is composed of a spinel phase material coated with a high-nickel ternary material, which can protect the positive electrode particles, improve cycle life, and effectively increase the thermal decomposition temperature of the pure high-nickel ternary material, reduce heat release, improve safety performance, and ultimately improve the electrochemical performance of the positive electrode sheet under high voltage.

[0059] In some embodiments of the present invention, the positive current collector is a commonly used positive current collector in the art, such as aluminum foil, but is not limited thereto. The conductive agents, binders, etc., used in preparing the positive electrode sheet are all conventional materials in the art, and will not be described in detail here.

[0060] In a fourth aspect, the present invention provides a sodium-ion battery comprising a positive electrode, a negative electrode, and a separator spaced between the positive electrode and the negative electrode as described above.

[0061] The sodium-ion battery according to the embodiments of the present invention has at least the following beneficial effects: The battery proposed by the present invention uses a positive electrode sheet prepared by the above-mentioned positive electrode material, and therefore it has at least all the beneficial effects brought about by the technical solution of the above-mentioned embodiments, that is, the resulting battery is more stable, has better electrochemical performance, higher specific capacity, and better cycle capacity retention.

[0062] In some embodiments of the present invention, the negative electrode active material of the negative electrode sheet of the sodium-ion battery includes at least one of carbon materials, sulfides, oxides, elemental metals, and alloy materials.

[0063] In some embodiments of the present invention, the negative electrode active material of the negative electrode sheet of the sodium-ion battery is a hard carbon-based material.

[0064] In some embodiments of the present invention, the positive electrode sheet provided by the present invention can also be used in energy storage devices such as supercapacitors and hybrid supercapacitors. There are no limitations on the negative electrode, separator, electrolyte, etc., used in assembling the battery; commonly used materials in the art can be reasonably employed, and will not be elaborated further here.

[0065] In a fifth aspect, the present invention provides the application of the above-described cathode material or the cathode material prepared by the above-described preparation method in the preparation of energy storage devices, electrical devices or electronic devices. Attached Figure Description

[0066] The present invention will be further described below with reference to the accompanying drawings and embodiments, wherein:

[0067] Figure 1 This is a schematic diagram of the XRD test results of the positive electrode sheet prepared in Example 2 of the present invention. Detailed Implementation

[0068] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0069] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0070] In the description of this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are both real numbers. Unless otherwise stated, the various reaction or operation steps may be performed sequentially or not. Preferably, the reaction methods in this invention are performed sequentially.

[0071] Unless otherwise specified in the following examples, the techniques or conditions described in the literature in this field or in accordance with the product instructions shall apply. All reagents or instruments without a specified manufacturer are commercially available conventional products.

[0072] Example 1

[0073] 1. Preparation of cathode materials

[0074] (1) First, sodium carbonate (sodium source) and [Ni] obtained by co-precipitation are used. 0.8 Co 0.1 Mn 0.1 CO3 precursor and inducing material Nb2O5 were mixed in a molar ratio, controlling the molar ratio of sodium source to precursor to be 1:1 (to avoid sodium source loss during calcination, the molar amount of sodium source can be in excess by 5%), and the molar ratio of inducing material to precursor to be 1:10. The mixture was then ball-milled uniformly at 3600 r / min for 5 h; followed by high-temperature sintering at 900℃ for 15 h. After natural cooling, a spinel phase coated material Na[(Ni)] was obtained. 0.8 Co 0.1 Mn 0.1 ) 0.7 Nb 0.3 O2.

[0075] (2) The spinel phase coating material obtained in step (1) is combined with the matrix material Na[Ni 0.8 Co 0.1 Mn 0.1 O2 was mixed, and the mass ratio of the spinel phase material to the total mass of the matrix material and the spinel phase material was controlled to be 0.5%. The above mixture was then ball-milled at high speed at a speed of 3600 r / min for 5 h; then sintered at 450℃ for 6 h, and naturally cooled to obtain the cathode material.

[0076] 2. Preparation of the positive electrode sheet

[0077] The positive electrode material, conductive agent acetylene black, and binder polyvinylidene fluoride (PVDF) prepared above were thoroughly mixed in an N-methylpyrrolidone solvent system at a mass ratio of 8:1:1. The mixture was then coated onto the positive electrode current collector Al foil, dried under vacuum at 80°C, and cut into sheets to obtain the positive electrode sheet.

[0078] 3. Preparation of electrolyte

[0079] Inside the glove box, sodium-ion battery electrolyte was prepared with NaPF6 as the sodium salt and 5% by mass of fluoroethylene carbonate (FEC) as the electrolyte solvent, added at a volume ratio of 1:1 (EC:PC). The electrolyte was prepared at a concentration of 1 mol / L and set aside for later use.

[0080] 4. Preparation of sodium-ion button cells

[0081] A positive electrode sheet (area density ~2.5 mg / cm³) is used. 2 Sodium metal is used as the positive electrode, sodium metal as the negative electrode, and PE membrane is used to assemble a 2032 type layered oxide button cell. The button cell assembly order from bottom to top is: negative electrode shell, spring, stainless steel gasket, sodium sheet, electrolyte, PE membrane, electrolyte, positive electrode material, and positive electrode shell.

[0082] Example 2

[0083] The preparation method is the same as in Example 1, except that the molar ratio of the inducing material to the precursor is 1:30 in Example 2.

[0084] Example 3

[0085] The preparation method is the same as in Example 1, except that the molar ratio of the inducing material to the precursor in Example 3 is 1:40.

[0086] Example 4

[0087] The preparation method is the same as in Example 1, except that in Example 4, the mass ratio of the spinel phase material to the total mass of the matrix material and the spinel phase material is 1%.

[0088] Example 5

[0089] The preparation method is the same as in Example 1, except that in Example 5 the molar ratio of the inducing material to the precursor is 1:30; and the mass ratio of the spinel phase material to the total mass of the matrix material and the spinel phase material is 1%.

[0090] Example 6

[0091] The preparation method is the same as in Example 1, except that in Example 6 the molar ratio of the inducing material to the precursor is 1:40; and the mass of the spinel phase material accounts for 1% of the total mass of the matrix material and the spinel phase material.

[0092] Example 7

[0093] The preparation method is the same as in Example 1, except that in Example 7, the mass of the spinel phase material accounts for 5% of the total mass of the matrix material and the spinel phase material.

[0094] Example 8

[0095] The preparation method is the same as in Example 1, except that the molar ratio of the inducing material to the precursor is 1:30 in Example 8; and the mass of the spinel phase material accounts for 5% of the total mass of the matrix material and the spinel phase material.

[0096] Example 9

[0097] The preparation method is the same as in Example 1, except that in Example 9 the molar ratio of the inducing material to the precursor is 1:40; and the mass of the spinel phase material accounts for 5% of the total mass of the matrix material and the spinel phase material.

[0098] Comparative Example 1

[0099] The preparation method is the same as in Example 1, except that the molar ratio of the inducing material to the precursor in Comparative Example 1 is 1:8.

[0100] Comparative Example 2

[0101] The preparation method is the same as in Example 1, except that the molar ratio of the inducing material to the precursor in Comparative Example 2 is 1:50.

[0102] Comparative Example 3

[0103] The preparation method is the same as in Example 1, except that in Comparative Example 3, the mass ratio of spinel phase material to the total mass of matrix material and spinel phase material is 15%.

[0104] The molar ratio of the inducing material to the precursor, the mass ratio of the coating material to the cathode material, and the structure of the coating material in Examples 1-9 and Comparative Examples 1-3 are shown in Table 1.

[0105] Performance testing

[0106] (1) XRD test

[0107] The positive electrode sheets prepared in the comparative and examples were subjected to X-ray diffraction (XRD) tests. X-ray diffraction (XRD) is mainly used to study the internal crystal structure of materials because X-rays have wavelengths close to the interplanar spacing and have a certain penetrating power. A beam of X-rays passes through a crystal and diffracts; by analyzing the diffraction pattern, phase identification and structural analysis can be performed. Test conditions: Cu Kα radiation, operating current 250 mA, continuous scanning, operating voltage 40 kV, scanning range 2θ 10–80°, scanning speed 2°·min⁻¹.

[0108] The XRD test results of Example 2 are as follows: Figure 1 As shown in the figure, the upper figure shows the matrix material Na[Ni]. 0.8 Co 0.1 Mn 0.1 The XRD pattern and PDF card of O2 show that the matrix material obtained by the co-precipitation method is a pure O3 phase, corresponding to standard card PDF#54-0887, space group R-3m; the figure below shows the spinel phase coated material Na[(Ni 0.8 Co0.1 Mn 0.1 ) 0.9 Nb 0.1 The XRD pattern and PDF card of O2 show that the coating material is a pure spinel phase, corresponding to standard card PDF#73-1523, space group Fm-3m. This demonstrates the feasibility of the synthesis method in this embodiment, showing that a pure spinel phase material can be formed by doping a high-valence transition metal element into a high-nickel ternary matrix.

[0109] (2) Gram capacity test

[0110] Five sodium-ion coin cells from the comparative example and the embodiment were taken and charged at a constant current rate of 0.1C at room temperature until the voltage reached 4.5V. They were then further charged at a constant voltage of 4.5V until the current dropped below 0.05C, bringing them to a fully charged state of 4.5V. Subsequently, they were discharged at a constant current rate of 0.1C until the voltage reached 2.0V.

[0111] (3) Cyclic performance test

[0112] Five sodium-ion coin cells were taken from each of the comparative and example samples. The sodium-ion coin cells were repeatedly charged and discharged through the following steps, and the cycle capacity retention rate was calculated.

[0113] First, in an environment of 25℃, the first charge and discharge cycle was performed. Constant current and constant voltage charging was carried out at a charging current of 1C (i.e., the current value that completely discharges the theoretical capacity within 1 hour) until the upper limit voltage is 4.5V. Then, constant current discharge was carried out at a discharge current of 1C until the final voltage is 2V. The discharge capacity of the first cycle was recorded. Then, 100 charge and discharge cycles were performed, and the discharge capacity of the 100th cycle was recorded.

[0114] Cycle capacity retention = (Discharge capacity of the 100th cycle / Discharge capacity of the first cycle) × 100%.

[0115] Table 1 shows the specific capacity test and cycle performance test data for Examples 1-9 and Comparative Examples 1-3:

[0116] Table 1

[0117]

[0118] Comparison of the comparative and exemplary examples shows that coating high-nickel ternary materials with spinel phase materials can effectively improve the capacity density and cycle stability of the cathode material. Specifically, firstly, by controlling the ratio of the inducing material to the precursor within a reasonable range, a pure spinel phase structure can be achieved. A ratio less than 1:40 cannot induce the formation of a pure spinel phase structure, while a ratio exceeding 1:10 leads to excessive consumption of the sodium source, which is also detrimental to the formation of a pure spinel phase structure. Failure to form a pure spinel phase structure will simultaneously reduce both specific capacity and cycle stability. Secondly, the amount of spinel coating also needs to be controlled. As the mass of the coating material increases, the thermal stability of the cathode material improves significantly, but excessive coating will significantly reduce the energy density. A coating material ratio exceeding 5% will also simultaneously reduce both specific capacity and cycle stability. By reasonably controlling the ratio of the inducing material to the precursor and the amount of material coating during the synthesis process, both the specific capacity and cycle stability of the cathode material can be improved.

[0119] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A positive electrode material, characterized in that, It includes a matrix material and a spinel phase material, wherein the spinel phase material is coated on at least a portion of the surface of the matrix material; The spinel phase material includes Na[(Ni)] a Co b Mn c ) d TM e O2, wherein 0.6≤a<1, 0<b≤0.2, 0<c≤0.2, a+b+c=1 and b=c; 0.8≤d<1, 0<e≤0.2 and d+e=1; TM is selected from at least one of Nb, Bi, Sb, and Mo; The matrix material includes Na[Ni x Co y Mn z O2, where 0.6 ≤ x < 1, 0 < y ≤ 0.2, 0 < z ≤ 0.2, and x + y + z = 1.

2. The cathode material according to claim 1, characterized in that, The spinel phase material accounts for 0.5% to 10% of the mass of the cathode material.

3. The cathode material according to claim 2, characterized in that, The spinel phase material accounts for 0.5% to 5% of the mass of the cathode material.

4. A method for preparing a positive electrode material as described in any one of claims 1-3, characterized in that, Includes the following steps: Sodium source, inducing material and high-nickel ternary precursor material are provided, and after being ball-milled and mixed evenly, spinel phase material is obtained by high-temperature sintering. The spinel phase material and the matrix material are mixed evenly by ball milling, and then sintered twice to obtain the cathode material.

5. The method for preparing the cathode material according to claim 4, characterized in that, The inducing material includes at least one of the following: niobium-containing compounds, bismuth-containing compounds, antimony-containing compounds, and molybdenum-containing compounds.

6. The method for preparing the cathode material according to claim 5, characterized in that, The niobium-containing compound includes H5Nb3O 10 At least one of Nb2O5.

7. The method for preparing the cathode material according to claim 5, characterized in that, The bismuth-containing compound includes at least one of Bi(OH)3 and Bi2O3.

8. The method for preparing the cathode material according to claim 5, characterized in that, The antimony-containing compound Sb₂O₃.

9. The method for preparing the cathode material according to claim 5, characterized in that, The molybdenum-containing compound MoCl5.

10. The method for preparing the cathode material according to claim 5, characterized in that, The high-nickel ternary precursor material includes [Ni] a Co b Mn c CO3 precursor material, wherein 0.6≤a<1, 0<b≤0.2, 0<c≤0.2, a+b+c=1 and b=c.

11. The method for preparing the cathode material according to claim 5, characterized in that, The sodium source includes sodium carbonate and sodium hydroxide.

12. The method for preparing the cathode material according to claim 10, characterized in that, The [Ni a Co b Mn c The particle size range of CO3 precursor materials is 5~15μm.

13. The method for preparing the cathode material according to claim 5, characterized in that, The particle size range of the inducing material is 1~10μm.

14. The method for preparing the cathode material according to claim 4, characterized in that, The molar ratio of the inducing material to the high-nickel ternary precursor material is 1:10 to 1:

40.

15. The method for preparing the cathode material according to claim 14, characterized in that, The molar ratio of the inducing material to the high-nickel ternary precursor material is 1:25 to 1:

40.

16. The method for preparing the cathode material according to claim 14, characterized in that, The molar ratio of the sodium source to the high-nickel ternary precursor material is (1.1~3):

1.

17. The method for preparing the cathode material according to claim 16, characterized in that, The molar ratio of the sodium source to the high-nickel ternary precursor material is (1.1~1.5):

1.

18. The method for preparing the cathode material according to claim 4, characterized in that, The ball mill rotates at a speed of 3000 r / min to 5000 r / min.

19. The method for preparing the cathode material according to claim 18, characterized in that, The ball mill rotates at a speed of 3000 r / min to 4000 r / min.

20. The method for preparing the cathode material according to claim 18, characterized in that, The ball milling time is 4 to 8 hours.

21. The method for preparing the cathode material according to claim 20, characterized in that, The ball milling time is 4 to 6 hours.

22. The method for preparing the cathode material according to claim 18, characterized in that, The high-temperature sintering temperature is 900℃~1200℃.

23. The method for preparing the cathode material according to claim 22, characterized in that, The high-temperature sintering temperature is 900℃~1000℃.

24. The method for preparing the cathode material according to claim 18, characterized in that, The high-temperature sintering time is 12h~24h.

25. The method for preparing the cathode material according to claim 24, characterized in that, The high-temperature sintering time is 12h~18h.

26. The method for preparing the cathode material according to claim 18, characterized in that, The temperature for the secondary sintering is 300℃~600℃.

27. The method for preparing the cathode material according to claim 26, characterized in that, The temperature for the secondary sintering is 400℃~500℃.

28. The method for preparing the cathode material according to claim 18, characterized in that, The secondary sintering time is 2h to 8h.

29. The method for preparing the cathode material according to claim 28, characterized in that, The secondary sintering temperature is 6h~8h.

30. A positive electrode sheet, comprising a positive current collector and a positive active material layer coated on at least one surface of the positive current collector, characterized in that, The positive electrode active material layer comprises the positive electrode material as described in any one of claims 1-3 or the positive electrode material prepared by the preparation method described in any one of claims 4-29.

31. A sodium-ion battery, comprising a positive electrode, a negative electrode, and a separator spaced between the positive electrode and the negative electrode, characterized in that, The positive electrode is as described in claim 30.

32. The use of a cathode material as described in any one of claims 1-3 or a cathode material prepared by the preparation method described in any one of claims 4-29 in the preparation of energy storage devices, electrical devices or electronic devices.

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