Medium-entropy manganese-based phosphate sodium battery positive electrode material as well as preparation method and application thereof

Abstract

The invention provides a medium-entropy manganese-based phosphate sodium battery positive electrode material as well as a preparation method and application thereof, and belongs to the field of sodium ion battery positive electrode materials. The chemical formula of the medium-entropy manganese-based phosphate sodium battery positive electrode material is Na < x > (Mn < M >) < y > (PO4) < 3, 2lt >, x is less than or equal to 5, 0lt; y is less than or equal to 1, and M is at least two of Ti, V, Fe, Cr, Al, Sc, Mg, Nb, Ni, Co, Mo, Zr, Cu and Ga. The preparation method comprises the following steps: mixing a sodium source, a manganese salt, a phosphorus source, a transition metal salt and a carbon source according to a certain ratio (the configuration entropy value is between R and 1.5 R, and R represents an ideal gas constant), adding a proper amount of a solvent, carrying out ball milling to obtain a uniformly mixed precursor slurry, drying and pulverizing the slurry, and finally, carrying out sintering treatment in an inert gas atmosphere to obtain the manganese-manganese-carbon composite material. The medium-entropy manganese-based phosphate positive electrode material is obtained. By regulating and controlling the configuration entropy value, the local structure of the manganese-based phosphate positive electrode material can be precisely regulated and controlled, the electrical property of the material is optimized, and the method has a great commercial application prospect.

Description

Technical Field

[0001] The present invention relates to a sodium ion battery positive electrode material, in particular to a medium entropy manganese-based phosphate Na x (MnM) y (PO4)3 sodium positive electrode material and preparation method thereof, and Na x (MnM) y The application of (PO4)3 as a sodium ion positive electrode material belongs to the field of sodium ion batteries. Background Art

[0002] With the global emphasis on sustainable development, the demand for energy storage systems continues to grow, promoting the rapid progress of sodium-ion battery technology. Sodium-ion batteries have become an effective supplement to lithium-ion batteries due to their abundant resources and low cost. In terms of the positive electrode of sodium-ion batteries, polyanion phosphates with a sodium superionic conductor (NASICON) structure show good application prospects due to their stable framework and excellent ion diffusion properties. However, NASICON materials still have deficiencies in specific capacity and electronic conductivity, which seriously restricts their commercialization process. In response to the above problems, researchers have regulated the local chemical bonds and electron distribution of materials by means of composite conductive additives, optimizing material redox centers, and optimizing material particle size, significantly improving the specific capacity and electronic conductivity of the materials and achieving improved electrochemical performance of the materials.

[0003] In recent years, related research has mainly focused on single or double transition metal NASICON phosphate systems. Among them, the research on manganese-based phosphate cathode materials has made some progress due to the safety and non-toxicity of manganese, high redox potential, and relatively low price. However, there is still a lack of systematic research on multiple transition metals, such as Mn 3+ Issues such as strategies to suppress the Chiang-Taylor effect remain unresolved.

[0004] In view of this, it is necessary to design a medium-entropy manganese-based sodium phosphate cathode material and a preparation method thereof to solve the above problems. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention aims to provide a medium-entropy manganese-based phosphate Na x (MnM) y (PO4)3 positive electrode material, which has a sodium superion conductor (NASICON) structure and a configuration entropy value between R and 1.5R (R represents the gas constant).

[0006] The medium entropy manganese-based phosphate Na x (MnM) y The preparation method of (PO4)3 positive electrode material has mild reaction conditions, simple operation, low cost, and can be used for large-scale production.

[0007] In a first aspect, the present invention provides a sodium manganese-based phosphate cathode material for an electric battery. The sodium manganese-based phosphate cathode material for an electric battery has a NASICON-type structure and its chemical formula is Na x (MnM) y (PO4)3, where 2 < x ≤ 5, 0 < y ≤ 1, and M is at least two of Ti, V, Fe, Cr, Al, Sc, Mg, Nb, Ni, Co, Mo, Zr, Cu, and Ga.

[0008] Furthermore, the powder particle size of the sodium manganese-based phosphate cathode material for an electric battery is distributed between 100 nm and 10 μm.

[0009] In a second aspect, the present invention provides a method for preparing a sodium manganese-based phosphate cathode material for an electric battery, comprising the following steps:

[0010] S1, mixing a sodium source, a manganese source, a phosphorus source, a carbon source, and a transition metal source in a predetermined ratio to obtain a mixed material; the predetermined ratio is determined according to the calculation formula of configurational entropy value; the configurational entropy value is between R and 1.5R, where R represents the ideal gas constant;

[0011] The calculation formula of the configurational entropy value is as follows: ΔS conf =-R∑ n i＝1 x i lnx i ; where R is the ideal gas constant, x i represents the molar fraction of the i-th component, and n represents the number of elements;

[0012] S2, performing ball milling on the mixed material obtained in step S1 to obtain a uniform precursor slurry;

[0013] S3, after drying and pulverizing the precursor slurry obtained in step S2, performing sintering treatment in an inert gas atmosphere to obtain the sodium manganese-based phosphate cathode material for an electric battery.

[0014] Furthermore, the sodium source is one or more of sodium acetate, sodium oxalate, sodium citrate, sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium dihydrogen phosphate, and disodium hydrogen phosphate;

[0015] The manganese source is one or more of manganese acetate, manganese oxalate, manganese carbonate, and manganese acetylacetonate;

[0016] The phosphorus source is one or more of ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, and phosphoric acid;

[0017] The carbon source is one or more of citric acid, acetic acid, glucose, sucrose, ascorbic acid, malic acid, polyvinylidene fluoride, polyvinyl pyrrolidone, polystyrene, polyacrylonitrile powder, polyethylene terephthalate, polymethyl methacrylate, polyurethane, polylactic acid, graphene, carbon nanotubes and polyvinyl alcohol;

[0018] The transition metal source includes at least two of a titanium source, a vanadium source, an iron source, a chromium source, an aluminum source, a scandium source, a magnesium source, a niobium source, a nickel source, a cobalt source, a molybdenum source, a zirconium source, a copper source, and a gallium source.

[0019] Further, the titanium source is a mixture of one or more of di(2-hydroxypropionic acid) diammonium dihydroxide titanium, tetrabutyl titanate, isopropyl titanate, tetraethyl titanate, titanium acetylacetonate and titanium dioxide;

[0020] The vanadium source is one or more mixtures of ammonium metavanadate, vanadium oxide, vanadium pentoxide, vanadyl oxalate, vanadyl acetylacetonate and vanadium acetylacetonate;

[0021] The iron source is a mixture of one or more of ferric acetate and its hydrate, ferrous oxalate and its hydrate, ferrous citrate, iron oxide, ferric nitrate and its hydrate;

[0022] The chromium source is one or more mixtures of chromium acetate, chromium acetate hydroxide and chromium oxide;

[0023] The aluminum source is a mixture of one or more of aluminum carbonate, aluminum oxalate, and aluminum oxide;

[0024] The scandium source is one or more mixtures of scandium oxide, scandium oxalate, scandium acetate, scandium acetylacetonate and hydrates thereof;

[0025] The magnesium source is one or more mixtures of magnesium acetate, magnesium carbonate and magnesium oxide;

[0026] The niobium source is one or more of niobium oxide, niobium hydroxide, sodium niobate, ethoxy niobium, hydrated niobium oxalate, and ammonium niobate oxalate hydrate;

[0027] The nickel source is one or more of nickel hydroxide, nickel oxide, nickel acetylacetonate, nickel hydroxyacetate, nickel oxide, nickel peroxide, nickel hypophosphite, nickel oxalate, nickel acetate and a mixture thereof;

[0028] The cobalt source is a mixture of one or more of cobalt oxide, cobalt carbonate and cobalt acetate;

[0029] The molybdenum source is one or more mixtures of molybdenum acetylacetonate, molybdenum hexacarbonyl, sodium molybdate dihydrate, molybdenum acetate dimer, molybdenum isopropoxide, ammonium molybdate and hydrates thereof;

[0030] The zirconium source is one or more mixtures of zirconium acetate, zirconium acetylacetonate, zirconium propionate, ammonium zirconium carbonate, carboxyethyl zirconium acrylate, zirconyl hydroxide, zirconium dioxide, and zirconium hydroxide;

[0031] The copper source is one or more mixtures of copper citrate, copper acetylacetonate, basic copper carbonate, copper oxalate, copper acetate, copper acetylacetate, copper tartrate hydrate, copper gluconate, copper oxide, copper carbonate and hydrates thereof;

[0032] The gallium source is one or more mixtures of gallium oxide, gallium acetate, gallium nitrate and hydrates thereof.

[0033] Furthermore, in step S2, the ball milling treatment is carried out in a solvent medium such as water, isopropanol, acetone, etc. that does not react with the material.

[0034] Furthermore, in step S2, during the ball milling process, the mass ratio of zirconium beads to the material is (30-120):1; the main machine speed is 200-400 r / min, and the ball milling time is 0.5-24 h.

[0035] Furthermore, in step S3, the drying and pulverizing process is as follows: the precursor slurry is placed under a temperature of 80 to 100° C. for forced drying, pulverized by a jet mill, and then sieved through a 100 to 400 mesh sieve to obtain the powder under the sieve.

[0036] Furthermore, in step S3, the sieved powder is placed in a rapid reaction furnace, a tubular furnace or a rotary kiln and sintered in an inert gas atmosphere; when a rapid reaction furnace is used for sintering, the sintering temperature is 700-1000°C and the sintering time is 10-60s; when a tubular furnace is used for sintering, the temperature is increased to 600-800°C at a heating rate of (2-10)°C / min, and the sintering time is 6-48h; when a rotary kiln is used for sintering, the rotation speed is (1-5)r / min, the temperature is increased to 600-750°C at a heating rate of (2-10)°C / min, and the sintering time is 6-24h.

[0037] Furthermore, the inert gas is one of argon, nitrogen, carbon monoxide, argon-hydrogen mixed gas and nitrogen-hydrogen mixed gas.

[0038] In the third aspect, the medium-entropy manganese-based phosphate Na prepared by the above scheme x (MnM) y (PO4)3 material can be used as the positive electrode material of sodium ion batteries. The prepared sodium ion batteries exhibit high specific capacity, high operating voltage, good cycle stability and excellent rate performance.

[0039] Specifically, the obtained medium entropy manganese-based phosphate Na x (MnM) y(PO4)3 material powder, conductive agent and binder are dissolved in a certain amount of solvent according to mass percentage, mixed and evenly coated on the current collector to prepare the battery pole piece. The mass percentage of each component is: 60% to 80% of medium entropy manganese-based phosphate powder, 10% to 20% of conductive additive, and 10% to 15% of binder, wherein the sum of the mass percentages of medium entropy manganese-based phosphate powder, conductive additive and binder is 100%. Sodium metal sheet is used as the negative electrode of the half-cell, and the battery electrochemical performance test is carried out at a battery voltage of 1.5 to 4.4V.

[0040] Preferably, the conductive additive is one of graphene, carbon nanotubes, acetylene black, Super P, Ketjen black or a mixture of several thereof; the binder is one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC), and sodium alginate; the solvent is one of N-methyl-2-pyrrolidone, N,N-dimethylaminopropylamine, and diethyltriamine; the current collector is one of aluminum foil, carbon-coated aluminum foil, and copper foil.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] (1) The medium-entropy manganese-based sodium phosphate cathode material provided by the present invention accurately designs the local structure of the material by regulating the configurational entropy, efficiently controls the material distortion, and optimizes the manganese-based phosphate cathode material with a NASICON structure.

[0043] (2) The preparation method provided by the present invention has a simple synthesis process, cheap and readily available raw materials, and a high yield. Among them, the required medium-entropy manganese-based sodium phosphate cathode material can be obtained in 10 to 60 seconds by using a rapid furnace, which is conducive to small-batch sample preparation research; kilogram-level medium-entropy manganese-based sodium phosphate cathode material can be prepared by using a rotary kiln, which is suitable for large-scale industrial production.

[0044] (3) The medium-entropy manganese-based sodium phosphate cathode material provided by the present invention is applied to the cathode material of sodium ion batteries, and the assembled sodium ion batteries exhibit high specific capacity, high operating voltage, good cycle stability and excellent rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is the SEM image of the medium-entropy manganese-based sodium phosphate cathode material prepared in Example 1.

[0046] Figure 2 This is the XRD diagram of the medium-entropy manganese-based sodium phosphate cathode material prepared in Example 1.

[0047] Figure 3 This is a cyclic voltammetry curve of the medium-entropy manganese-based sodium phosphate cathode material prepared in Example 1.

[0048] Figure 4 This is a charge and discharge curve diagram of the medium-entropy manganese-based sodium phosphate cathode material prepared in Example 1.

[0049] Figure 5 This is the cycle curve of the medium-entropy manganese-based sodium phosphate cathode material prepared in Example 1. DETAILED DESCRIPTION

[0050] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0052] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0053] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0054] In the description of the embodiments of the present application, the term "and / or" is only a description of the association relationship of the associated objects, indicating that there may be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0055] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0056] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installation", "connection", "connection", "fixation", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can also be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present application can be understood according to specific situations.

[0057] The configurational entropy value divides materials into three categories: low entropy (<1R, where R represents the ideal gas constant), medium entropy (1R - 1.5R), and high entropy (>1.5R). It is feasible to optimize the material properties by adjusting the configurational entropy value. For the manganese-based phosphate system, the composition of transition metals usually determines the redox potential, electron transfer number, and cycle stability of the material, and thus determines the energy density and service life of the battery. Now, the concept of "medium entropy" is introduced into material design to enhance the stability of the material (compared with low entropy) while avoiding excessive lattice distortion (compared with high entropy). By reasonably combining multiple transition metals, regulating the composition and ratio of the material, and designing the local structure of the material, more electron transfer, higher discharge specific capacity, and efficient control of material distortion can be achieved, and the cycle life can be extended. In addition, the manganese-based phosphate cathode material based on medium entropy regulation expands the range of selectable transition metals, and it is easy to obtain high-performance cathode materials with different properties, and the application range is wider.

[0058] In a first aspect, an embodiment of the present application provides a sodium-ion battery cathode material of medium-entropy manganese-based phosphate, which has a NASICON-type structure and its chemical formula is Na x (MnM) y (PO4)3, where 2 < x ≤ 5, 0 < y ≤ 1, and M is at least two of Ti, V, Fe, Cr, Al, Sc, Mg, Nb, Ni, Co, Mo, Zr, Cu, Ga.

[0059] The particle size distribution of the powder of the sodium-ion battery cathode material of medium-entropy manganese-based phosphate is between 100 nm and 10 μm.

[0060] In a second aspect, an embodiment of the present application provides a preparation method of a sodium-ion battery cathode material of medium-entropy manganese-based phosphate, including the following steps:

[0061] S1, mixing a sodium source, a manganese source, a phosphorus source, a carbon source, and a transition metal source according to a predetermined ratio to obtain a mixed material; where the predetermined ratio is determined according to the calculation formula of the configurational entropy value; the configurational entropy value is between R and 1.5R, where R represents the ideal gas constant;

[0062] The calculation formula of configuration entropy is as follows: ΔS conf =-R∑ n i＝1 x i lnx i ; where R is the ideal gas constant, x i represents the mole fraction of the i-th component, and n represents the number of elements;

[0063] S2, ball milling the mixed material obtained in step S1 to obtain a uniform precursor slurry;

[0064] The ball milling process is carried out in a solvent medium that does not react with the material, such as water, isopropanol, acetone, etc. Specifically, the solvent medium can be selected according to the material.

[0065] During ball milling, the mass ratio of zirconium beads to materials is (30-120):1; the main engine speed is 200-400 r / min, and the ball milling time is 0.5-24 h.

[0066] S3, drying and pulverizing the precursor slurry obtained in step S2, and then sintering it in an inert gas atmosphere to obtain a medium-entropy manganese-based sodium phosphate cathode material.

[0067] Specifically, the process of drying and pulverizing is as follows: the precursor slurry is placed under a temperature of 80 to 100° C. for air drying, pulverized by a jet mill, and then passed through a 100 to 400 mesh sieve to obtain the powder under the sieve.

[0068] Then, the sieved powder is placed in a fast reaction furnace, a tubular furnace or a rotary kiln for sintering under an inert gas atmosphere.

[0069] The inert gas is one of argon, nitrogen, carbon monoxide, argon-hydrogen mixed gas and nitrogen-hydrogen mixed gas.

[0070] Specifically, when conducting small batch sample preparation research, a rapid reaction furnace is used for sintering, and the sintering temperature is 700-1000° C. and the time is 10-60 seconds.

[0071] When a tubular furnace is used for sintering, the temperature is raised to 600-800°C at a heating rate of (2-10)°C / min, and the sintering time is 6-48h.

[0072] When preparing kilogram-level medium-entropy manganese-based sodium phosphate cathode material, a rotary kiln is used for sintering, the rotation speed is (1-5) r / min, the temperature is increased to 600-750°C at a heating rate of (2-10)°C / min, and the sintering time is 6-24h, which is suitable for large-scale industrial production.

[0073] In the third aspect, the medium entropy manganese-based phosphate Na prepared by the above scheme x (MnM)y (PO4)3 material can be used as the positive electrode material of sodium ion batteries. The prepared sodium ion batteries exhibit high specific capacity, high operating voltage, good cycle stability and excellent rate performance.

[0074] Specifically, the obtained medium entropy manganese-based phosphate Na x (MnM) y (PO4)3 material powder, conductive agent and binder are dissolved in a certain amount of solvent according to mass percentage, mixed and evenly coated on the current collector to prepare the battery pole piece. The mass percentage of each component is: 60% to 80% of medium entropy manganese-based phosphate powder, 10% to 20% of conductive additive, and 10% to 15% of binder, wherein the sum of the mass percentages of medium entropy manganese-based phosphate powder, conductive additive and binder is 100%. Sodium metal sheet is used as the negative electrode of the half-cell, and the battery electrochemical performance test is carried out at a battery voltage of 1.5 to 4.4V.

[0075] Preferably, the conductive additive is one or a mixture of graphene, carbon nanotubes, acetylene black, Super P, and Ketjen black; the binder is one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), sodium carboxymethyl cellulose (CMC), and sodium alginate; the solvent is one of N-methyl-2-pyrrolidone, N,N-dimethylaminopropylamine, and diethyltriamine; and the current collector is one of aluminum foil, carbon-coated aluminum foil, and copper foil.

[0076] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used without specifying the manufacturer are all conventional products that can be obtained commercially.

[0077] Example 1

[0078] This embodiment provides a medium entropy manganese-based sodium phosphate cathode material, whose chemical formula is Na3(MnVTi): 2 / 3 (PO4)3, the preparation method of the positive electrode material is:

[0079] 30 mmol of citric acid monohydrate, 4 mmol of manganese acetate tetrahydrate, 4 mmol of ammonium metavanadate, 18 mmol of sodium dihydrogen phosphate dihydrate and 4 mmol of di(2-hydroxypropionic acid)diammonium dihydroxide titanium were weighed and mixed according to the stoichiometric ratio; the mixture was then placed in a ball mill, followed by adding 5 mL of deionized water and 20 g of zirconium beads, and the ball mill was placed in a ball mill and milled at 300 r / min for 0.5 h.

[0080] Subsequently, the ball-milled precursor slurry was taken out and placed in a 90°C forced air oven for drying for 48 hours, and then ground and crushed through a 100-mesh sieve to obtain a precursor powder. The precursor powder was placed in a tube furnace, heated to 700°C at 3°C / min in an argon atmosphere, and sintered for 6 hours to finally obtain a chemical formula of Na3(MnVTi) 2 / 3 (PO4)3 medium-entropy manganese-based phosphate sodium-ion battery positive electrode material powder.

[0081] Figure 1 This is a SEM image of the medium-entropy manganese-based sodium phosphate cathode material prepared in Example 1. It can be seen that the medium-entropy manganese-based phosphate powder prepared in this example is granular, has good dispersibility, and has a size distribution of 100nm to 2μm.

[0082] Figure 2 This is the XRD diagram of the medium-entropy manganese-based sodium phosphate cathode material prepared in this example. Through XRD test analysis, it can be seen that the medium-entropy manganese-based phosphate prepared in this example belongs to the R-3c space group and has obvious NASICON structural characteristic peaks, indicating that the medium-entropy manganese-based phosphate has high crystallinity.

[0083] The medium entropy manganese-based phosphate Na3 (MnVTi) prepared in this example 2 / 3 (PO4)3 was used as the positive electrode material to prepare the electrode material and the battery was assembled for electrochemical performance testing.

[0084] Specifically, the prepared medium entropy manganese-based phosphate Na3 (MnVTi) 2 / 3 The (PO4)3 positive electrode material, acetylene black and ketjen black conductive additives, and polyvinylidene fluoride binder are ground and mixed in a mass ratio of 7:1:1:1, and then methyl pyrrolidone solvent is added to obtain a uniform slurry, which is coated on an aluminum foil and cut into sheets with a punching machine after drying to obtain a positive electrode sheet. In an argon glove box, CR2025 button batteries are assembled in the order of negative electrode shell-sodium sheet-electrolyte-diaphragm-electrolyte-positive electrode-positive electrode shell, where the diaphragm is glass fiber and the electrolyte is 1.0M NaPF6. The voltage range of 1.5 to 4.4V was selected to test and collect the CV and constant current charge and discharge data of the battery. The test results are as follows Figure 3-5 shown.

[0085] As you can see, Figure 3 The cyclic voltammetry curve shows four pairs of obvious redox peaks, corresponding to 4.1 / 4.0V (Mn 3+ / Mn 4+ 、V 4+ / V 5+ )、3.5 / 3.4V(Mn 2+ / Mn 3+ 、V 3+ / V 4+)、2.23 / 2.16V(Ti 3+ / Ti 4+ )、1.67 / 1.63V(V 2+ / V 3+ ), it can be seen that multi-electron reaction can occur in Example 1, and all redox couples show lower polarization, indicating that they have fast kinetic characteristics.

[0086] Figure 4 and Figure 5 The positive electrode materials of sodium ion batteries in Example 1 are respectively -1 The charge-discharge curve and cycle curve under current density show that the first cycle discharge capacity of Example 1 reaches 173.10 mAh g -1 After 200 cycles, the specific capacity is still 159.62 mAh g -1 , the capacity retention rate reached 92.2%, showing high specific capacity and excellent cycle performance.

[0087] It can be seen from the test results of this embodiment that the medium-entropy manganese-based phosphate cathode material provided by the present invention has a high discharge specific capacity and good cycle stability, indicating that the local structure of the medium-entropy manganese-based phosphate cathode material can be precisely controlled by regulating the configurational entropy value, thereby inhibiting the formation of Mn 3+ The Jiang-Taylor distortion and reduced polarization improve the electrochemical performance of medium-entropy manganese-based phosphate cathode materials.

[0088] Example 2

[0089] This embodiment provides a medium entropy manganese-based sodium phosphate positive electrode material, the chemical formula of which is Na 11 / 3 (MnFeTi) 2 / 3 (PO4)3, the preparation method of the positive electrode material is:

[0090] According to the stoichiometric ratio, 0.5g of graphene oxide, 1g of carbon nanotubes, 4mmol of manganese acetate tetrahydrate, 4mmol of ferric nitrate nonahydrate, 18mmol of sodium dihydrogen phosphate dihydrate, 4 / 3mmol of anhydrous sodium citrate and 4mmol of di(2-hydroxypropionic acid) diammonium dihydroxide titanium were weighed and put into a ball mill, followed by adding 5mL of isopropanol and 20g of zirconium beads, and the ball mill was placed in a ball mill at 300r / min for 1h. The precursor slurry after ball milling was taken out and placed in an 80℃ forced air oven for drying for 48h, then ground and crushed through a 200-mesh sieve. The precursor powder was placed in a rapid furnace and calcined at 750℃ for 40s to obtain the final sample.

[0091] Example 3

[0092] This embodiment provides a medium entropy manganese-based sodium phosphate positive electrode material, whose chemical formula is Na3(MnTiVAl): 1 / 2(PO4)3, the preparation method of the positive electrode material is:

[0093] According to the stoichiometric ratio, 4g of polyacrylonitrile, 4mmol of manganese acetate tetrahydrate, 4mmol of ammonium metavanadate, 4mmol of sodium dihydrogen phosphate dihydrate, 4 / 3mmol of anhydrous sodium citrate, 4mmol of titanium acetylacetonate and 4mmol of aluminum acetylacetonate were weighed and put into a ball mill, followed by adding 8mL of acetone and 20g of zirconium beads, and the ball mill was placed in a ball mill for 3h at 300r / min. The precursor slurry after ball milling was taken out and placed in an 80℃ forced air oven for drying for 48h, and then ground and crushed through a 100-mesh sieve. The precursor powder was placed in a tubular furnace, heated to 650℃ at 2℃ / min in an argon atmosphere, and sintered for 8h, and finally a chemical formula of Na3(MnTiVAl) was obtained. 1 / 2 (PO4)3 medium-entropy manganese-based phosphate sodium-ion battery positive electrode material powder.

[0094] Example 4

[0095] This embodiment provides a medium entropy manganese-based sodium phosphate cathode material, whose chemical formula is Na3(MnTiCrV) 1 / 2 (PO4)3, the preparation method of the positive electrode material is:

[0096] According to the stoichiometric ratio, 12mmol of glucose, 4mmol of manganese acetate tetrahydrate, 4mmol of ammonium metavanadate, 4mmol of sodium dihydrogen phosphate dihydrate, 4 / 3mmol of anhydrous sodium citrate, 4mmol of titanium acetylacetonate and 4mmol of chromium acetate were weighed and put into a ball mill, followed by adding 10mL of deionized water and 20g of zirconium beads, and the ball mill was placed in a ball mill for 3h at 300r / min. The precursor slurry after ball milling was taken out and placed in a 90℃ forced air oven for drying for 36h, and then ground and crushed through a 100-mesh sieve. The precursor powder was placed in a rotary kiln, heated to 650℃ in an argon atmosphere at 2℃ / min and sintered for 8h, and finally a chemical formula of Na3(MnTiVAl) was obtained. 1 / 2 (PO4)3 medium-entropy manganese-based phosphate sodium-ion battery positive electrode material powder.

[0097] The electrode manufacturing, battery assembly and electrochemical performance testing methods of Examples 2-4 are the same as those of Example 1 and will not be described in detail here.

[0098] Table 1 is a sodium ion battery assembled with the target materials of Examples 1 to 4 as positive electrodes at 100 mA g -1 Electrochemical performance at current density.

[0099] Table 1

[0100]

[0101] As can be seen from Table 1, the medium-entropy manganese-based phosphate cathode material provided by the present invention exhibits high specific capacity, high operating voltage, good cycle stability and excellent rate performance. By regulating the configurational entropy value, the composition and proportion of the material can be optimized, the local structure of the material can be designed, and the Mn 3+ The Jahn-Taylor effect and the charge-discharge process of Na + The stress changes caused by embedding / extraction improve the electrochemical properties of the material.

[0102] It should be noted that the types of sodium source, manganese source, phosphorus source, carbon source and transition metal source in the present application are numerous and are not limited to the materials in Examples 1-4.

[0103] Specifically, the sodium source can be one or more of sodium acetate, sodium oxalate, sodium citrate, sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium dihydrogen phosphate and disodium hydrogen phosphate;

[0104] The manganese source may be one or more of manganese acetate, manganese oxalate, manganese carbonate and manganese acetylacetonate;

[0105] The phosphorus source may be one or more of diammonium phosphate, diammonium hydrogen phosphate, triammonium phosphate, and phosphoric acid;

[0106] The carbon source may be one or more of citric acid, acetic acid, glucose, sucrose, ascorbic acid, malic acid, polyvinylidene fluoride, polyvinyl pyrrolidone, polystyrene, polyacrylonitrile powder, polyethylene terephthalate, polymethyl methacrylate, polyurethane, polylactic acid, graphene, carbon nanotubes and polyvinyl alcohol;

[0107] The transition metal source includes at least two of a titanium source, a vanadium source, an iron source, a chromium source, an aluminum source, a scandium source, a magnesium source, a niobium source, a nickel source, a cobalt source, a molybdenum source, a zirconium source, a copper source, and a gallium source.

[0108] Further, the titanium source may be a mixture of one or more of di(2-hydroxypropionic acid) diammonium dihydroxide titanium, tetrabutyl titanate, isopropyl titanate, tetraethyl titanate, titanium acetylacetonate and titanium dioxide.

[0109] The vanadium source may be one or more of ammonium metavanadate, vanadium oxide, vanadium pentoxide, vanadyl oxalate, vanadyl acetylacetonate and a mixture of vanadium acetylacetonate.

[0110] The iron source may be a mixture of one or more of ferric acetate and its hydrate, ferrous oxalate and its hydrate, ferrous citrate, iron oxide, ferric nitrate and its hydrate.

[0111] The chromium source may be one or more mixtures of chromium acetate, chromium acetate hydroxide and chromium oxide;

[0112] The aluminum source may be a mixture of one or more of aluminum carbonate, aluminum oxalate, and aluminum oxide.

[0113] The scandium source may be one or more of scandium oxide, scandium oxalate, scandium acetate, scandium acetylacetonate and a mixture of hydrates thereof.

[0114] The magnesium source can be one or a mixture of magnesium acetate, magnesium carbonate, and magnesium oxide.

[0115] The niobium source may be one or a mixture of niobium oxide, niobium hydroxide, sodium niobate, niobium ethoxide, hydrated niobium oxalate, ammonium niobate oxalate hydrate.

[0116] The nickel source may be one or more of nickel hydroxide, nickel oxide, nickel acetylacetonate, nickel hydroxyacetate, nickel oxide, nickel peroxide, nickel hypophosphite, nickel oxalate, nickel acetate and a mixture thereof.

[0117] The cobalt source may be a mixture of one or more of cobalt oxide, cobalt carbonate and cobalt acetate.

[0118] The molybdenum source may be one or more mixtures of molybdenum acetylacetonate, molybdenum hexacarbonyl, sodium molybdate dihydrate, molybdenum acetate dimer, molybdenum isopropoxide, ammonium molybdate and hydrates thereof.

[0119] The zirconium source may be one or more mixtures of zirconium acetate, zirconium acetylacetonate, zirconium propionate, ammonium zirconium carbonate, carboxyethyl zirconium acrylate, zirconyl hydroxide, zirconium dioxide, and zirconium hydroxide.

[0120] The copper source may be one or more mixtures of copper citrate, copper acetylacetonate, basic copper carbonate, copper oxalate, copper acetate, copper acetylacetate, copper tartrate hydrate, copper gluconate, copper oxide, copper carbonate and hydrates thereof.

[0121] The gallium source may be one or more of gallium oxide, gallium acetate, gallium nitrate and a mixture thereof.

[0122] In summary, the design principle of the present invention is reliable, the preparation process is simple, easy to control, and has high repeatability. The obtained medium-entropy manganese-based phosphate positive electrode material has excellent electrochemical performance and has great commercial application prospects.

[0123] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A medium entropy manganese-based sodium phosphate cathode material, characterized in that: The medium-entropy sodium manganese phosphate cathode material has a NASICON-type structure, and its chemical formula is Na x (MnM) y (PO4)3, where 2 < x ≤ 5, 0 < y ≤ 1, and M is at least two of Ti, V, Fe, Cr, Al, Sc, Mg, Nb, Ni, Co, Mo, Zr, Cu, and Ga.

2. The medium entropy manganese-based sodium phosphate positive electrode material according to claim 1, characterized in that: The powder particle size distribution of the medium-entropy manganese-based sodium phosphate cathode material is between 100 nm and 10 μm.

3. A method for preparing the medium-entropy manganese-based sodium phosphate positive electrode material according to claim 1 or 2, characterized in that: The following steps are involved: S1, mixing a sodium source, a manganese source, a phosphorus source, a carbon source and a transition metal source in a predetermined ratio to obtain a mixed material; the predetermined ratio is determined according to a calculation formula of a configurational entropy value; the configurational entropy value is between R and 1.5R, wherein R represents an ideal gas constant; The calculation formula of the configuration entropy value is as follows: ΔS conf =-R∑ n i＝1 x i lnx i ; where R is the ideal gas constant, x i represents the mole fraction of the i-th component, and n represents the number of elements; S2, ball milling the mixed material obtained in step S1 to obtain a uniform precursor slurry; S3, drying and pulverizing the precursor slurry obtained in step S2, and then sintering it in an inert gas atmosphere to obtain a medium-entropy manganese-based sodium phosphate cathode material.

4. The method for preparing the medium entropy manganese-based sodium phosphate positive electrode material according to claim 3, characterized in that: The sodium source is one or more of sodium acetate, sodium oxalate, sodium citrate, sodium carbonate, sodium bicarbonate, sodium hydroxide, sodium dihydrogen phosphate and disodium hydrogen phosphate; The manganese source is one or more of manganese acetate, manganese oxalate, manganese carbonate and manganese acetylacetonate; The phosphorus source is one or more of diammonium phosphate, diammonium hydrogen phosphate, triammonium phosphate, and phosphoric acid; The carbon source is one or more of citric acid, acetic acid, glucose, sucrose, ascorbic acid, malic acid, polyvinylidene fluoride, polyvinyl pyrrolidone, polystyrene, polyacrylonitrile powder, polyethylene terephthalate, polymethyl methacrylate, polyurethane, polylactic acid, graphene, carbon nanotubes and polyvinyl alcohol; The transition metal source includes at least two of a titanium source, a vanadium source, an iron source, a chromium source, an aluminum source, a scandium source, a magnesium source, a niobium source, a nickel source, a cobalt source, a molybdenum source, a zirconium source, a copper source, and a gallium source.

5. The method for preparing the medium entropy manganese-based sodium phosphate positive electrode material according to claim 4, characterized in that: The titanium source is one or more mixtures of di(2-hydroxypropionic acid) diammonium dihydroxide titanium, tetrabutyl titanate, isopropyl titanate, tetraethyl titanate, titanium acetylacetonate and titanium dioxide; The vanadium source is one or more mixtures of ammonium metavanadate, vanadium oxide, vanadium pentoxide, vanadyl oxalate, vanadyl acetylacetonate and vanadium acetylacetonate; The iron source is a mixture of one or more of ferric acetate and its hydrate, ferrous oxalate and its hydrate, ferrous citrate, iron oxide, ferric nitrate and its hydrate; The chromium source is one or more mixtures of chromium acetate, chromium acetate hydroxide and chromium oxide; The aluminum source is a mixture of one or more of aluminum carbonate, aluminum oxalate, and aluminum oxide; The scandium source is one or more mixtures of scandium oxide, scandium oxalate, scandium acetate, scandium acetylacetonate and hydrates thereof; The magnesium source is one or more mixtures of magnesium acetate, magnesium carbonate and magnesium oxide; The niobium source is one or more of niobium oxide, niobium hydroxide, sodium niobate, ethoxy niobium, hydrated niobium oxalate, and ammonium niobate oxalate hydrate; The nickel source is one or more of nickel hydroxide, nickel oxide, nickel acetylacetonate, nickel hydroxyacetate, nickel oxide, nickel peroxide, nickel hypophosphite, nickel oxalate, nickel acetate and a mixture thereof; The cobalt source is a mixture of one or more of cobalt oxide, cobalt carbonate and cobalt acetate; The molybdenum source is one or more mixtures of molybdenum acetylacetonate, molybdenum hexacarbonyl, sodium molybdate dihydrate, molybdenum acetate dimer, molybdenum isopropoxide, ammonium molybdate and hydrates thereof; The zirconium source is one or more mixtures of zirconium acetate, zirconium acetylacetonate, zirconium propionate, ammonium zirconium carbonate, carboxyethyl zirconium acrylate, zirconyl hydroxide, zirconium dioxide, and zirconium hydroxide; The copper source is one or more mixtures of copper citrate, copper acetylacetonate, basic copper carbonate, copper oxalate, copper acetate, copper acetylacetate, copper tartrate hydrate, copper gluconate, copper oxide, copper carbonate and hydrates thereof; The gallium source is one or more mixtures of gallium oxide, gallium acetate, gallium nitrate and hydrates thereof.

6. The method for preparing the medium-entropy manganese-based sodium phosphate positive electrode material according to claim 3, characterized in that: In step S2, the solvent medium during the ball milling treatment is water, isopropanol or acetone.

7. The method for preparing the medium entropy manganese-based sodium phosphate positive electrode material according to claim 3, characterized in that: In step S2, during the ball milling process, the mass ratio of zirconium beads to materials is (30-120):1; the main engine speed is 200-400 r / min, and the ball milling time is 0.5-24 h.

8. The method for preparing the medium-entropy manganese-based sodium phosphate positive electrode material according to claim 3, characterized in that: In step S3, the process of drying and pulverizing is as follows: the precursor slurry is placed under a temperature of 80-100° C. and dried by air blast, pulverized by a jet mill, and then passed through a 100-400 mesh sieve to obtain the powder under the sieve.

9. The method for preparing the medium-entropy manganese-based sodium phosphate positive electrode material according to claim 3, characterized in that: In step S3, the powder under the sieve is placed in a rapid reaction furnace, a tubular furnace or a rotary kiln, and sintered in an inert gas atmosphere; when the rapid reaction furnace is used for sintering, the sintering temperature is 700-1000°C, and the time is 10-60s; when the tubular furnace is used for sintering, the temperature is increased to 600-800°C at a heating rate of (2-10)°C / min, and the sintering time is 6-48h; when the rotary kiln is used for sintering, the rotation speed is (1-5)r / min, the temperature is increased to 600-750°C at a heating rate of (2-10)°C / min, and the sintering time is 6-24h; the inert gas is one of argon, nitrogen, carbon monoxide, argon-hydrogen mixed gas and nitrogen-hydrogen mixed gas.

10. An application of a medium entropy manganese-based sodium phosphate positive electrode material, characterized in that: The medium-entropy manganese-based sodium phosphate cathode material is the medium-entropy manganese-based sodium phosphate cathode material according to claim 1 or 2, or is prepared by the preparation method described in any one of claims 3 to 9; the medium-entropy manganese-based sodium phosphate cathode material is used to prepare sodium ion battery electrode materials.

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