High-entropy sulfide negative electrode material and preparation method thereof, negative electrode plate and sodium ion battery

Abstract

The invention relates to a high-entropy sulfide negative electrode material and a preparation method thereof, a negative electrode plate and a sodium ion battery, and belongs to the technical field of battery negative electrode materials. The preparation method of the high-entropy sulfide negative electrode material comprises the following steps: mixing ammonium tetrathiomolybdate, an iron source compound, a cobalt source compound, a nickel source compound, a manganese source compound and a nitrogen-containing organic solvent to obtain a precursor liquid; and putting the precursor liquid into a synthesis device, and then heating in a protective gas environment to obtain the high-entropy sulfide negative electrode material. Wherein the mass ratio of the ammonium tetrathiomolybdate to the iron source compound to the cobalt source compound to the nickel source compound to the manganese source compound is 1: (0.8-3): (0.8-3): (0.8-3): (0.8-3). The preparation method is simple in technological process, the structure and components of the material can be accurately regulated and controlled, and mass production is easy to achieve; the prepared high-entropy sulfide negative electrode material has excellent sodium storage capacity, cycling stability and rate capability.

Description

Technical Field

[0001] The present application relates to the technical field of battery negative electrode materials, and in particular to a high entropy sulfide negative electrode material and a preparation method thereof, a negative electrode sheet, and a sodium ion battery. Background Art

[0002] As an important representative of rechargeable batteries, lithium-ion batteries (LIBs) have become the most widely used secondary power source in applications such as large-scale energy storage, consumer electronic devices, and electric vehicles. However, the scarcity of lithium resources may not be able to meet the expected demand for large-scale grid energy storage in the future. Therefore, it is necessary to find energy storage devices that can replace LIBs to overcome the problems of energy storage system development caused by limited lithium resources. Sodium-ion batteries (SIBs) have attracted much attention due to their low cost and abundant sodium resources (in the earth's crust and seawater). As sodium is in the same main group as lithium, the two have similar physical and chemical properties, which makes sodium ions have great prospects in replacing lithium ions as secondary batteries. However, the current commercial anode materials for sodium-ion batteries are carbon materials, such as hard carbon and soft carbon materials, which have low sodium storage capacity (generally less than 300mAh / g) and poor rate performance, which limits the further improvement of the energy density and fast charging performance of sodium-ion batteries. As a new type of anode material, high-entropy sulfide has the advantages of high sodium storage capacity (generally higher than 500mAh / g) and good rate performance, and shows great application potential in SIBs.

[0003] The methods for synthesizing high-entropy sulfide negative electrode materials reported so far mainly include hydrothermal / solvothermal method, mechanical ball milling method and ultrafast high-temperature impact method. Among them, the preparation conditions of hydrothermal / solvothermal method are mild, which is conducive to the formation of uniform and fine crystals, but the reaction time is long, generally requiring more than ten hours to dozens of hours, and the obtained precursor also needs to be processed by subsequent filtration, washing, drying and high-temperature annealing processes, that is, the preparation process is long and complicated; the mechanical ball milling method can be operated at room temperature without high-temperature heat treatment, but there are lattice defects in the prepared materials, which affect the electrochemical performance, and the ball milling time is often very long, generally dozens of hours, that is, the preparation process is long and the crystal structure is not good; the ultrafast high-temperature impact method has the advantages of fast and efficient, inhibiting the generation of impurities, but it requires high-precision rapid heating equipment, which is costly, and ultrafast heating may cause local overheating or uneven sulfurization, and the amount of material obtained each time is limited by the size of the ultrafast heating substrate, generally less than 5 cm, which makes mass production difficult. Summary of the invention

[0004] In view of the deficiencies in the prior art, the purpose of the embodiments of the present application includes providing a high-entropy sulfide negative electrode material and a preparation method thereof, a negative electrode plate, and a sodium ion battery to improve the sodium storage capacity, cycle performance, and rate performance of the sodium ion battery.

[0005] The embodiment of the present application is implemented as follows:

[0006] In a first aspect, an embodiment of the present application provides a method for preparing a high entropy sulfide negative electrode material, comprising: mixing ammonium tetrathiomolybdate, an iron source compound, a cobalt source compound, a nickel source compound, a manganese source compound, and a nitrogen-containing organic solvent to obtain a precursor liquid; placing the precursor liquid in a gas phase high-pressure reaction device at a reaction pressure of 10-100 MPa, and then heating in a protective gas environment to obtain a high entropy sulfide negative electrode material; wherein the mass ratio of ammonium tetrathiomolybdate, the iron source compound, the cobalt source compound, the nickel source compound and the manganese source compound is 1:(0.8~3):(0.8~3):(0.8~3):(0.8~3).

[0007] The present application uses a material that is easily decomposed at high temperature as a reaction precursor, and by limiting the mass ratio of ammonium tetrathiomolybdate, iron source compound, cobalt source compound, nickel source compound and manganese source compound to 1:(0.8-3):(0.8-3):(0.8-3):(0.8-3), the above reaction precursor is decomposed into a gas phase substance by heat in a gas phase high pressure reaction device, thereby generating high pressure to synthesize a high entropy sulfide negative electrode material. The preparation of high entropy sulfide negative electrode materials by this gas phase high pressure method can increase the reaction rate, and the preparation process is simple. It is only necessary to mix the reaction precursors and add them to the device, and the target material can be obtained after heating, without the need for subsequent filtration, washing, drying and high temperature annealing and other complex processes, that is, the synthesis process is short and simple; and this method can accurately regulate the structure and composition of the negative electrode material, and the output is determined by the size of the device, which is easy to achieve mass production. In addition, the synthesized high-entropy sulfide negative electrode material not only has the characteristics of high-entropy sulfide and good electrochemical properties, but also can improve the sodium storage capacity, cycle performance and rate performance of sodium batteries; and the negative electrode material also contains N-doped carbon, which can effectively improve the conductivity of high-entropy sulfide materials, enhance the electron transfer ability, and improve the rate performance; it can also further inhibit the volume expansion of high-entropy sulfide during sodium storage, thereby enhancing the cycle life of the material.

[0008] In some embodiments of the present application, the iron source compound includes one or more of ferrous oxalate, ferrous nitrate, ferric nitrate, ferric acetate, ferric acrylate, ferric isooctanoate and ferric cyclopentaneate; and / or, the cobalt source compound includes one or more of cobalt oxalate, cobalt nitrate, cobalt acetate, cobalt isooctanoate and cobalt cyclopentaneate.

[0009] In some embodiments of the present application, the nickel source compound includes one or more of nickel oxalate, nickel nitrate, nickel acetate, nickel isooctanoate and nickel cyclopentaneate; and / or, the manganese source compound includes one or more of manganese oxalate, manganese nitrate, manganese acetate, manganese isooctanoate and manganese cyclopentaneate.

[0010] In some embodiments of the present application, the nitrogen-containing organic solvent includes one or more of dimethylammonium propionyl, methylammonium propionyl, dimethylformamide, methylformamide and dimethylacetamide.

[0011] The nitrogen-containing organic solvent can better dissolve the molybdenum source compound, and after high-temperature decomposition, nitrogen-doped carbon can be obtained under the action of high pressure in the gas phase.

[0012] In some embodiments of the present application, the mass ratio of ammonium tetrathiomolybdate to the nitrogen-containing organic solvent is 1:(1.5-2).

[0013] The negative electrode material contains N-doped carbon, wherein the N is derived from the nitrogen-containing organic solvent. Therefore, setting the mass ratio of ammonium tetrathiomolybdate to the nitrogen-containing organic solvent in the range of 1:(1.5-2) is more conducive to the formation of N-doped carbon, thereby improving the electrochemical performance of the negative electrode material.

[0014] In some embodiments of the present application, the high entropy sulfide negative electrode material is a nano-scale powder.

[0015] The high-entropy sulfide negative electrode material prepared in the present application is a nano-scale powder, which has significant advantages as a negative electrode material for sodium ion batteries. Compared with micron-scale materials, nanomaterials can provide a larger specific surface area, increase the contact area between the electrolyte and the active material, and thus make the active material more fully sodium-based, thereby increasing the sodium storage capacity of the active material; the nano-scale size can shorten the transmission distance of sodium ions, thereby improving the rate performance; in addition, the size effect of nano-powder particles helps to alleviate the volume expansion and stress concentration during the sodium ion embedding / de-embedding process, thereby enhancing the cycle life of the material.

[0016] In some embodiments of the present application, the particle size of the powder is 100-200 nm.

[0017] In some embodiments of the present application, the heating temperature is 500-800° C., and the heating time is 2-10 min.

[0018] Within the above-mentioned heating temperature and time range, the reaction rate can be accelerated, and within the above-mentioned temperature range, precursors such as molybdenum source compounds can be rapidly decomposed to release gaseous or solid substances containing molybdenum, iron, cobalt, nickel, manganese, and sulfur, thereby promoting the rapid synthesis of high-entropy sulfides under the action of high pressure; the microstructure of the reaction can also be effectively controlled, promoting uniform distribution of components, and being beneficial to improving the electrochemical properties of the obtained high-entropy sulfide negative electrode material.

[0019] In a second aspect, an embodiment of the present application provides a high entropy sulfide negative electrode material, which is prepared by any of the above-mentioned preparation methods.

[0020] This high-entropy sulfide negative electrode material not only has the characteristics of high-entropy sulfide and good electrochemical properties, and can improve the sodium storage capacity, cycle performance and rate performance of sodium batteries; it also has N-doped carbon, which can effectively improve the conductivity of the composite material, enhance the electron transfer ability, and improve the rate performance; and the N-doped carbon can further inhibit the volume expansion during the high-entropy sulfide sodium storage process, thereby enhancing the cycle life of the material.

[0021] In a third aspect, an embodiment of the present application provides a negative electrode plate, comprising the above-mentioned high entropy sulfide negative electrode material.

[0022] This high-entropy sulfide negative electrode material has good conductivity and high capacity, as well as good cycle performance and rate performance, which can improve the overall performance of the battery, extend its service life, and can also be adapted to application scenarios of fast charging and high power output.

[0023] In a fourth aspect, an embodiment of the present application provides a sodium ion battery, comprising the above-mentioned negative electrode plate.

[0024] Sodium-ion batteries using this high-entropy sulfide negative electrode material can achieve higher sodium storage capacity, cycle performance and rate performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 This is a SEM image of the high entropy sulfide negative electrode material prepared in Example 1 of the present application;

[0027] Figure 2 This is the Raman spectrum of the high entropy sulfide negative electrode material prepared in Example 1 of the present application;

[0028] Figure 3 This is a SEM image of the high entropy sulfide negative electrode material prepared in Example 2 of the present application;

[0029] Figure 4 This is the Raman spectrum of the high entropy sulfide negative electrode material prepared in Example 2 of the present application;

[0030] Figure 5 This is the XPS spectrum of the high entropy sulfide negative electrode material prepared in Example 2 of the present application; wherein, Figure 5 a is the full XPS spectrum of the negative electrode material. Figure 5 b is the XPS high-resolution spectrum of Fe2p of the negative electrode material. Figure 5 c is the XPS high-resolution spectrum of Co2p of the negative electrode material. Figure 5 d is the XPS high-resolution spectrum of Ni2p of the negative electrode material. Figure 5 e is the XPS high-resolution spectrum of Mn2p of the negative electrode material. Figure 5 f is the XPS high-resolution spectrum of Mo3d of the negative electrode material, Figure 5 g is the XPS high-resolution spectrum of S2p of the negative electrode material, Figure 5 h is the XPS high-resolution spectrum of C1s of the negative electrode material;

[0031] Figure 6 This is the XPS high-resolution spectrum of the high-entropy sulfide negative electrode material N1s prepared in Example 2 of the present application;

[0032] Figure 7 This is a SEM image of the high entropy sulfide negative electrode material prepared in Example 4 of the present application;

[0033] Figure 8 This is a SEM image of the high entropy sulfide negative electrode material prepared in Comparative Example 1 of the present application;

[0034] Fig. 9 This is a SEM image of the high entropy sulfide negative electrode material prepared in Example 3 of the present application;

[0035] Fig.10 This is a SEM image of the high entropy sulfide negative electrode material prepared in Comparative Example 2 of the present application;

[0036] Fig.11 This is a SEM image of the high entropy sulfide negative electrode material prepared in Comparative Example 4 of the present application. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0038] The following is a detailed description of a high entropy sulfide negative electrode material and a preparation method thereof, a negative electrode plate, and a sodium ion battery in an embodiment of the present application.

[0039] The present invention provides a method for preparing a high entropy sulfide negative electrode material, and the preparation method comprises the following steps:

[0040] (1) Ammonium tetrathiomolybdate, an iron source compound, a cobalt source compound, a nickel source compound, a manganese source compound and a nitrogen-containing organic solvent are uniformly mixed in a beaker as reaction precursors to obtain a precursor liquid; wherein the mass ratio of ammonium tetrathiomolybdate, the iron source compound, the cobalt source compound, the nickel source compound and the manganese source compound is 1:(0.8-3):(0.8-3):(0.8-3):(0.8-3).

[0041] The iron source compound includes but is not limited to one or more of ferrous oxalate, ferrous nitrate, ferric nitrate, ferric acetate, ferric acrylate, ferric isooctanoate and ferric naphthenate; the cobalt source compound includes but is not limited to one or more of cobalt oxalate, cobalt nitrate, cobalt acetate, cobalt isooctanoate and cobalt naphthenate. The nickel source compound includes but is not limited to one or more of nickel oxalate, nickel nitrate, nickel acetate, nickel isooctanoate and nickel naphthenate; the manganese source compound includes but is not limited to one or more of manganese oxalate, manganese nitrate, manganese acetate, manganese isooctanoate and manganese naphthenate.

[0042] The nitrogen-containing organic solvent includes, but is not limited to, one or more of dimethylammonium propionyl, methylammonium propionyl, dimethylformamide, methylformamide and dimethylacetamide.

[0043] Wherein, the mass ratio of ammonium tetrathiomolybdate to the nitrogen-containing organic solvent is 1:(1.5-2).

[0044] As an example, the mass ratio of ammonium tetrathiomolybdate to the nitrogen-containing organic solvent includes but is not limited to 1:1.5, 1:1.6, 1:1.7, 1:1.8, 1:1.9, 1:2.

[0045] (2) The precursor liquid prepared in step (1) is transferred to a high-pressure reactor device with a reaction pressure of 10-100 MPa and sealed under an argon atmosphere.

[0046] The high-pressure reactor used in the present application can withstand a maximum temperature of up to 900°C and a pressure of up to 50 MPa. High temperature and high pressure can promote the rapid progress of the reaction, shorten the preparation time, and increase the reaction rate.

[0047] (3) The high-pressure reactor device in step (2) is transferred to a tubular furnace filled with protective gas and heated to obtain a high-entropy sulfide negative electrode material.

[0048] A high-entropy sulfide negative electrode material is prepared by a gas-phase high-pressure method. The negative electrode material is a composite of high-entropy sulfide and N-doped carbon material. On the one hand, the characteristics of high-entropy sulfide give the negative electrode material excellent electrochemical properties; on the other hand, N-doped carbon can effectively improve the conductivity of the composite material, enhance the electron transfer ability, and improve the rate performance; and N-doped carbon can also further inhibit the volume expansion of high-entropy sulfide during sodium storage, thereby enhancing the cycle life of the material.

[0049] The high entropy sulfide negative electrode material in the present application is a nano-scale powder, and optionally, the particle size of the powder is 100-200nm.

[0050] Nanoscale powders can provide a larger specific surface area, increase the contact area between the electrolyte and the active material, and make the active material more fully sodium-based, thereby increasing the sodium storage capacity of the active material; and the nanoscale size can shorten the transmission distance of sodium ions, thereby improving the rate performance; it also helps to alleviate the volume expansion and stress concentration during the sodium ion embedding / de-embedding process, and N-doped carbon can further inhibit the volume expansion during the high entropy sulfide sodium storage process, thereby enhancing the cycle life of the material.

[0051] In the present application, the heating temperature is 500-800° C., and the heating time is 2-10 min.

[0052] By way of example, the heating temperature includes, but is not limited to, 500°C, 550°C, 600°C, 650°C, 700°C, 750°C, and 800°C.

[0053] (4) Remove and open the reaction device in a fume hood while wearing protective tools, and carefully pour out the prepared high-entropy sulfide negative electrode material into a sample bottle for sealed storage.

[0054] This application effectively suppresses the lattice structure changes and volume expansion of electrode materials during ion embedding or de-embedding by improving the configurational entropy, thereby significantly improving the cycle stability and service life of battery materials. In addition, the high entropy strategy can also effectively alleviate or suppress adverse phase changes during charging and discharging, which often lead to battery performance degradation, such as structural collapse and capacity decay. The lattice distortion caused by the introduction of multiple elements can form low-energy ion diffusion paths, thereby significantly improving the ionic conductivity of the material; at the same time, the additional lattice disorder in the high entropy material provides more paths for ion migration, further optimizing the diffusion kinetics of the electrode material. In addition, the composite of high entropy sulfide and N-doped carbon material can not only effectively alleviate the volume expansion of high entropy sulfide during charging and discharging, prevent its structural collapse or pulverization, but also enhance the overall conductivity of the composite material, thereby further improving the cycle stability and rate performance of the electrode.

[0055] The present application also provides a negative electrode sheet, the preparation method of which comprises the following steps:

[0056] The high entropy sulfide and N-doped carbon composite nanopowder material synthesized by the above preparation scheme is used as the active material, and is evenly mixed with acetylene black (conductive agent) and polyvinylidene fluoride (PVDF, binder) at a mass ratio of 8:1:1 and dispersed in N-methylpyrrolidone (NMP). First, PVDF is dissolved in NMP. After the liquids are evenly mixed, the active material and acetylene black are added. The two need to be pre-mixed by grinding before adding, and magnetic stirring is applied at the same time. After stirring evenly (~24h), it is applied on the copper foil with a coater according to a certain thickness, and then transferred to a drying oven, first dried at 50°C at normal pressure for 4-6h to remove the macromolecular solvent, and then dried at 80°C in vacuum for 12h. After the end, the discs are taken out and cut into 12mm diameter discs, weighed and placed in a glove box filled with argon (H2O<0.01ppm and O2<0.01ppm) for standby use.

[0057] The present invention also provides a sodium ion battery, wherein the preparation method thereof comprises the following steps:

[0058] The assembly process was carried out in a glove box filled with argon atmosphere, wherein the electrode shell used a 2032 button half-cell, the pole piece was the above-prepared disc placed in the glove box, the diaphragm used a Whatman glass fiber membrane, the counter electrode and the reference electrode were sodium sheets, the electrolyte was 1M NaPF6 dissolved in diethylene glycol dimethyl ether, and the supporting and conductive material was nickel foam with a diameter of 16 mm and thicknesses of 1.5 mm and 1 mm respectively.

[0059] The features and performance of the present application are further described in detail below in conjunction with the embodiments.

[0060] Example 1

[0061] This embodiment provides a method for preparing a high entropy sulfide negative electrode material, and the preparation method comprises the following steps:

[0062] (1) Ammonium tetrathiomolybdate, iron isooctanoate, cobalt isooctanoate, nickel isooctanoate, manganese isooctanoate and dimethylacetamide are uniformly mixed in a beaker as reaction precursors in a mass ratio of 1:3:3:3:3:2 to obtain a precursor liquid.

[0063] (2) The precursor liquid prepared in step (1) is transferred to a high-pressure reactor and sealed under an argon atmosphere.

[0064] (3) The high-pressure reactor in step (2) is transferred to a tubular furnace filled with argon gas, and maintained at a temperature of 500° C. for 10 min to obtain a high-entropy sulfide negative electrode material.

[0065] Example 2

[0066] This embodiment provides a method for preparing a high entropy sulfide negative electrode material, and the preparation method comprises the following steps:

[0067] (1) Ammonium tetrathiomolybdate, ferrous oxalate, cobalt oxalate, nickel oxalate, manganese oxalate and methylformamide in a mass ratio of 1:0.8:0.8:0.8:0.8:1.5 as reaction precursors are uniformly mixed in a beaker to obtain a precursor liquid.

[0068] (2) The precursor liquid prepared in step (1) is transferred to a high-pressure reactor and sealed under an argon atmosphere.

[0069] (3) The high-pressure reactor in step (2) is transferred to a tubular furnace filled with argon gas, and maintained at a temperature of 800° C. for 2 minutes to obtain a high-entropy sulfide negative electrode material.

[0070] Example 3

[0071] This comparative example provides a method for preparing a high entropy sulfide negative electrode material, and the preparation method comprises the following steps:

[0072] (1) Ammonium tetrathiomolybdate, ferrous oxalate, cobalt oxalate, nickel oxalate, manganese oxalate and methylformamide in a mass ratio of 1:0.8:0.8:0.8:0.8:3 as reaction precursors are uniformly mixed in a beaker to obtain a precursor liquid.

[0073] (2) The precursor liquid prepared in step (1) is transferred to a high-pressure reactor and sealed under an argon atmosphere.

[0074] (3) The high-pressure reactor in step (2) is transferred to a tubular furnace filled with argon gas, and maintained at a temperature of 800° C. for 2 minutes to obtain a high-entropy sulfide negative electrode material.

[0075] Example 4

[0076] This embodiment provides a method for preparing a high entropy sulfide negative electrode material, and the preparation method comprises the following steps:

[0077] (1) Ammonium tetrathiomolybdate, ferrous oxalate, cobalt oxalate, nickel oxalate, manganese oxalate and methylformamide in a mass ratio of 1:0.8:0.8:0.8:0.8:1.5 as reaction precursors are uniformly mixed in a beaker to obtain a precursor liquid.

[0078] (2) The precursor liquid prepared in step (1) is transferred to a high-pressure reactor and sealed under an argon atmosphere.

[0079] (3) The high-pressure reactor in step (2) is transferred to a tubular furnace filled with argon gas, and maintained at a temperature of 850° C. for 2 min to obtain a high-entropy sulfide negative electrode material.

[0080] Comparative Example 1

[0081] This comparative example provides a method for preparing a high entropy sulfide negative electrode material, and the preparation method comprises the following steps:

[0082] (1) Ammonium tetrathiomolybdate, iron isooctanoate, cobalt isooctanoate, nickel isooctanoate, manganese isooctanoate and dimethylacetamide as reaction precursors in a mass ratio of 1:4:3:3:3:2 are uniformly mixed in a beaker to obtain a precursor liquid.

[0083] (2) The precursor liquid prepared in step (1) is transferred to a high-pressure reactor and sealed under an argon atmosphere.

[0084] (3) The high-pressure reactor in step (2) is transferred to a tubular furnace filled with argon gas, and maintained at a temperature of 500° C. for 10 min to obtain a high-entropy sulfide negative electrode material.

[0085] Comparative Example 2

[0086] This comparative example provides a method for preparing a high entropy sulfide negative electrode material, and the preparation method comprises the following steps:

[0087] (1) Ammonium tetrathiomolybdate, ferrous oxalate, cobalt oxalate, nickel oxalate, manganese oxalate and methylformamide in a mass ratio of 1:0.8:0.8:0.8:0.8:1 as reaction precursors are uniformly mixed in a beaker to obtain a precursor liquid.

[0088] (2) The precursor liquid prepared in step (1) is transferred to a high-pressure reactor and sealed under an argon atmosphere.

[0089] (3) The high-pressure reactor in step (2) is transferred to a tubular furnace filled with argon gas, and maintained at a temperature of 800° C. for 2 minutes to obtain a high-entropy sulfide negative electrode material.

[0090] Comparative Example 3

[0091] This comparative example provides a method for preparing a high entropy sulfide negative electrode material, and the preparation method comprises the following steps:

[0092] (1) Ammonium tetrathiomolybdate, ferrous oxalate, cobalt oxalate, nickel oxalate, manganese oxalate and methylformamide in a mass ratio of 1:0.4:0.4:0.4:0.4:1.5 as reaction precursors are uniformly mixed in a beaker to obtain a precursor liquid.

[0093] (2) The precursor liquid prepared in step (1) is transferred to a high-pressure reactor and sealed under an argon atmosphere.

[0094] (3) The high-pressure reactor in step (2) is transferred to a tubular furnace filled with argon gas, and maintained at a temperature of 800° C. for 2 minutes to obtain a high-entropy sulfide negative electrode material.

[0095] Comparative Example 4

[0096] This embodiment provides a method for preparing a high entropy sulfide negative electrode material, and the preparation method comprises the following steps:

[0097] Mo, Fe, Co, Ni, Mn and S powders with a mass ratio of 1:0.6:0.6:0.6:0.6:2.5 were used as precursors and milled at room temperature for 48 hours at a speed of 500rpm in a high-energy planetary ball mill in a high-purity argon atmosphere. A 50mL ball milling jar and a 5mm diameter ball were used, and the weight ratio of the ball to the powder was 25:1; the powder material obtained after ball milling was the high-entropy sulfide material; this material and methylformamide were then added to a gas phase high-pressure reactor in a mass ratio of 1:1.5, heated to 800°C, and kept warm for 2 minutes, thereby obtaining a negative electrode material of high-entropy sulfide and N-doped carbon composite.

[0098] Some parameters of the above embodiments and comparative examples are shown in Table 1.

[0099] Table 1

[0100]

[0101] Test Example 1

[0102] In this test example, SEM (Scanning Electron Microscope), Raman (Raman spectra), XPS (Xray Photoelectron Spectroscopy), ICP-AES (Inductively Coupled Plasma-Atomic Emission Spectrometer) and C / S element analyzer were used to characterize the high entropy sulfide negative electrode materials prepared in Examples 1-4 and Comparative Examples 1 and 2.

[0103] in, Figure 1 This is a SEM image of the high entropy sulfide negative electrode material prepared in Example 1 of the present application; Figure 2 This is the Raman spectrum of the high entropy sulfide negative electrode material prepared in Example 1 of the present application; Figure 3This is a SEM image of the high entropy sulfide negative electrode material prepared in Example 2 of the present application; Figure 4 This is the Raman spectrum of the high entropy sulfide negative electrode material prepared in Example 2 of the present application; Figure 5 This is the XPS spectrum of the high entropy sulfide negative electrode material prepared in Example 2 of the present application; wherein, Figure 5 a is the full XPS spectrum of the negative electrode material. Figure 5 b is the XPS high-resolution spectrum of Fe2p of the negative electrode material. Figure 5 c is the XPS high-resolution spectrum of Co2p of the negative electrode material. Figure 5 d is the XPS high-resolution spectrum of Ni2p of the negative electrode material. Figure 5 e is the XPS high-resolution spectrum of Mn2p of the negative electrode material. Figure 5 f is the XPS high-resolution spectrum of Mo3d of the negative electrode material, Figure 5 g is the XPS high-resolution spectrum of S2p of the negative electrode material, Figure 5 h is the XPS high-resolution spectrum of C1s of the negative electrode material; Figure 6 This is the XPS high-resolution spectrum of the high-entropy sulfide negative electrode material N1s prepared in Example 2 of the present application; Figure 7 This is a SEM image of the high entropy sulfide negative electrode material prepared in Example 4 of the present application; Figure 8 This is a SEM image of the high entropy sulfide negative electrode material prepared in Comparative Example 1 of the present application; Fig. 9 This is a SEM image of the high entropy sulfide negative electrode material prepared in Example 3 of the present application; Fig.10 This is a SEM image of the high entropy sulfide negative electrode material prepared in Comparative Example 2 of the present application; Fig.11 This is a SEM image of the high entropy sulfide negative electrode material prepared in Comparative Example 4 of this application; please refer to Figure 1-Figure 11 .

[0104] from Figure 1 A large number of randomly distributed particles can be seen in the figure. The particles have irregular shapes and are highly stacked. The particle surface is not smooth and has a high degree of roughness. There are gaps between the particles, and the size range is 100-200nm. Figure 2 The Raman spectrum shows that at 1365.6 cm -1 and 1587.3cm -1 The D peak and G peak unique to carbon materials appeared at the positions, respectively, proving that the carbon composite was successfully carried out on the material. In addition, the ICP-AES element analysis test results showed that the mass fractions of Fe, Co, Ni, Mn, Mo, S, C and N elements in the negative electrode material prepared in Example 1 were 8.63, 9.09, 8.34, 7.91, 16.76, 32.87, 14.78 and 1.62, respectively. The high entropy sulfide molecular formula was calculated to be Fe 0.15 Co0.15 Ni 0.14 Mn 0.14 Mo 0.17 S. Since the definition of high entropy compounds requires that the molar ratios of five or more elements need to be equal or close, it can be seen from the molecular formula that the molar ratios of the five metal elements Fe, Co, Ni, Mn and Mo are close, which meets the definition of high entropy materials.

[0105] from Figure 3 It can be seen that it exhibits a similar morphology to the negative electrode material of Example 1; Figure 4 The Raman spectrum shows that at 1354.6 cm -1 and 1587.4cm -1 The D peak and G peak unique to carbon materials appeared at , proving that the carbon composite of the material was successfully carried out; Figure 5 and Figure 6 It can be seen from the XPS spectrum that Fe2p of Fe element appears at 711.1 and 724.6 eV 3 / 2 and Fe 2p 1 / 2 The characteristic peak, Co 2p of Co element, appears at 793.1eV 1 / 2 Characteristic peaks, Ni 2p of Ni element, appeared at 854.5 and 874.1 eV 3 / 2 and Ni 2p 1 / 2 Characteristic peaks, Mn 2p of Mn element appeared at 642.5 and 653.9 eV 3 / 2 and Mn 2p 1 / 2 Characteristic peaks, Mo 3d of Mo element, appeared at 229.1 and 232.2 eV 5 / 2 and Mo 3d 3 / 2 Characteristic peaks, S2p of S element appeared at 161.8 and 162.8 eV 3 / 2 and S2p 1 / 2 Characteristic peaks. The above experimental results show that the negative electrode material contains Fe, Co, Ni, Mn, Mo and S elements. In addition, it can be seen that the C=C, CO / CN and C=O characteristic peaks of the C element appear at 284.2, 285.5 and 287.5 eV, indicating that the C element exists in the negative electrode material and this carbon element is doped with N. A broad peak appears at 397.2 to 402.0 eV, which is the peak of pyridine N, pyrrole N and graphite N, further proving that the carbon material in the negative electrode material is doped with N. In addition, the ICP-AES and elemental analysis test results show that the mass fractions of Fe, Co, Ni, Mn, Mo, S, C and N elements in the negative electrode material prepared in Example 2 are 9.71, 9.09, 8.94, 7.41, 15.71, 30.81, 16.06 and 2.27, respectively. The calculated molecular formula is Fe0.18 Co 0.16 Ni 0.16 Mn 0.15 Mo 0.17 S, as can be seen from the molecular formula, the molar ratios of the five metal elements Fe, Co, Ni, Mn and Mo are close, which meets the definition of high entropy materials.

[0106] from Figure 7 It can be seen that the negative electrode material prepared in Example 4 has a large number of randomly distributed nano-sized particles similar to those in Example 2, and also has some micron-sized block and spherical particles with smooth surfaces. This is because as the reaction temperature increases, some impurities are generated in the negative electrode material.

[0107] from Fig. 9 It can be seen that the morphology of the negative electrode material prepared in Example 3 is similar to that in Example 2, except that the morphology of the nanoparticles is reduced, which may be caused by more carbon coating. The ICP-AES element analysis test results show that the mass fractions of Fe, Co, Ni, Mn, Mo, S, C and N elements in the negative electrode material prepared in Comparative Example 3 are 8.56, 8.49, 8.35, 7.91, 13.81, 28.78, 21.54 and 2.56, respectively. The high entropy sulfide molecular formula is calculated to be Fe 0.17 Co 0.16 Ni 0.16 Mn 0.16 Mo 0.17 S, from which it can also be seen that the proportion of C element increases from 16.06wt% in Example 2 to 21.54wt%.

[0108] from Figure 8 It can be seen that in addition to showing a similar morphology to the high entropy sulfide negative electrode material in Example 1, the negative electrode material prepared in Comparative Example 1 also presents many clear flake structures with a size of about 1 to 5 microns, and these crystals have high regularity. Fig.10 It can be seen that the morphology of the negative electrode material prepared in Comparative Example 3 is similar to that in Example 2. The ICP-AES element analysis test results show that the mass fractions of Fe, Co, Ni, Mn, Mo, S, C, and N in the negative electrode material prepared in Comparative Example 3 are 4.49, 4.14, 4.07, 4.41, 33.66, 32.06, 35.14, and 1.93, respectively. The corresponding molecular formula is calculated to be Fe 0.08 Co 0.07 Ni 0.08 Mn 0.08 Mo 0.35 S, it can be seen that since the molar ratio of Mo element is much larger than that of other metal elements, the prepared negative electrode material does not have the characteristics of high entropy compounds.

[0109] from Fig.11 It can be seen that the morphology of the high entropy sulfide obtained by the ball milling method in Comparative Example 4 is nano-scale particles with a size range of 200-600nm. The ICP-AES element analysis test results show that the mass fractions of Fe, Co, Ni, Mn, Mo, S, C, and N in the negative electrode material prepared in Comparative Example 4 are 8.32, 8.48, 8.34, 8.14, 13.86, 34.64, 16.08, and 2.14, respectively. The calculated molecular formula is Fe 0.14 Co 0.13 Ni 0.13 Mn 0.14 Mo 0.13 S, as can be seen from the molecular formula, the molar ratios of the five metal elements Fe, Co, Ni, Mn and Mo are close, which meets the definition of high entropy materials.

[0110] Test Example 2

[0111] In this test example, the high entropy sulfide negative electrode materials prepared in Examples 1-4 and Comparative Examples 1-4 were used as negative electrode materials for sodium ion batteries to prepare sodium ion batteries, and then the above batteries were subjected to performance tests, including: initial charge and discharge capacity, initial coulombic efficiency, cycle performance, and rate performance. Among them, the preparation process of the sodium ion battery is as follows: each high entropy sulfide negative electrode material is mixed with acetylene black and PVDF in a mass ratio of 8:1:1, and added to NMP for magnetic stirring. After 24 hours, it is evenly applied on the copper foil current collector, and then transferred to a vacuum drying oven. First, it is dried at 50°C at normal pressure for 6 hours to remove the macromolecular solvent, and then dried at 80°C in vacuum for 12 hours. After the end, it is taken out and cut into 12mm diameter discs and placed in a glove box filled with argon; then the battery is assembled, and the assembly process is carried out in a glove box filled with argon atmosphere, wherein the electrode shell uses a 2032 button half-cell, the pole piece is the above-prepared disc placed in the glove box, the diaphragm uses a Whatman glass fiber membrane, the counter electrode and the reference electrode are sodium sheets, the electrolyte is 1M NaPF6 dissolved in diethylene glycol dimethyl ether, and the material with supporting and conductive functions uses nickel foam with a diameter of 16mm and thicknesses of 1.5mm and 1mm respectively.

[0112] The electrochemical performance test was completed on a Xinwei battery tester (model MIHW-200-160CH-B) with a constant test temperature of 25°C, a test voltage range of 0.01-3V and a current density of 0.1-20C (1C=650mA / g).

[0113] Please see Table 2 for the results of the above performance tests.

[0114] Table 2

[0115]

[0116]

[0117] Table 3

[0118]

[0119] As can be seen from Table 2, the high entropy sulfide negative electrode materials prepared in Examples 1 and 2 of the present application are used as negative electrode materials for sodium ion batteries. At a current density of 0.1C, the first discharge capacity is 748.7 mAh / g and 770.0 mAh / g, respectively, the first charge capacity is 653.6 mAh / g and 676.8 mAh / g, respectively, and the first coulombic efficiency is 87.3% and 87.9%, respectively, indicating that the high entropy sulfide negative electrode material provided in the present application has an ultra-high sodium storage capacity and a good first coulombic efficiency. Moreover, at a current density of 0.1C, the reversible capacities of the sodium ion batteries prepared from the negative electrode materials of Example 1 and Example 2 after 100 cycles were 647.1 mAh / g and 671.4 mAh / g, respectively; the reversible capacities obtained after 6000 cycles at a current density of 10C were 444.8 mAh / g and 481.9 mAh / g, respectively; indicating that the high entropy sulfide negative electrode material provided in the present application has excellent cycle stability, and still has excellent stability even after thousands of cycles at a high current density of 10C.

[0120] It can be seen from the data in Table 3 that the sodium ion batteries prepared by the negative electrode materials of Example 1 and Example 2 are still stable during high-rate charge and discharge, and the capacities obtained at 20C can maintain 62.1% and 63.6% of the 0.1C capacity, respectively, indicating that the high-entropy sulfide negative electrode material provided in the present application has excellent rate performance.

[0121] In Example 3, the proportion of methylformamide is increased, so that the carbon content in the prepared negative electrode material is increased, and the sodium storage capacity of the carbon material is lower than that of the high entropy sulfide, so the increase in its content will reduce the sodium storage capacity of the negative electrode material at different current densities; in Example 4, the heating temperature is increased, so that micron-sized block and spherical particle impurities are produced in the negative electrode material, and these impurities are not conducive to the rapid transmission and storage of sodium ions, thereby reducing the corresponding capacity, cycle performance and rate performance.

[0122] In Comparative Example 1, the proportion of iron isooctanoate is increased, so that a micron-sized flaky impurity phase is produced in the prepared negative electrode material, which is not conducive to the rapid transmission and storage of sodium ions, thereby reducing the corresponding capacity, cycle performance and rate performance; in Comparative Example 2, the proportion of methylformamide is reduced, so that the carbon content in the prepared negative electrode material is reduced, resulting in a reduction in the effect of carbon materials on improving the conductivity of high entropy sulfides and a reduction in the ability of carbon materials to alleviate the volume expansion of high entropy sulfides, thereby reducing the capacity, cycle performance and rate performance. The negative electrode material prepared in Comparative Example 3 does not have the characteristics of high entropy compounds, thereby reducing the corresponding capacity, cycle performance and rate performance. The particle size of the high entropy sulfide negative electrode material prepared by ball milling in Comparative Example 4 is significantly higher than that obtained by the gas phase high pressure method in the present application. The large size is not conducive to the transmission of sodium ions and the corresponding volume expansion effect will be greater, thereby reducing the corresponding capacity, cycle performance and rate performance.

[0123] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

Claims

1. A method for preparing a high entropy sulfide negative electrode material, characterized in that: include: ammonium tetrathiomolybdate, an iron source compound, a cobalt source compound, a nickel source compound, a manganese source compound, and a nitrogen-containing organic solvent are mixed to obtain a precursor liquid; Placing the precursor liquid in a gas phase high pressure reaction device at a reaction pressure of 10-100 MPa, and then heating in a protective gas environment to obtain the high entropy sulfide negative electrode material; Among them, the mass ratio of the ammonium tetrathiomolybdate, the iron source compound, the cobalt source compound, the nickel source compound and the manganese source compound is 1:(0.8-3):(0.8-3):(0.8-3):(0.8-3).

2. The preparation method according to claim 1, characterized in that: The iron source compound includes one or more of ferrous oxalate, ferrous nitrate, ferric nitrate, ferric acetate, ferric acrylate, ferric isooctanoate and ferric naphthenate; And / or, the cobalt source compound includes one or more of cobalt oxalate, cobalt nitrate, cobalt acetate, cobalt isooctanoate and cobalt naphthenate.

3. The preparation method according to claim 1, characterized in that: The nickel source compound includes one or more of nickel oxalate, nickel nitrate, nickel acetate, nickel isooctanoate and nickel naphthenate; And / or, the manganese source compound includes one or more of manganese oxalate, manganese nitrate, manganese acetate, manganese isooctanoate and manganese naphthenate.

4. The preparation method according to any one of claims 1 to 3, characterized in that The nitrogen-containing organic solvent includes one or more of dimethyl propionyl ammonium, methyl propionyl ammonium, dimethylformamide, methylformamide and dimethylacetamide.

5. The preparation method according to claim 4, characterized in that: The mass ratio of the ammonium tetrathiomolybdate to the nitrogen-containing organic solvent is 1:(1.5-2).

6. The preparation method according to any one of claims 1 to 3, characterized in that: The high entropy sulfide negative electrode material is a nanometer-scale powder; Optionally, the particle size of the powder is 100-200 nm.

7. The preparation method according to any one of claims 1 to 3, characterized in that: The heating temperature is 500-800° C., and the heating time is 2-10 min.

8. A high entropy sulfide negative electrode material, characterized in that: Prepared by the preparation method described in any one of claims 1 to 7.

9. A negative electrode plate, characterized in that: Comprising the high entropy sulfide negative electrode material as described in claim 8.

10. A sodium ion battery, characterized in that: The invention comprises the negative electrode sheet as claimed in claim 9.

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