High-entropy alloy oxide composite material and preparation method and application thereof

Abstract

The invention provides a high-entropy alloy oxide composite material and a preparation method and application thereof. According to the high-entropy alloy oxide composite material, the chemical composition of the high-entropy alloy oxide composite material is CeNiFeCuCoOx-SiWA, the value range of x ranges from 5 to 7.5, and SiWA is silicotungstic acid. The composite material is used as a lithium ion battery negative electrode material, and has good cycling stability and rate capability. The invention further provides a preparation method and application of the high-entropy alloy oxide composite material.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-entropy alloys, and particularly relates to a high-entropy alloy oxide composite material, a preparation method thereof, and an application thereof. Background Art

[0002] In the context of the increasingly prominent energy and environmental issues today, secondary batteries have become an important technology for promoting sustainable development due to their key role in energy storage, clean energy applications, and carbon emission reduction. Among various types of secondary batteries, lithium-ion batteries have been widely studied due to their advantages such as high energy density, high power density, and long cycle life. Among them, the negative electrode material is an important part of the lithium-ion battery and has an important impact on the electrochemical performance of the lithium-ion battery. Currently, graphite-type carbon negative electrodes and silicon-based negative electrode materials are the mainstream negative electrode materials in lithium-ion batteries. Among them, the graphite carbon negative electrode is limited by a relatively low theoretical capacity (theoretical specific capacity is 372 mAh·g -1 ), and it is difficult to meet the rapid development needs of high-energy density batteries. Although silicon-based materials have a capacity advantage, their volume will expand violently (>300%) during the charge / discharge process, resulting in particle pulverization and electrode structure collapse, leading to problems such as a sharp drop in cycle stability, Coulomb efficiency decay, and shortened battery life. Therefore, the development of new negative electrode materials with high specific capacity, low volume strain, and long cycle life has become a research hotspot in the field of lithium-ion batteries.

[0003] Metal negative electrodes (alloy-type negative electrodes) have a relatively high theoretical capacity and a relatively low electrode potential. Through the synergistic interaction of multiple metals and structural design, they can reduce the stress of lithium insertion / extraction, thereby effectively suppressing the occurrence of particle pulverization and electrode failure, and becoming the core technical direction for breaking through the performance bottleneck of lithium-ion batteries. Among them, high-entropy alloy oxides are expected to become potential negative electrode materials due to their characteristics such as single-phase structure, high-entropy effect, lattice distortion effect, and synergistic effect. However, the traditional preparation methods of high-entropy alloy oxides usually require high-temperature conditions (600 - 1600 °C), and the high energy consumption limits their practical applications.

[0004] Therefore, it is necessary to develop a new lithium-ion battery negative electrode material to solve the problem of limited application of traditional high-entropy alloy oxides in negative electrode materials. Summary of the Invention

[0005] The present invention aims to solve at least one of the above technical problems existing in the prior art. For this reason, the present invention provides a high-entropy alloy oxide composite material, which has good cycle stability and rate performance when used as a lithium-ion battery negative electrode material.

[0006] The present invention also provides a preparation method of the high-entropy alloy oxide composite material.

[0007] The present invention also provides a negative electrode material for a lithium-ion battery.

[0008] In a first aspect of the present invention, a high-entropy alloy oxide composite material is provided. The chemical composition of the high-entropy alloy oxide composite material is CeNiFeCuCoOx-SiWA, wherein the value range of x is 5 to 7.5, and SiWA is silicotungstic acid.

[0009] One technical solution in the technical solution of the present invention regarding the high-entropy alloy oxide composite material has at least the following

[0010] Beneficial effects:

[0011] The high-entropy alloy oxide composite material of the present invention has the feasibility of low-temperature synthesis. Traditional high-entropy alloy oxides require high-temperature sintering (600 - 1600 °C), while the introduction of silicotungstic acid (SiWA) may reduce the activation energy for the formation of the high-entropy phase through the template effect or catalytic action of its cluster structure, realizing low-temperature or medium-temperature synthesis, and significantly reducing energy consumption and production costs. The multi-components of the high-entropy alloy are prone to element segregation during the cycling process. The uniform dispersion of SiWA may fix metal sites through interfacial interactions (such as metal-oxygen-tungsten bonding), maintain a homogeneous single-phase structure, and delay phase separation, thereby improving the long-cycle stability.

[0012] For the high-entropy alloy oxide composite material of the present invention, after the assembly of cerium nickel iron copper cobalt oxide and silicotungstic acid, silicotungstic acid can promote the formation of the high-entropy alloy oxide, endowing it with a higher specific capacity, and inhibiting the huge stress during charge / discharge, reducing volume change, thereby improving the cycle stability of the high-entropy alloy oxide and enabling the lithium-ion battery to have a longer lifespan.

[0013] Silicotungstic acid is a cluster molecule with a good electron-donating effect. When assembled with the cerium nickel iron copper cobalt high-entropy alloy oxide, it can serve as a bridge for electron transfer to improve the conductivity of the cerium nickel iron copper cobalt high-entropy alloy oxide, effectively enhancing the charge transfer rate during charge / discharge and improving the battery performance.

[0014] CeNiFeCuCoO xMultiple metal components (such as the redox activity of Cu / Co, the catalysis of Fe / Ni, and the oxygen vacancy regulation of Ce) and the heteropolyanions of SiWA may form hierarchical lithium storage sites to achieve co - transport of electrons / ions, further enhancing the specific capacity (possibly breaking through the theoretical limit of single oxides). The rigid cluster structure of SiWA can act as a nanoscale "scaffold" to absorb the local stress of high - entropy oxides through elastic deformation during charge and discharge processes, inhibit crack propagation, and relieve volume expansion. SiWA may decompose at the electrode / electrolyte interface to form a solid electrolyte interface (SEI) film rich in WO3 or Li2SiO3. This film has both high ionic conductivity and mechanical toughness, reducing side reactions and lithium dendrite growth, and improving the Coulomb efficiency.

[0015] The introduction of SiWA can improve the film - forming property of the composite material, enabling it to be directly coated on the current collector without an additional binder (such as PVDF), simplifying the electrode process and increasing the loading of active materials. The "cocktail effect" of high - entropy components and the thermal stability of SiWA may endow the composite material with a performance retention rate at extreme temperatures (-20 to 60 °C), which is superior to that of traditional graphite or silicon - based anodes. Cerium (Ce), as a rare earth element with a relatively high abundance, partially replacing cobalt (Co) can reduce the material cost and toxicity, while the non - toxic property of SiWA conforms to the development trend of green batteries.

[0016] The oxygen - rich surface of SiWA may provide a fast migration path for lithium ions, while the metal components of high - entropy oxides form an electron - conducting network to achieve "bicontinuous" conduction and reduce polarization. The dynamic lattice reconstruction ability of high - entropy oxides and the flexibility of SiWA can cooperate to repair micro - damages during cycling and extend the service life of the material.

[0017] Experimental results show that the assembly of cerium - nickel - iron - copper - cobalt high - entropy alloy oxide and silicotungstic acid used as the anode material for lithium - ion batteries has good cycle stability and rate performance.

[0018] According to some embodiments of the present invention, the value range of x is 5.5 to 7.

[0019] According to some embodiments of the present invention, in the high - entropy alloy oxide composite material, the molar ratio of CeNiFeCuCoOx to SiWA is 1:1 to 2.

[0020] According to some embodiments of the present invention, in the high - entropy alloy oxide composite material, the molar ratio of CeNiFeCuCoOx to SiWA is 1:1.4 to 1.9.

[0021] The second aspect of the present invention provides a method for preparing the high-entropy alloy oxide composite material of the first aspect of the present invention, comprising the following steps: preparing metal sources according to the chemical composition, and adding the metal sources and silicotungstic acid into a reaction system for reaction, wherein the reaction system comprises a poor solvent, a good solvent and a surfactant.

[0022] One technical solution in the method for preparing the high-entropy alloy oxide composite material of the present invention has at least the following

[0023] Beneficial effects:

[0024] The preparation method of the present invention belongs to the one-pot method, which does not require expensive equipment and complex process control, has mild reaction conditions, easily available raw materials, low production cost, and is easy to industrialize.

[0025] There are a large number of nucleophilic oxygen atoms on silicotungstic acid, which can combine with metal ions in a covalent or non-covalent manner, thereby forming a high-entropy alloy oxide with high activity and stability.

[0026] The poor solvent and the good solvent are two solvents with large polarity differences.

[0027] The volume ratio of the poor solvent to the good solvent is 2-4:1.

[0028] The volume ratio of the poor solvent to the good solvent is 3:1.

[0029] In the preparation method of the present invention, under the combined action of two solvents with large polarity differences and a surfactant, a variety of metal sources generate cerium-nickel-iron-copper-cobalt high-entropy oxides through a solvothermal reaction. When silicotungstic acid and a variety of metal salts are simultaneously added into the reaction system, an assembly of the cerium-nickel-iron-copper-cobalt high-entropy alloy oxide and silicotungstic acid forms a high-entropy alloy oxide composite material.

[0030] According to some embodiments of the present invention, the morphology of the high-entropy alloy oxide composite material is nanospheres.

[0031] Elements such as cerium, nickel, iron, copper, cobalt, silicon, tungsten and oxygen are uniformly distributed on the nanospheres, and no obvious phase separation occurs.

[0032] The nanospheres are formed by the "cluster-nucleus" co-assembly strategy.

[0033] "Cluster-nucleus" co-assembly means introducing polyoxometalate clusters (such as silicotungstic acid) with sizes equivalent to those of nuclei (metal oxides) and with definite sizes and structures into the synthesis reaction system to intervene in the nucleation of the material. Then, the clusters and the nuclei co-assemble through interactions (non-covalent ways such as van der Waals forces) to form a cluster-nucleus co-assembly.

[0034] According to some embodiments of the present invention, the particle size of the nanospheres is 400 nm to 800 nm.

[0035] According to some embodiments of the present invention, the particle size of the nanospheres is 500 nm to 700 nm.

[0036] According to some embodiments of the present invention, the particle size of the nanospheres is about 600 nm.

[0037] According to some embodiments of the present invention, the metal source includes a cerium source, a nickel source, an iron source, a copper source, and a cobalt source.

[0038] According to some embodiments of the present invention, the cerium source includes ammonium cerium nitrate.

[0039] According to some embodiments of the present invention, the nickel source includes nickel chloride hexahydrate.

[0040] According to some embodiments of the present invention, the iron source includes iron chloride hexahydrate.

[0041] According to some embodiments of the present invention, the copper source includes copper nitrate trihydrate.

[0042] According to some embodiments of the present invention, the cobalt source includes cobalt acetate tetrahydrate.

[0043] According to some embodiments of the present invention, the poor solvent includes absolute ethanol and absolute methanol.

[0044] According to some embodiments of the present invention, the good solvent includes cyclohexane and n-hexane.

[0045] According to some embodiments of the present invention, the surfactant includes at least one of octadecyltrimethylammonium chloride, octadecylamine, and octadecenylamine.

[0046] According to some embodiments of the present invention, the surfactant includes octadecenylamine.

[0047] According to some embodiments of the present invention, it includes the following steps:

[0048] S1: Add the metal source and silicotungstic acid to the poor solvent. After dissolution, add the good solvent and the surfactant, and carry out the reaction in a high-pressure reaction kettle;

[0049] S2: Centrifuge and dry the product of step S1 to obtain the high-entropy alloy oxide composite material.

[0050] According to some embodiments of the present invention, the temperature of the reaction is 140 °C to 200 °C.

[0051] According to some embodiments of the present invention, the temperature of the reaction is any value among 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C or a range value formed by any two of them, such as 160°C to 180°C.

[0052] According to some embodiments of the present invention, the time of the reaction is 8h to 20h.

[0053] According to some embodiments of the present invention, the time of the reaction is any value among 8h, 10h, 12h, 14h, 16h, 18h or a range value formed by any two of them, such as 10h to 12h.

[0054] According to some embodiments of the present invention, the preparation method may be:

[0055] Step 1: According to the chemical composition, dissolve the metal source and silicotungstic acid together in 9 mL of a poor solvent, stir for 5 min, then add 27 mL of n - hexane, and then add 9 mL of octadeceneamine, continue to stir for 30 min, then transfer the solution to a 50 - mL autoclave, place the autoclave in a blast drying oven, and take the solution after reacting at 160°C for 8 - 12 h;

[0056] Step 2: Take out the solution after the reaction is completed and put it into a centrifuge tube, use a high - speed centrifuge to obtain a solid product, then wash the obtained solid product three times, put it into a blast drying oven, and dry for 8 - 12 h to obtain an assembly of cerium - nickel - iron - copper - cobalt high - entropy alloy oxide and silicotungstic acid.

[0057] In Step 1, the stirring temperature may be 20°C to 25°C.

[0058] In Step 2, the drying temperature may also be 60°C to 80°C.

[0059] In Step 2, the centrifugation speed may be 8000 - 10000 rpm.

[0060] The solvent used for washing in Step 2 is anhydrous ethanol.

[0061] The third aspect of the present invention provides a negative electrode material for a lithium - ion battery, including the high - entropy alloy oxide composite material of the first aspect of the present invention or the high - entropy alloy oxide composite material prepared by the method of the second aspect of the present invention.

[0062] For the negative electrode material of the lithium - ion battery of the present invention, after the cerium - nickel - iron - copper - cobalt oxide and silicotungstic acid are assembled, silicotungstic acid can promote the formation of the high - entropy alloy oxide, making it have a higher specific capacity, and inhibit the huge stress during the charge / discharge process, reduce the volume change, thereby improving the cycle stability of the high - entropy alloy oxide and enabling the lithium - ion battery to have a longer lifespan.

[0063] Silicotungstic acid is a cluster molecule with good electron-donating effect. After being assembled with cerium-nickel-iron-copper-cobalt high-entropy alloy oxide, it can serve as a bridge for electron transfer to improve the conductivity of cerium-nickel-iron-copper-cobalt high-entropy alloy oxide, effectively enhancing the charge transfer rate during charge / discharge and improving the battery performance.

[0064] The experimental results show that the assembly of cerium-nickel-iron-copper-cobalt high-entropy alloy oxide and silicotungstic acid used as the anode material for lithium-ion batteries has good cycle stability and rate performance.

[0065] The fourth aspect of the present invention provides a lithium-ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode is prepared from the anode material for lithium-ion battery of the present invention.

[0066] The lithium-ion battery of the present invention has good electrochemical performance and cycle stability.

[0067] According to some embodiments of the present invention, the negative electrode further includes a conductive agent and a binder, and the mass ratio of the anode material, the conductive agent, and the binder is 7:2:1 or 8:1:1. Description of the Drawings

[0068] Figure 1 are the TEM and EDX images of the high-entropy alloy oxide composite material prepared in Example 1 of the present invention.

[0069] Figure 2 are the TEM and EDX images of the high-entropy alloy oxide composite material prepared in Comparative Example 1 of the present invention.

[0070] Figure 3 is the charge-discharge curve of Example 1 of the present invention as the anode of a lithium-ion battery.

[0071] Figure 4 is the cycle performance test chart of Example 1 of the present invention as the anode of a lithium-ion battery.

[0072] Figure 5 is the cycle performance test chart of Comparative Example 1 of the present invention as the anode of a lithium-ion battery.

[0073] Figure 6 is the cycle performance test chart of Comparative Example 2 of the present invention as the anode of a lithium-ion battery.

[0074] Figure 7 is the rate performance test chart of Example 1, Comparative Example 1, and Comparative Example 2 of the present invention as the anode of a lithium-ion battery. Detailed Embodiments

[0075] The concept of the present invention and the technical effects produced will be clearly and completely described below in conjunction with embodiments to fully understand the purpose, features, and effects of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative efforts shall fall within the scope of protection of the present invention.

[0076] In the description of the present invention, the description with reference to terms such as "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0077] Unless otherwise specified, "room temperature" in the present invention means 25°C ± 5°C.

[0078] Unless otherwise specified, "about" in the present invention means that the allowable error is within ±2%.

[0079] For those conditions not specified in the embodiments, they are carried out according to conventional conditions or the conditions recommended by the manufacturer. For reagents or instruments whose manufacturers are not specified, they are all conventional products that can be obtained through commercial purchase.

[0080] It should be noted that because there are many types of metals and the synthesized metal oxides will not be pure phases and there are oxygen vacancies, the actual number of O atoms is difficult to determine. Therefore, x is usually used to represent the number of oxygen atoms. Theoretically, the value range of x is 5 - 7.5.

[0081] Example 1

[0082] In this example, a high-entropy alloy oxide composite material was first prepared and then used to prepare a negative electrode. The specific steps are as follows:

[0083] (1) Preparation method of the assembly material of cerium-nickel-iron-copper-cobalt high-entropy alloy oxide and silicotungstic acid

[0084] Step 1: Dissolve 0.40 mmol of ammonium cerium(IV) nitrate, 0.27 mmol of nickel(II) chloride hexahydrate, 0.33 mmol of iron(III) chloride hexahydrate, 0.27 mmol of copper(II) nitrate trihydrate, 0.26 mmol of cobalt(II) acetate tetrahydrate and 0.22 mmol of silicotungstic acid hydrate in 9 mL of absolute ethanol, stir for 5 min. After complete dissolution, add 27 mL of cyclohexane and 9 mL of octadecyltrimethylammonium chloride, continue stirring for 30 min, then transfer to a high-pressure reactor. Then place the reactor in a forced-air drying oven and react at 160 °C for 10 h;

[0085] Step 2: Take out the solution after the reaction is completed and put it into a centrifuge tube. Centrifuge at a speed of 10000 rpm for 10 min using a high-speed centrifuge to obtain a solid sample. Then wash the obtained product three times with absolute ethanol and place it in a forced-air drying oven to dry at 60 °C for 12 h to obtain an assembly of cerium nickel iron copper cobalt high-entropy alloy oxide and silicotungstic acid (CeNiFeCuCoO x -SiWA);

[0086] (2) Preparation method of the negative electrode of the assembly of cerium nickel iron copper cobalt high-entropy alloy oxide and silicotungstic acid

[0087] Use the CeNiFeCuCoO x -SiWA composite material prepared in (1) as the negative electrode active material of the lithium-ion battery, acetylene black as the conductive agent, polyvinylidene fluoride as the binder, and N-methylpyrrolidone as the solvent. Mix them in a mass ratio of active material:conductive agent:binder of 7:2:1, and then stir for 6 hours to form a uniform slurry. Then scrape off the slurry and coat it on a clean copper foil. Place it in a vacuum oven and dry at 120 °C for 12 h, and then cut it into circular pieces with a diameter of 12 mm.

[0088] Example 2

[0089] In this example, a high-entropy alloy oxide composite material was first prepared and then made into a negative electrode. The specific steps are as follows:

[0090] (1) Preparation method of the assembly material of cerium nickel iron copper cobalt high-entropy alloy oxide and silicotungstic acid

[0091] Step 1: Dissolve 0.40 mmol of ammonium cerium(IV) nitrate, 0.27 mmol of nickel(II) chloride hexahydrate, 0.33 mmol of iron(III) chloride hexahydrate, 0.27 mmol of copper(II) nitrate trihydrate, 0.26 mmol of cobalt(II) acetate tetrahydrate and 0.22 mmol of silicotungstic acid hydrate in 9 mL of absolute methanol, stir for 5 min. After complete dissolution, add 27 mL of cyclohexane and 9 mL of oleylamine, continue stirring for 30 min, then transfer to a high-pressure reactor. Then place the reactor in a forced-air drying oven and react at 160 °C for 12 h;

[0092] Step 2: Take out the solution after the reaction is completed and put it into a centrifuge tube. Use a high-speed centrifuge to centrifuge at a speed of 10,000 rpm for 10 min to obtain a solid sample. Then wash the obtained product three times with absolute ethanol and place it in a forced-air drying oven to dry at 60 °C for 12 h to obtain an assembly of cerium nickel iron copper cobalt high-entropy alloy oxide and silicotungstic acid (CeNiFeCuCoO x -SiWA);

[0093] (2) Preparation method of the negative electrode of the assembly of cerium nickel iron copper cobalt high-entropy alloy oxide and silicotungstic acid

[0094] Use the CeNiFeCuCoO x -SiWA composite material prepared in (1) as the negative electrode active material of the lithium-ion battery, acetylene black as the conductive agent, polyvinylidene fluoride as the binder, and N-methylpyrrolidone as the solvent. Mix them in a mass ratio of active material: conductive agent: binder of 7:2:1, and then stir for 6 hours to form a uniform slurry. Then scrape off the slurry and coat it on a clean copper foil. Place it in a vacuum oven and dry at 120 °C for 12 h, and then cut it into circular pieces with a diameter of 12 mm.

[0095] Example 3

[0096] In this example, a high-entropy alloy oxide composite material was first prepared and then made into a negative electrode. The specific steps are as follows:

[0097] (1) Preparation method of the assembly material of cerium nickel iron copper cobalt high-entropy alloy oxide and silicotungstic acid

[0098] Step 1: Take 0.40 mmol of ammonium cerium nitrate, 0.27 mmol of nickel chloride hexahydrate, 0.33 mmol of iron chloride hexahydrate, 0.27 mmol of copper nitrate trihydrate, 0.26 mmol of cobalt acetate tetrahydrate, and 0.22 mmol of silicotungstic acid hydrate and dissolve them in 9 mL of absolute ethanol. Stir for 5 min. After complete dissolution, add 27 mL of n-hexane and 9 mL of octadeceneamine, continue to stir for 30 min, and then transfer to a high-pressure reaction kettle. Then place the reaction kettle in a forced-air drying oven and react at 160 °C for 12 h;

[0099] Step 2: Take out the solution after the reaction is completed and put it into a centrifuge tube. Use a high-speed centrifuge to centrifuge at a speed of 10,000 rpm for 10 min to obtain a solid sample. Then wash the obtained product three times with absolute ethanol and place it in a forced-air drying oven to dry at 60 °C for 12 h to obtain an assembly of cerium nickel iron copper cobalt high-entropy alloy oxide and silicotungstic acid (CeNiFeCuCoO x -SiWA);

[0100] (2) Preparation method of the negative electrode of the assembly of cerium nickel iron copper cobalt high-entropy alloy oxide and silicotungstic acid

[0101] Using the CeNiFeCuCoO prepared in (1) x -SiWA composite material as the negative electrode active material for lithium-ion batteries, acetylene black as the conductive agent, polyvinylidene fluoride as the binder, and N-methylpyrrolidone as the solvent. Mix the active material, conductive agent, and binder in a mass ratio of 7:2:1, and then stir for 6 hours to form a uniform slurry. Then scrape the slurry and coat it on a clean copper foil. Place it in a vacuum oven and dry it at 120 °C for 12 h, and then cut it into discs with a diameter of 12 mm.

[0102] Example 4

[0103] In this example, a high-entropy alloy oxide composite material was first prepared and then used to prepare the negative electrode. The specific steps are as follows:

[0104] (1) Preparation method of the assembled material of cerium nickel iron copper cobalt high-entropy alloy oxide and silicotungstic acid

[0105] Step 1: Dissolve 0.40 mmol of ammonium cerium nitrate, 0.27 mmol of nickel chloride hexahydrate, 0.33 mmol of iron chloride hexahydrate, 0.27 mmol of copper nitrate trihydrate, 0.26 mmol of cobalt acetate tetrahydrate, and 0.22 mmol of silicotungstic acid hydrate in 9 mL of anhydrous methanol, stir for 5 min. After complete dissolution, add 27 mL of cyclohexane and 9 mL of octadecylamine, continue to stir for 30 min, and then transfer to a high-pressure reaction kettle. Then place the reaction kettle in a forced-air drying oven and react at 160 °C for 12 h;

[0106] Step 2: Take out the reacted solution and put it into a centrifuge tube. Use a high-speed centrifuge to centrifuge at a speed of 10000 rpm for 10 min to obtain a solid sample. Then wash the obtained product three times with anhydrous ethanol and place it in a forced-air drying oven to dry at 60 °C for 12 h to obtain the assembled body of cerium nickel iron copper cobalt high-entropy alloy oxide and silicotungstic acid (CeNiFeCuCoO x -SiWA);

[0107] (2) Preparation method of the negative electrode of the assembled body of cerium nickel iron copper cobalt high-entropy alloy oxide and silicotungstic acid

[0108] Using the CeNiFeCuCoO prepared in (1) x -SiWA composite material as the negative electrode active material for lithium-ion batteries, acetylene black as the conductive agent, polyvinylidene fluoride as the binder, and N-methylpyrrolidone as the solvent. Mix the active material, conductive agent, and binder in a mass ratio of 8:1:1, and then stir for 6 hours to form a uniform slurry. Then scrape the slurry and coat it on a clean copper foil. Place it in a vacuum oven and dry it at 120 °C for 12 h, and then cut it into discs with a diameter of 12 mm.

[0109] Comparative Example 1

[0110] The difference between this comparative example and Example 1 is that the material does not contain silicotungstic acid. The specific preparation steps are as follows:

[0111] (1) A preparation method of a cerium-nickel-iron-copper-cobalt oxide negative electrode material

[0112] Step 1: Take 0.40 mmol of ammonium cerium nitrate, 0.27 mmol of nickel chloride hexahydrate, 0.33 mmol of iron chloride hexahydrate, 0.27 mmol of copper nitrate trihydrate, and 0.26 mmol of cobalt acetate tetrahydrate hydrate and dissolve them in 9 mL of absolute ethanol. Stir for 5 min. After complete dissolution, add 27 mL of n-hexane and 9 mL of octadeceneamine, and continue to stir for 30 min. Then transfer it to a high-pressure reaction kettle, and then place the reaction kettle in a blast drying oven and react at 160 °C for 12 h;

[0113] Step 2: Take out the solution after the reaction is completed and put it into a centrifuge tube. Use a high-speed centrifuge to centrifuge at a speed of 10,000 rpm for 10 min to obtain a solid sample. Then wash the obtained product three times with absolute ethanol and place it in a blast drying oven to dry at 60 °C for 12 h to obtain an assembly of cerium-nickel-iron-copper-cobalt high-entropy alloy oxide and silicotungstic acid (CeNiFeCuCoO x );

[0114] (2) A preparation method of a cerium-nickel-iron-copper-cobalt oxide lithium-ion battery negative electrode

[0115] Use the CeNiFeCuCoO prepared in (1) x The material is used as the negative electrode active material of the lithium-ion battery, acetylene black is used as the conductive agent, polyvinylidene fluoride is used as the binder, and N-methylpyrrolidone is used as the solvent. Mix evenly at a mass ratio of active material: conductive agent: binder of 7:2:1, and then stir for 6 hours to form a uniform slurry. Then scrape off the slurry and coat it on a clean copper foil. Place it in a vacuum oven and dry at 120 °C for 12 h, and then cut it into circular pieces with a diameter of 12 mm.

[0116] Comparative Example 2

[0117] The difference between this comparative example and Example 1 is that the material does not contain cerium-nickel-iron-copper-cobalt oxide. The specific preparation steps are as follows:

[0118] Use commercial silicotungstic acid hydrate as the negative electrode active material of the lithium-ion battery, acetylene black as the conductive agent, polyvinylidene fluoride as the binder, and N-methylpyrrolidone as the solvent. Mix at a mass ratio of active material: conductive agent: binder of 7:2:1, and then stir for 6 hours to form a uniform slurry. Then scrape off the slurry and coat it on a clean copper foil. Place it in a vacuum oven and dry at 120 °C for 12 h, and then cut it into circular pieces with a diameter of 12 mm.

[0119] Comparative Example 3

[0120] The difference from Example 1 is that two solvents with large polarity differences were not used, and only 36 mL of n-hexane was used. The synthesized sample was not completely dissolved and there were still some metal salts left.

[0121] Comparative Example 4

[0122] The difference from Example 1 is that two solvents with large polarity differences were not used, and only 36 mL of absolute ethanol was used. Tests found that the prepared sample had heterophase and poor performance.

[0123] Comparative Example 5

[0124] The difference from Example 1 is that 18 mL of the surfactant octadeceneamine was not added. Tests found that the prepared sample had heterophase, large particles, and poor performance.

[0125] Preparation method of lithium-ion battery

[0126] Using the prepared negative electrode sheet as the working electrode, glass fiber (Whatman GF / F) as the separator, and lithium sheet as the counter electrode, ethylene carbonate and dimethyl carbonate with a volume ratio of 1:1 were used as solvents to prepare a 1 mol L -1 LiPF6 as the electrolyte. In a glove box filled with an argon atmosphere, a 2032-type button battery was assembled, placed in a constant temperature drying oven at 25 °C and left to stand for 10 h before electrochemical performance testing.

[0127] Electrochemical performance testing method

[0128] Electrochemical performance tests were all carried out in a constant temperature oven at 25 °C. Charge / discharge tests were carried out on a LAND CT2001A instrument (note: reverse polarity, first discharge and then charge), and the constant current voltage cut-off values were 0.01 V and 3 V respectively.

[0129] Test example

[0130] In this test example, a transmission electron microscope test was carried out on the assembly material of the cerium nickel iron copper cobalt high-entropy alloy oxide and silicotungstic acid of Example 1, and the test results are as Figure 1 shown.

[0131] The basic morphology of the assembly of cerium nickel iron copper cobalt high-entropy alloy oxide and silicotungstic acid is nanospheres with a particle size of about 600 nm. The cerium nickel iron copper cobalt silicon tungsten oxygen elements are evenly distributed on it, and no obvious phase separation occurs.

[0132] In this test example, a transmission electron microscope test was carried out on the cerium nickel iron copper cobalt oxide material of Comparative Example 1, and the test results are as Figure 2 shown.

[0133] The basic morphology of the assembly of cerium-nickel-iron-copper-cobalt high-entropy alloy oxide and silicotungstic acid is a block with a particle size of about 2 μm to 3 μm. The distribution of cerium, nickel, iron, copper, and cobalt oxygen elements on it is uneven, and obvious phase separation occurs.

[0134] In this test example, the constant current charge / discharge performance of the negative electrode materials of Example 1, Comparative Example 1, and Comparative Example 2 was tested, and the test results are as Figure 3 , Figure 4 , Figure 5 , Figure 6 and Figure 7 shown.

[0135] It can be seen from Figure 3 that the initial discharge specific capacity of the material provided in Example 1 reached 1338.8 mAh·g -1 . From the fifth cycle to the one-hundredth cycle, the charge / discharge capacities of the charge / discharge curves are almost the same, indicating that the negative electrode material of the assembly of cerium-nickel-iron-copper-cobalt high-entropy alloy oxide and silicotungstic acid has good cycle stability.

[0136] It can be seen from Figure 4 that when Example 1 is cycled to the one-hundredth cycle, the specific capacity is still 729.9 mAh g -1 , and the Coulomb efficiency is 98.75%, indicating less energy loss.

[0137] It can be seen from Figure 5 that the initial discharge specific capacity of the negative electrode material provided in Comparative Example 1 is 1198.9 mAh g -1 . The discharge specific capacity continuously decays, and the stability is poor. When cycled to the one-hundredth cycle, the specific capacity is only 70.7 mAh g -1 , while the Coulomb efficiency is 97.23%, and the energy loss is much higher than that of the negative electrode material of Example 1.

[0138] As Figure 6 shown, the initial discharge specific capacity of the negative electrode material provided in Comparative Example 2 is 161.8 mAh·g -1 . The discharge specific capacity continuously increases, and the stability is good. When cycled to the one-hundredth cycle, the specific capacity is 73.1 mAh·g -1 , while the Coulomb efficiency is 98.18%, indicating that silicotungstic acid can continuously improve the performance of lithium-ion batteries.

[0139] The negative electrode material provided by Comparative Example 3 has poor performance because the metal precursor cannot be completely dissolved.

[0140] The negative electrode material provided by Comparative Example 4 has poor performance because the synthesized sample has a heterogeneous phase.

[0141] The negative electrode material provided by Comparative Example 5 has poor performance because of the heterogeneous phase and large particles.

[0142] The rate performance tests of the negative electrode materials of Example 1, Comparative Example 1 and Comparative Example 2 were also carried out. As Figure 7 shown, at current densities of 0.1, 0.2, 0.5, 1 and 2 Ag -1 , the specific capacities corresponding to Example 1 were 713.2, 628.2, 500.6, 405.6 and 304.3 mAh·g -1 , respectively, and when the current density returned to 0.1 Ag -1 , the value of the specific capacity was close to the initial value, indicating that the assembly of cerium nickel iron copper cobalt high-entropy alloy oxide and silicotungstic acid had excellent rate performance; while for the negative electrode material of Comparative Example 1 at 0.1, 0.2, 0.5, 1 and 2 Ag -1 , the corresponding specific capacities were 319.0, 209.9, 120.1, 60.6 and 13.4 mAh·g -1 , respectively, and when the current density returned to 0.1 Ag -1 , the specific capacity continued to decay, that is, the electron transport ability of the negative electrode material of Comparative Example 1 was poor and the rate performance was not good, which indicated that if there was no assembly with silicotungstic acid, the performance of the lithium-ion battery formed by cerium nickel iron copper cobalt oxide was poor; in addition, for the negative electrode material of Comparative Example 2 at 0.1, 0.2, 0.5, 1 and 2 Ag -1 , the corresponding specific capacities were 53.4, 43.9, 34.9, 29.4 and 25.7 mAh·g -1 , respectively, and when the current density returned to 0.1 A·g -1 , the specific capacity was still increasing and the rate performance was excellent, which could also illustrate the important role played by silicotungstic acid.

[0143] The present invention has been described in detail above in conjunction with the embodiments, but the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the gist of the present invention.

[0144] The present invention has been described in detail above in conjunction with the embodiments, but the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the gist of the present invention.

Claims

1. A high-entropy alloy oxide composite material, characterized in that, The chemical composition of the high-entropy alloy oxide composite material is CeNiFeCuCoOx-SiWA, where the value range of x is 5 to 7.5, and SiWA is silicotungstic acid.

2. A method for preparing the high-entropy alloy oxide composite material as described in claim 1, characterized in that, It includes the following steps: Prepare metal sources according to the chemical composition, add the metal sources and silicotungstic acid into a reaction system for reaction, and the reaction system includes a poor solvent, a good solvent and a surfactant.

3. The method according to claim 2, wherein The metal sources include a cerium source, a nickel source, an iron source, a copper source and a cobalt source.

4. The method according to claim 3, wherein The cerium source includes ammonium cerium nitrate; and / or, the nickel source includes nickel chloride hexahydrate; and / or, the iron source includes ferric chloride hexahydrate; and / or, the copper source includes copper nitrate trihydrate; and / or, the cobalt source includes cobalt acetate tetrahydrate.

5. The method according to claim 2, wherein The poor solvent includes absolute ethanol and absolute methanol.

6. The method according to claim 2, characterized in that, The good solvent includes cyclohexane and n-hexane.

7. The method according to claim 2, wherein The surfactant includes at least one of octadecyl trimethyl ammonium chloride, octadecylamine and octadecenylamine.

8. The method according to any one of claims 2 to 7, characterized in that, It includes the following steps: S1: Add the metal sources and silicotungstic acid into the poor solvent, after dissolution, add the good solvent and the surfactant, and conduct the reaction in a high-pressure reaction kettle; S2: Centrifuge and dry the product of step S1 to obtain the high-entropy alloy oxide composite material.

9. The method according to claim 8, wherein The temperature of the reaction is 140°C to 200°C; and / or, the reaction time is 8h to 20h.

10. A negative electrode material for a lithium-ion battery, characterized in that, It includes the high-entropy alloy oxide composite material described in claim 1 or the high-entropy alloy oxide composite material prepared by the method described in any one of claims 2 to 9.

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