Nano core-shell structure high-entropy oxide and low-temperature preparation method and application thereof

Abstract

The invention discloses a nano core-shell structure high-entropy oxide and a low-temperature preparation method and application thereof, and belongs to the technical field of high-entropy materials and lithium ion battery energy storage. An iron source, a cobalt source, a nickel source, a chromium source and a manganese source are used as reaction materials, glycerol is used as a surfactant, and the high-entropy oxide with the nano core-shell structure is synthesized by adopting a solvothermal method and a low-temperature preparation process. The preparation method is simple in process, low in cost and good in repeatability, and the prepared high-entropy oxide with the nano core-shell structure is high in purity. When the nano core-shell structure high-entropy oxide is used as a lithium ion battery negative electrode material, the nano core-shell structure high-entropy oxide shows extremely high lithium storage specific capacity and excellent cycle stability, the first discharge specific capacity reaches up to 1488.3 mA h / g under the current density of 0.1 A / g, and the capacity is still maintained at about 1174.15 mA h / g after 50 cycles.

Description

Technical Field

[0001] The present invention belongs to the technical fields of high-entropy materials and lithium-ion battery energy storage technology, and particularly relates to a nano core-shell structure high-entropy oxide, a low-temperature preparation method thereof, and an application thereof. Background Art

[0002] Lithium-ion batteries have the advantages of small volume, high energy density, light weight, and long cycle life, and have been widely used in fields such as portable electronic products, power tools, and electric vehicles. In recent years, transition metal oxides have received attention as anode materials for lithium-ion batteries. Since high-entropy materials based on transition metals were first reported in 2015, they have attracted many researchers due to the novel "high-entropy effect" they exhibit and the excellent mechanical, electrical, thermal, and other properties of the materials themselves. There are currently four types of existing high-entropy oxides (HEO) with rock salt structure, fluorite structure, calcium titanate structure, and spinel structure. Due to their different structures, their respective characteristics are different, and their application ranges are relatively wide. High-entropy oxides are entropy-stable crystal structures with five or more metal elements, and the elements contained must be in equimolar or near-equimolar ratios and evenly distributed to ensure the maximum configurational entropy of the system.

[0003] High-entropy oxides have good lithium-ion storage performance due to the entropy stabilization effect and are considered promising electrode materials for lithium-ion batteries. Currently, the preparation methods of high-entropy oxides mainly include solid-phase method, pyrolysis method, hydrothermal synthesis method, co-precipitation method, and liquid-phase combustion synthesis method. Chinese Patent 202010162801.3 uses Fe2O3, Co2O3, Cr2O3, MnO2, and ZnO powders with a molar ratio of 1:1:1:2:2, ball-milling and mixing them, then heating to 800-1000 °C and calcining for 1-3 hours, and then cooling to room temperature with the furnace to obtain (FeCoCrMnZn)3O4 high-entropy oxide powder with a single spinel structure. Jia-Zheng Yen et al. synthesized HEO using hydrothermal method and heat treatment with equimolar Co(NO3)2, Mg(NO3)2, Cu(NO3)2, Zn(NO3)2, and Ni(NO3)2 (Yen J Z, Yang Y C, Tuan H Y. Interface engineering of high entropy Oxide@Polyaniline heterojunction enables highly stable and excellent lithium ion storage performance[J]. Chemical Engineering Journal, 2022, 450:137924.). The above reports prove that different high-entropy oxides have wide applications in various research fields. However, since most preparation processes are relatively complex or involve high reaction temperatures, it will lead to larger particle sizes of HEO, thereby affecting battery performance.

[0004] Aiming at the technical problems existing in the existing high-entropy oxides, such as relatively complex preparation processes, high reaction temperatures, resulting in larger particle sizes of high-entropy oxides, and thus affecting battery performance, it is urgent to find a new high-entropy oxide and its preparation method to simplify the preparation process of high-entropy oxides, reduce the reaction temperature, and thereby improve battery performance. Summary of the Invention

[0005] In order to overcome the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide a high-entropy oxide with a nano-core-shell structure, its low-temperature preparation method and application, so as to solve the technical problems existing in the existing high-entropy oxides, such as relatively complex preparation processes, high reaction temperatures, resulting in larger particle sizes of high-entropy oxides, and thus affecting battery performance.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] The present invention discloses a low-temperature preparation method of a high-entropy oxide with a nano-core-shell structure, including:

[0008] First, add iron source, cobalt source, nickel source, chromium source and manganese source into the mixed solution composed of glycerol and isopropanol, and stir evenly; then, through solvothermal reaction, washing and drying, and calcination, the nano core-shell structured high-entropy oxide is obtained.

[0009] Preferably, the dosage ratio of iron source:cobalt source:nickel source:chromium source:manganese source:glycerol:isopropanol is (0.1 - 0.15) mmol:(0.1 - 0.15) mmol:(0.1 - 0.15) mmol:(0.1 - 0.15) mmol:(0.1 - 0.15) mmol:(5 - 10) mL:(55 - 65) mL.

[0010] Preferably, the temperature of the solvothermal reaction is 150 - 200 °C; the time of the solvothermal reaction is 8 - 24 h.

[0011] Preferably, the temperature of the calcination is 400 - 600 °C; the time of the calcination is 2 - 4 h.

[0012] Preferably, the heating rate of the calcination is 2 - 10 °C / min.

[0013] Preferably, the iron source is Fe(NO3)3, Fe2(SO4)3, FeCl3 or Fe(OH)(CH3COO)2; the cobalt source is Co(NO3)2, CoSO4, CoCl2 or (CH3COO)2Co; the nickel source is NiCl2, NiSO4, Ni(NO3)2 or Ni(CH3COO)2; the chromium source is Cr(NO3)3, Cr2(SO4)3, CrCl3 or (CH3COO)3Cr; the manganese source is Mn(NO3)2, MnSO4, MnCl2 or (CH3COO)2Mn.

[0014] Preferably, the stirring time is 1 - 3 h.

[0015] Preferably, the washing condition is to wash 2 - 5 times with absolute ethanol during centrifugation.

[0016] The present invention also discloses the nano core-shell structured high-entropy oxide prepared by the above preparation method.

[0017] The present invention also discloses the application of the above nano core-shell structured high-entropy oxide in the preparation of the anode material for lithium-ion batteries.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention discloses a low-temperature preparation method of a nano core-shell structured high-entropy oxide. Using iron source, cobalt source, nickel source, chromium source and manganese source as reaction raw materials, and glycerol as a surfactant, the nano core-shell structured high-entropy oxide is obtained by assisting the solvothermal method and the low-temperature preparation process; this preparation method has the advantages of simple process, low cost, good repeatability and high product purity. The commonly used solid-phase reaction method has the characteristics of long heat preservation time, high reaction temperature involved, complex process and long cycle; in addition, the preparation of high-entropy oxides by the wet chemical method has the characteristics of high raw material cost, many preparation steps and uncontrollable process. The present invention solves the technical problems existing in the existing high-entropy oxides, such as relatively complex preparation process, high reaction temperature involved, resulting in larger particle size of high-entropy oxide particles, and thus affecting the battery performance.

[0020] The present invention also discloses the nano core-shell structured high-entropy oxide prepared by the above preparation method. The nano core-shell structured high-entropy oxide has a typical spherical morphology, and the size is uniform, with a particle size of 500-700 nm. As the annealing temperature gradually increases, the inside of the nano-sphere begins to shrink, and a void is formed between the inner core and the outer shell, and finally the nano core-shell structured high-entropy oxide is formed. This special structure makes it have good cycle stability.

[0021] The present invention also discloses the application of the above nano core-shell structured high-entropy oxide in the preparation of the anode material for lithium-ion batteries. When the nano core-shell structured high-entropy oxide is used as the anode material for lithium-ion batteries, it shows extremely high lithium storage specific capacity and excellent cycle stability. At a current density of 0.1 A / g, the initial discharge specific capacity is as high as 1488.3 mAh / g. After 50 cycles, its capacity still remains at about 1174.15 mAh / g. Description of the Drawings

[0022] Figure 1 XRD pattern of the nano core-shell structured high-entropy oxide prepared in Example 1 of the present invention;

[0023] Figure 2 SEM image of the nano core-shell structured high-entropy oxide prepared in Example 1 of the present invention;

[0024] Figure 3 Battery cycle performance graph of the nano core-shell structured high-entropy oxide prepared in Example 1 of the present invention as the battery anode. Detailed Embodiments

[0025] To enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention.

[0026] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances so that the embodiments of the present invention described here can be implemented in an order different from those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0027] The present invention will be further described in detail below in conjunction with the accompanying drawings:

[0028] A low-temperature preparation method of a nano core-shell structured high-entropy oxide, comprising the following steps:

[0029] First, weigh 5 - 10 mL of glycerol and dissolve it in 55 - 65 mL of isopropanol to obtain a mixed solution A. Then, weigh 0.1 - 0.15 mmol of iron source, 0.1 - 0.15 mmol of cobalt source, 0.1 - 0.15 mmol of nickel source, 0.1 - 0.15 mmol of chromium source, and 0.1 - 0.15 mmol of manganese source respectively, add them to the mixed solution A, and place it on a magnetic stirrer to stir at room temperature for 1 - 3 h until completely dissolved to obtain a mixed solution B. Subsequently, put the mixed solution B into a high-pressure reactor with a volume of 100 mL, tighten it, and then heat and pressurize it in an oven. Set the reaction temperature to 150 - 200 °C and react for 8 - 24 h to observe the morphological changes and growth rules of the product. After the temperature in the oven drops to room temperature, centrifuge and wash the product with ethanol repeatedly for 2 - 5 times, then put the sample into a drying oven to dry. After the sample is dried, the HEO precursor can be obtained. Finally, put the synthesized HEO precursor into an air furnace and react for 2 - 4 h under the conditions of a reaction temperature of 400 - 600 °C and a heating rate of 2 - 10 °C / min. After the reaction is completed and cooled to room temperature, the collected sample is the high-entropy oxide with a nano core-shell structure. The high-entropy oxide with a nano core-shell structure has a typical spherical morphology. As the annealing temperature gradually increases, the inside of the nanosphere begins to shrink, forming a gap between the inner core and the outer shell, and finally forming the high-entropy oxide with a nano core-shell structure. This special structure endows it with good cycle stability.

[0030] Among them, the iron source is Fe(NO3)3, Fe2(SO4)3, FeCl3 or Fe(OH)(CH3COO)2; the cobalt source is Co(NO3)2, CoSO4, CoCl2 or (CH3COO)2Co; the nickel source is NiCl2, NiSO4, Ni(NO3)2 or Ni(CH3COO)2; the chromium source is Cr(NO3)3, Cr2(SO4)3, CrCl3, or (CH3COO)3Cr; the manganese source is Mn(NO3)2, MnSO4, MnCl2 or (CH3COO)2Mn.

[0031] Example 1

[0032] Dissolve Fe(NO3)3, Co(NO3)2, NiCl2, Mn(NO3)2 and Cr(NO3)3 with a molar ratio of 0.12 mmol: 0.12 mmol: 0.12 mmol: 0.12 mmol: 0.12 mmol in terms of molar parts into a mixed solution A composed of 60 mL of isopropanol and 8 mL of glycerol. After stirring for 1.5 h until completely dissolved, place it into a 100 mL high-pressure reactor, tighten it, then put it into an oven and raise the temperature and pressure. Set the reaction temperature to 180 °C and react for 12 h. After the oven temperature cools to room temperature, centrifuge and wash the product generated by the reaction with ethanol repeatedly for 4 times, and then put it into the oven to dry until the sample is dry, thus obtaining the HEO precursor. Finally, put the obtained HEO precursor into a muffle furnace and calcine it at a temperature of 550 °C and a rate of 5 °C / min for 2 h. After calcination, wait for the temperature in the furnace to cool to room temperature to obtain the high-entropy oxide with a nano core-shell structure.

[0033] See Figure 1 XRD pattern of the high-entropy oxide with a nano core-shell structure prepared in Example 1 of the present invention; from Figure 1 It can be seen that the synthesized product shows five diffraction peaks at 18.3°, 30.2°, 35.5°, 43.2°, 57.1° and 62.8°, corresponding to the (111), (220), (311), (400), (511) and (440) planes (PDF#54-0964) of the high-entropy oxide respectively. Therefore, it is judged that the high-entropy oxide is successfully synthesized and has a high purity.

[0034] See Figure 2 SEM image of the high-entropy oxide with a nano core-shell structure prepared in Example 1 of the present invention; from Figure 2 It can be seen that the high-entropy oxide with a nano core-shell structure has a typical spherical morphology, and the size is uniform, with a particle size of 500 - 700 nm. As the annealing temperature gradually increases, the inside of the nano-spheres begins to shrink, forming a void between the inner core and the outer shell, and finally forming the high-entropy oxide with a nano core-shell structure. This special structure endows it with good cycle stability.

[0035] See Figure 3 Battery cycle performance graph of the high-entropy oxide with a nano core-shell structure prepared in Example 1 of the present invention as the battery anode; from Figure 3 It can be seen that at a current density of 0.1 A / g, the anode of the high-entropy oxide with a nano core-shell structure shows excellent cycle performance, and its capacity still remains at about 1174.15 mAh / g after 50 cycles.

[0036] Example 2

[0037] By mole fraction, Fe(NO3)3, Co(NO3)2, NiCl2, Mn(NO3)2 and Cr(NO3)3 with a molar ratio of 0.1 mmol: 0.1 mmol: 0.1 mmol: 0.1 mmol: 0.1 mmol were dissolved in a mixed solution A composed of 55 mL of isopropanol and 5 mL of glycerol. After stirring for 1 h until completely dissolved, it was placed in a 100 mL autoclave. After tightening, it was placed in an oven and heated and pressurized. The reaction temperature was set at 150 °C and the reaction was carried out for 8 h. After the oven temperature cooled to room temperature, the product formed by the reaction was centrifuged and washed repeatedly with ethanol 2 times, and then placed in an oven to dry until the sample was dry, and the HEO precursor could be obtained. Finally, the obtained HEO precursor was placed in a muffle furnace and calcined at a temperature of 400 °C and a rate of 2 °C / min for 2 h. After calcination, when the furnace temperature cooled to room temperature, a nano core-shell structured high-entropy oxide was obtained.

[0038] Example 3

[0039] By mole fraction, Fe2(SO4)3, CoSO4, NiSO4, MnSO4 and Cr2(SO4)3 with a molar ratio of 0.1 mmol: 0.1 mmol: 0.1 mmol: 0.1 mmol: 0.1 mmol were dissolved in a mixed solution A composed of 60 mL of isopropanol and 8 mL of glycerol. After stirring for 2 h until completely dissolved, it was placed in a 100 mL autoclave. After tightening, it was placed in an oven and heated and pressurized. The reaction temperature was set at 180 °C and the reaction was carried out for 12 h. After the oven temperature cooled to room temperature, the product formed by the reaction was centrifuged and washed repeatedly with ethanol 4 times, and then placed in an oven to dry until the sample was dry, and the HEO precursor could be obtained. Finally, the obtained HEO precursor was placed in a muffle furnace and calcined at a temperature of 550 °C and a rate of 5 °C / min for 2 h. After calcination, when the furnace temperature cooled to room temperature, a nano core-shell structured high-entropy oxide was obtained.

[0040] Example 4

[0041] By molar fraction, FeCl3, CoCl2, Ni(NO3)2, MnCl2 and CrCl3 with a molar ratio of 0.15 mmol: 0.15 mmol: 0.15 mmol: 0.15 mmol: 0.15 mmol were dissolved in a mixed solution A composed of 60 mL of isopropanol and 8 mL of glycerol. After stirring for 2 h until completely dissolved, it was placed in a 100 mL autoclave. After tightening, it was placed in an oven and heated and pressurized. The reaction temperature was set at 180 °C and the reaction was carried out for 12 h. After the oven temperature cooled to room temperature, the product formed by the reaction was centrifuged and washed repeatedly with ethanol 4 times, and then placed in an oven to dry until the sample was dry, and the HEO precursor could be obtained. Finally, the obtained HEO precursor was placed in a muffle furnace and calcined at a temperature of 550 °C and a rate of 5 °C / min for 2 h. After calcination, when the furnace temperature cooled to room temperature, a nano core-shell structured high entropy oxide was obtained.

[0042] Example 5

[0043] By molar mass fraction, Fe(OH)(CH3COO)2, (CH3COO)2Co, Ni(CH3COO)2, (CH3COO)2Mn and (CH3COO)3Cr with a molar ratio of 0.15 mmol: 0.15 mmol: 0.15 mmol: 0.15 mmol: 0.15 mmol were dissolved in a mixed solution A composed of 65 mL of isopropanol and 10 mL of glycerol. After stirring for 3 h until completely dissolved, it was placed in a 100 mL autoclave. After tightening, it was placed in an oven and heated and pressurized. The reaction temperature was set at 200 °C and the reaction was carried out for 24 h. After the oven temperature cooled to room temperature, the product formed by the reaction was centrifuged and washed repeatedly with ethanol 5 times, and then placed in an oven to dry until the sample was dry, and the HEO precursor could be obtained. Finally, the obtained HEO precursor was placed in a muffle furnace and calcined at a temperature of 600 °C and a rate of 10 °C / min for 4 h. After calcination, when the furnace temperature cooled to room temperature, a nano core-shell structured high entropy oxide was obtained.

[0044] The above content is only to illustrate the technical idea of the present invention, and the protection scope of the present invention cannot be limited thereby. Any changes made on the basis of the technical solution according to the technical idea proposed by the present invention fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a nano core-shell structured high-entropy oxide at low temperature, characterized in that, It includes: First, add iron source, cobalt source, nickel source, chromium source and manganese source into the mixed solution composed of glycerol and isopropanol, and stir evenly; Then, through solvothermal reaction, washing and drying, and calcination, a nano core-shell structured high-entropy oxide is obtained.

2. The low-temperature preparation method of the nano core-shell structured high-entropy oxide according to claim 1, characterized in that, The dosage ratio of the iron source: cobalt source: nickel source: chromium source: manganese source: glycerol: isopropanol is (0.1 - 0.15) mmol: (0.1 - 0.15) mmol: (0.1 - 0.15) mmol: (0.1 - 0.15) mmol: (0.1 - 0.15) mmol: (5 - 10) mL: (55 - 65) mL.

3. The low-temperature preparation method of the nano core-shell structured high-entropy oxide according to claim 1, characterized in that, The temperature of the solvothermal reaction is 150 - 200 °C; the time of the solvothermal reaction is 8 - 24 h.

4. The low-temperature preparation method of the nano core-shell structured high-entropy oxide according to claim 1, characterized in that, The temperature of the calcination is 400 - 600 °C; the time of the calcination is 2 - 4 h.

5. The low-temperature preparation method of the nano core-shell structured high-entropy oxide according to claim 1, characterized in that, The heating rate of the calcination is 2 - 10 °C / min.

6. The low-temperature preparation method of the nano core-shell structured high-entropy oxide according to claim 1, characterized in that, The iron source is Fe(NO3)3, Fe2(SO4)3, FeCl3 or Fe(OH)(CH3COO)2; the cobalt source is Co(NO3)2, CoSO4, CoCl2 or (CH3COO)2Co; the nickel source is NiCl2, NiSO4, Ni(NO3)2 or Ni(CH3COO)2; the chromium source is Cr(NO3)3, Cr2(SO4)3, CrCl3 or (CH3COO)3Cr; the manganese source is Mn(NO3)2, MnSO4, MnCl2 or (CH3COO)2Mn.

7. The low-temperature preparation method of the nano core-shell structured high-entropy oxide according to claim 1, wherein, The stirring time is 1 - 3 h.

8. The low-temperature preparation method of the nano core-shell structured high-entropy oxide according to claim 1, characterized in that, The washing condition is to wash 2 - 5 times with absolute ethanol during centrifugation.

9. The nano core-shell structured high-entropy oxide prepared by the preparation method according to any one of claims 1 - 8.

10. The application of the nano core-shell structured high-entropy oxide according to claim 9 in the preparation of the anode material for lithium-ion batteries.

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