A high entropy metal oxide material for lithium-ion battery negative electrode and its preparation method and application

Abstract

The present invention discloses a high entropy metal oxide material for lithium ion battery negative electrode and its preparation method and application. The chemical formula of the high entropy metal oxide material provided by the present invention is (Fe 1 / 6Co 1 / 6 Mg 1 / 6 Cr 1 / 6 Li 1 / 6 Zn 1 / 6 )3O4, prepared by solution combustion method using nitrates of six metals and organic fuel as raw materials. The high entropy metal oxide material of the present invention has good rate performance and cycle stability when used for the negative electrode of lithium-ion batteries. After 150 cycles at a current density of 100mA / g, the reversible specific capacity can reach more than 650mAh / g. At the same time, after 2000 cycles at a high current density of 2000mA / g, the capacity remains above 100mAh / g, showing excellent cycle stability; when the current drops from the high current density of 2000mA / g to 100mA / g, the capacity is almost completely restored, and the recovery rate reaches more than 99.5%, showing excellent rate performance. At the same time, the process is simple, the production efficiency is high, the energy consumption is low, the repeatability is good, and it has good practical application value.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery materials, and in particular to a high-entropy metal oxide material for a lithium-ion battery negative electrode, a preparation method thereof, and an application thereof. Background Art

[0002] The information disclosed in the background of the invention is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to a person skilled in the art.

[0003] Currently, graphitized carbon materials are the main negative electrode materials for commercial lithium-ion batteries, but their theoretical specific capacity is quite low (372 mAh g -1 ), which limits the application scenarios of graphite carbon materials. Transition metal oxides have higher theoretical specific capacity than graphite, and therefore have attracted widespread attention from researchers in recent years. However, they are prone to component segregation and volume changes during the reaction process, resulting in severe attenuation of specific capacity and thus damaging the battery.

[0004] The emergence of high-entropy materials has greatly improved this problem. The gradual increase in entropy reduces the Gibbs free energy, allowing the formation of a stable mixture system. This type of material is also known as a high-entropy material. High-entropy materials have four core effects: high entropy effect, hysteresis diffusion effect, lattice distortion effect, and cocktail effect. These four effects give high-entropy materials better physical and chemical properties than single-component materials.

[0005] At present, most of the high entropy oxide negative electrodes for lithium-ion batteries reported in the prior art are five-component transition metal elements with equal molar ratios, showing a rock salt structure, such as (MgCoNiCuZn)O. In addition, most of the metals involved are divalent. The excellence of high entropy transition metal oxides (HEOs) is that by changing the constituent elements, concentrations and crystal structures of HEOs, infinite possibilities with various and even novel functional properties can be achieved. This extends to high entropy oxides with other structures, such as high entropy spinel oxides. Compared with rock salt structure high entropy oxides, spinel-type high entropy oxides have two Wyckoff sites and a large number of oxygen vacancies, which are conducive to reversible lithiation and delithiation. For example, the recently reported spinel (Mg 0.2 Ti 0.2 Zn 0.2 Cu 0.2 Fe 0.2)3O4 negative electrode material (RSCA Advances, 2020, 10(16):9736-44). After testing, it was found that after 300 long-term charge and discharge cycles at 100mA / g, the capacity can still reach 504mAh / g. However, due to the designability of high-entropy components, its reversible capacity and cycle stability have much room for improvement.

[0006] At the same time, relevant studies have shown that the incorporation of lithium helps to improve the specific capacity of negative electrode materials. However, the ionic radius of lithium is very different from that of other transition metal oxide ions. The incorporation of lithium will affect the spinel structure of the high-entropy material to a certain extent, thereby affecting its stability. Patent CN 112537804 B (authorization announcement date: 2023.01.31) discloses a series of lithium-doped high-entropy oxide battery negative electrode materials. From its disclosed electrochemical properties, it can be seen that high-entropy oxide battery negative electrode materials with different elemental compositions exhibit different electrochemical properties. How to further improve the reversible capacity of high-entropy metal oxide negative electrode materials, especially the cycle stability, has become an urgent problem to be solved. Summary of the Invention

[0007] In view of this, the present invention provides a high-entropy metal oxide material for lithium-ion battery negative electrode and its preparation method and application, which solves the problems of poor cycle performance and poor rate performance of high-entropy metal oxide negative electrode materials.

[0008] In the first aspect, the present invention provides a high entropy metal oxide material for the negative electrode of a lithium ion battery, the chemical formula of which is (Fe 1 / 6 Co 1 / 6 Mg 1 / 6 Cr 1 / 6 Li 1 / 6 Zn 1 / 6 )3O4.

[0009] In a second aspect, the present invention provides a method for preparing the above-mentioned high entropy metal oxide material, comprising the following steps:

[0010] Weighing nitrates of Fe, Co, Mg, Cr, Li, and Zn, dissolving them in water, and stirring to obtain a mixed solution; wherein the molar ratio of Fe, Co, Mg, Cr, Li, and Zn is 0.95-1.05:0.95-1.05:0.95-1.05:0.95-1.05:0.95-1.05:0.95-1.05;

[0011] adding an organic fuel to the mixed solution and stirring the mixture at room temperature to obtain a sol;

[0012] The sol is dried to obtain a gel, and the gel is sequentially calcined, ground, and sieved to obtain the product.

[0013] Preferably, the molar ratio of Fe, Co, Mg, Cr, Li and Zn is 1:1:1:1:1:1.

[0014] Preferably, in the mixed solution, the total concentration of nitrates of Fe, Co, Mg, Cr, Li and Zn is 2 to 6 mol / L.

[0015] Preferably, the organic fuel is selected from one or more of citric acid, glycine, urea and glucose.

[0016] Preferably, the drying temperature is 100-120° C., and the drying time is 10-20 hours.

[0017] Preferably, the calcination temperature is 750-850° C., the calcination time is 30-40 min, and the heating rate during the calcination process is 5-10° C. / min.

[0018] In a third aspect, the present invention provides the use of the above-mentioned high-entropy metal oxide material or the high-entropy metal oxide material prepared by the above-mentioned preparation method in the negative electrode material of a lithium-ion battery.

[0019] In a fourth aspect, the present invention provides a lithium-ion battery negative electrode, comprising a current collector, a conductive agent, a binder and a negative electrode active material layer; the negative electrode active material layer comprises the above-mentioned high entropy metal oxide material.

[0020] In a fifth aspect, the present invention provides a lithium-ion battery comprising the above-mentioned lithium-ion battery negative electrode, a lithium-ion battery positive electrode, and a separator disposed between the lithium-ion battery positive electrode and the lithium-ion battery negative electrode.

[0021] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0022] (1) The present invention customizes a high entropy metal oxide with a spinel structure by screening specific elements, and provides a chemical formula (Fe 1 / 6 Co 1 / 6 Mg 1 / 6 Cr 1 / 6 Li 1 / 6 Zn 1 / 6)3O4 high-entropy metal oxide material, when used for the negative electrode of lithium-ion batteries, has high specific capacity, good rate performance and cycle stability. After 150 cycles at a current density of 100mA / g, the reversible specific capacity can reach more than 650mAh / g. At the same time, after 2000 cycles at a high current density of 2000mA / g, the capacity remains above 100mAh / g, showing excellent cycle stability and a coulombic efficiency close to 100%. When the current drops from the high current density of 2000mA / g back to 100mA / g, the capacity is almost completely recovered, with a recovery rate of more than 99.5%, showing excellent rate performance, which can meet the use requirements in specific scenarios;

[0023] (2) The technical solution provided by the present invention has a simple process and high production efficiency. It not only solves the problem of mass production, but also has low energy consumption and good repeatability, and therefore has good practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The drawings, which constitute part of the present invention, are intended to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are intended to explain the present invention and do not constitute undue limitations thereon. It is obvious that one of ordinary skill in the art could derive other drawings based on these drawings without inventive effort.

[0025] Figure 1 This is the X-ray diffraction pattern of the spinel high-entropy metal oxide nanomaterial prepared in Example 1 of the present invention;

[0026] Figure 2 This is a scanning electron microscope photograph of the spinel high-entropy metal oxide nanomaterial prepared in Example 1 of the present invention;

[0027] Figure 3 This is the X-ray diffraction pattern of the spinel high-entropy metal oxide nanomaterial prepared in Example 2 of the present invention;

[0028] Figure 4 This is a scanning electron microscope photograph of the spinel high-entropy metal oxide nanomaterial prepared in Example 2 of the present invention;

[0029] Figure 5 This is the X-ray diffraction pattern of the spinel high-entropy metal oxide nanomaterial prepared in Example 3 of the present invention;

[0030] Figure 6 This is a scanning electron microscope photograph of the spinel high-entropy metal oxide nanomaterial prepared in Example 3 of the present invention;

[0031] Figure 7This is a graph showing the electrochemical rate performance of the spinel high-entropy metal oxide nanomaterial electrode prepared in Example 2 of the present invention;

[0032] Figure 8 This is a cycling stability test of the spinel high entropy metal oxide nanomaterial electrode prepared in Example 2 of the present invention at a current density of 100 mA / g;

[0033] Figure 9 The spinel high entropy metal oxide nanomaterial electrode prepared in Example 2 of the present invention has a cycle performance of 2000 times at 2000 mA / g. DETAILED DESCRIPTION

[0034] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present invention belongs.

[0035] The present invention provides a high entropy metal oxide material for the negative electrode of a lithium ion battery, the chemical formula of which is (Fe 1 / 6 Co 1 / 6 Mg 1 / 6 Cr 1 / 6 Li 1 / 6 Zn 1 / 6 )3O4.

[0036] In the present invention, iron (Fe) as one of the main metal elements helps to improve the electrical conductivity and stability of the material in the spinel structure, and also affects the structure and electrochemical properties of the material. The addition of cobalt (Co) helps to improve the electronic conductivity of the material, and the cobalt element can also affect the lattice structure of the material, thereby affecting the performance and cycle life of the battery. The magnesium (Mg) element can increase the ion conductivity of the material, which helps to improve the electrochemical performance and cycle life of the lithium-ion battery. The addition of chromium (Cr) element can improve the structural stability and cycle resistance of the material, which helps to improve the cycle life and safety of the battery. Lithium (Li) element is the main active substance of lithium-ion batteries, participates in the insertion and deinsertion process of lithium ions, and affects the electrochemical performance and energy storage characteristics of the material. Zinc (Zn) element participates in the formation of the spinel structure and plays an important role in the crystal structure and stability of the material. Taken together, Fe, Co, Mg, and Cr are electrochemically active elements, Mg is an inactive element that stabilizes the lattice, and the addition of Li will introduce a large number of oxygen vacancies. The combined effects of these metal elements influence the electrochemical performance, cycle life, and safety of spinel oxides as negative electrode materials for lithium-ion batteries. Together, they form a complex lattice structure that significantly influences the material's performance.

[0037] The present invention also provides a method for preparing the high entropy metal oxide material, comprising the following steps:

[0038] Weighing nitrates of Fe, Co, Mg, Cr, Li, and Zn, dissolving them in water, and stirring to obtain a mixed solution; wherein the molar ratio of Fe, Co, Mg, Cr, Li, and Zn is 0.95-1.05:0.95-1.05:0.95-1.05:0.95-1.05:0.95-1.05:0.95-1.05;

[0039] adding an organic fuel to the mixed solution and stirring the mixture at room temperature to obtain a sol;

[0040] The sol is dried to obtain a gel, and the gel is sequentially calcined, ground, and sieved to obtain the product.

[0041] The present invention uses six specific metal nitrates and an organic fuel as the primary reactants. In this intense redox reaction, the nitrates are reduced by the organic matter, and the resulting system ignites at a specific temperature. Once ignited, a chemical reaction begins within the system using energy continuously supplied from outside the system. The combustion wave then propels the mixture into products during the reaction. This process can be completed in an extremely short time, resulting in an ultrafine powder. The present invention utilizes a solution combustion method to achieve the formation and solid solution diffusion of a single-phase high-entropy oxide. The resulting high-entropy metal oxide material exhibits the advantages of high purity, small particle size, and uniform elemental distribution, with a particle size of 50 to 200 nm.

[0042] In the present invention, the six metal nitrates are preferably mixed in equimolar amounts, that is, the molar ratio of Fe, Co, Mg, Cr, Li and Zn is 1:1:1:1:1:1.

[0043] In the mixed solution of the present invention, the total concentration of nitrates of Fe, Co, Mg, Cr, Li and Zn is 2 to 6 mol / L.

[0044] The organic fuel of the present invention is selected from one or more of citric acid, glycine, urea and glucose. The amount of the organic fuel added is determined by formula (1):

[0045]

[0046] In formula (1), M is the v-valent metal; parameter Indicates the ratio of organic fuel to oxidant (oxygen). Preferably 1 is selected.

[0047] In the present invention, the drying temperature is 100-120° C., and the drying time is 10-20 hours.

[0048] In the present invention, the calcination temperature is 750-850° C., the calcination time is 30-40 min, and the heating rate during the calcination process is 5-10° C. / min.

[0049] The present invention also provides the use of the high-entropy metal oxide material or the high-entropy metal oxide material prepared by the above preparation method in lithium-ion battery negative electrode materials.

[0050] The present invention also provides a lithium-ion battery negative electrode, comprising a current collector, a conductive agent, a binder and a negative electrode active material layer; the negative electrode active material layer comprises the above-mentioned high entropy metal oxide material, and the negative electrode active material layer and the conductive agent are formed on at least one surface of the current collector through the binder.

[0051] In the present invention, the binder is selected from one or more of polyvinylidene fluoride, polytetrafluoroethylene, sodium alginate, sodium carboxymethyl cellulose and SBR rubber; the current collector is selected from one or more of copper foil, aluminum foil, nickel foil, copper mesh, aluminum mesh and nickel mesh; the conductive agent is selected from one or more of acetylene black, natural graphite, artificial graphite, carbon fiber, carbon nanotubes, copper powder, copper mesh or metal.

[0052] In the present invention, the mass ratio of the negative electrode active material, the conductive agent and the binder is (60-80): (10-30): (10-30). The preparation method of the lithium ion battery negative electrode adopts the conventional preparation method of the lithium ion battery negative electrode in the field, which is not described here.

[0053] The present invention also provides a lithium-ion battery comprising the aforementioned lithium-ion battery negative electrode, a lithium-ion battery positive electrode, and a separator disposed between the lithium-ion battery positive electrode and the lithium-ion battery negative electrode. The lithium-ion battery positive electrode and separator of the present invention are not particularly limited, and any lithium-ion battery positive electrode and separator known to those skilled in the art may be used.

[0054] The technical solution of the present invention is further described below with reference to specific embodiments.

[0055] Example 1

[0056] This embodiment provides a spinel high entropy metal oxide nanomaterial. The specific preparation steps are as follows:

[0057] 1) weighing powder according to the molar ratio of Fe(NO3)3·9H2O:Co(NO3)2·6H2O:Mg(NO3)2·6H2O:Cr(NO3)3·9H2O:LiNO3:Zn(NO3)2·6H2O=1:0.95:1:1:1:1, and dissolving the powder in 10 ml of deionized water to obtain a mixed solution, wherein the total metal nitrate concentration of the mixed solution is controlled to be 3 mol / L;

[0058] 2) According to formula (1), glycine of corresponding mass was weighed and added to the above mixed solution, and stirred uniformly at room temperature to obtain a sol;

[0059]

[0060] 3) Place the mixed solution in an oven at 120°C for 12 hours to obtain a brown gel;

[0061] 4) Grind the gel into powder, place it in a muffle furnace, set the heating rate at 5°C / min, heat to 750°C and hold for 30 min;

[0062] 5) The calcined powder was ground in a mortar and then passed through a 300-mesh sieve to obtain a spinel high-entropy metal oxide nanomaterial.

[0063] The phase structure and micromorphology of the obtained spinel high entropy metal oxide nanomaterials are respectively Figure 1 and Figure 2 The X-ray diffraction pattern and scanning electron micrograph are shown. The XRD pattern shows that all peak positions of the powder are consistent with those of the standard PDF card PDF#97-007-7592, forming a single-phase spinel solid solution structure. The SEM image reveals a relatively uniform particle size distribution of 50-100 nm.

[0064] Example 2

[0065] This embodiment provides a spinel high entropy metal oxide nanomaterial. The specific preparation steps are as follows:

[0066] 1) Weighing powder according to the molar ratio of Fe(NO3)3·9H2O:Co(NO3)2·6H2O:Mg(NO3)2·6H2O:Cr(NO3)3·9H2O:LiNO3:Zn(NO3)2·6H2O=1:1:1:1:1:1, and dissolving the powder in 10 ml of deionized water to obtain a mixed solution, wherein the total metal nitrate concentration of the mixed solution is controlled to be 6 mol / L;

[0067] 2) According to formula (1), glycine of corresponding mass was weighed and added to the above mixed solution, and stirred uniformly at room temperature to obtain a sol;

[0068]

[0069] 3) Place the mixed solution in an oven at 120°C for 12 hours to obtain a brown gel;

[0070] 4) Grind the gel into powder, place it in a muffle furnace, set the heating rate at 5°C / min, heat to 800°C and keep it for 30 minutes;

[0071] 5) The calcined powder was ground in a mortar and then passed through a 300-mesh sieve to obtain a spinel high-entropy metal oxide nanomaterial.

[0072] The phase structure and micromorphology of the obtained spinel high entropy metal oxide nanomaterials are respectively Figure 3 and Figure 4 The X-ray diffraction pattern and scanning electron micrograph are shown. The XRD pattern shows that all peak positions of the powder are consistent with those of the standard PDF card PDF#97-019-5703, forming a single-phase spinel solid solution structure. The SEM image reveals a relatively uniform particle size distribution of 50-100 nm.

[0073] Example 3

[0074] This embodiment provides a spinel high entropy metal oxide nanomaterial. The specific preparation steps are as follows:

[0075] 1) Weighing powder according to the molar ratio of Fe(NO3)3·9H2O:Co(NO3)2·6H2O:Mg(NO3)2·6H2O:Cr(NO3)3·9H2O:LiNO3:Zn(NO3)2·6H2O=1:1.05:1:1:1:1, and dissolving the powder in 10 ml of deionized water to obtain a mixed solution, wherein the total metal nitrate concentration of the mixed solution is controlled to be 3 mol / L;

[0076] 2) According to formula (1), glycine of corresponding mass was weighed and added to the above mixed solution, and stirred uniformly at room temperature to obtain a sol;

[0077] 3) Place the mixed solution in an oven at 120°C for 12 hours to obtain a brown gel;

[0078] 4) Grind the gel into powder and place it in a muffle furnace. Set the heating rate to 5°C / min and heat to 850°C for 30 min.

[0079] 5) The calcined powder was ground in a mortar and then passed through a 300-mesh sieve to obtain a spinel high-entropy metal oxide nanomaterial.

[0080] The phase structure and micromorphology of the obtained spinel high entropy metal oxide nanomaterials are respectively Figure 5 and Figure 6The X-ray diffraction pattern and scanning electron microscopy (SEM) images are shown. The XRD pattern shows that all peak positions of the powder are consistent with those of the standard PDF card PDF#97-019-5704, forming a single-phase spinel solid solution structure. The SEM image reveals a relatively uniform particle size distribution of approximately 200 nm.

[0081] Test example

[0082] A 3% PVDF / NMP solution was pre-prepared: a certain amount of PVDF was weighed and dissolved in NMP, stirring thoroughly until the mixture was uniform. In a weighing bottle, the spinel high-entropy metal oxide nanomaterial prepared in Example 2 was uniformly mixed with PVDF and carbon black in a mass ratio of 8:1:1. After stirring for 12 hours on a magnetic stirrer at 400 rpm, a slurry was prepared. The slurry was evenly coated on a clean copper sheet, which was then dried in a vacuum drying oven at 100°C for 12 hours. After drying, the copper sheet was pressed into electrode sheets to assemble the battery. The mass of the active material was weighed and recorded, and the electrode sheets were then assembled into CR2032 button cells in a glove box. A lithium sheet was used as the counter electrode, and a solvent mixture with a volume ratio of EC:DMC = 1:1 vol% and 5.0% FEC was used. A lithium hexafluorophosphate (LiPF6) solution was used as the electrolyte. The battery was packaged using an automatic packaging machine, completing the battery preparation.

[0083] Galvanostatic Charge-Discharge (GCD) testing involves subjecting the prepared button cell to varying current densities, generating a voltage-versus-time curve. Continuous testing at a specific current verifies the material's cycling stability. Testing is performed on a CT3001A system within a voltage range of 0.01-3V.

[0084] like Figure 7 As shown, the high-entropy metal oxide nanomaterial electrode of Example 2 has good rate performance. At a current density of 2000 mA / g, the reversible capacity is 189.5 mAh / g, and its capacity retention rate is 40.3% compared to the value measured at 100 mA / g. When the current is reduced back to 100 mA / g, the capacity is almost fully recovered, with a recovery rate of 99.7%, demonstrating excellent rate performance.

[0085] Figure 8 The cycling stability test of the electrode at a current density of 100 mA / g shows that after 150 cycles, the reversible capacity reaches 650 mAh / g and continues to climb. This capacity increase can be attributed to the rearrangement of the negative electrode structure.

[0086] Figure 9The electrode is cycled for 2000 times at 2000 mA / g. After 2000 cycles, the capacity remains above 100 mAh / g, showing strong cycling stability and a Coulombic efficiency close to 100%.

[0087] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A high entropy metal oxide material for a lithium ion battery negative electrode, characterized in that: The chemical formula of the high entropy metal oxide material is (Fe 1 / 6 Co 1 / 6 Mg 1 / 6 Cr 1 / 6 Li 1 / 6 Zn 1 / 6 )3O4; The preparation method of the high entropy metal oxide material comprises the following steps: Weighing nitrates of Fe, Co, Mg, Cr, Li, and Zn, dissolving them in water, and stirring to obtain a mixed solution; wherein the molar ratio of Fe, Co, Mg, Cr, Li, and Zn is 0.95-1.05:0.95-1.05:0.95-1.05:0.95-1.05:0.95-1.05:0.95-1.05; adding an organic fuel to the mixed solution and stirring the mixture at room temperature to obtain a sol; The sol is dried to obtain a gel, and the gel is sequentially calcined, ground, and sieved to obtain the product.

2. The preparation method according to claim 1, wherein The molar ratio of Fe, Co, Mg, Cr, Li and Zn is 1:1:1:1:1:

1.

3. The preparation method according to claim 1, wherein In the mixed solution, the total concentration of nitrates of Fe, Co, Mg, Cr, Li and Zn is 2-6 mol / L.

4. The preparation method according to claim 1, wherein The organic fuel is selected from one or more of citric acid, glycine, urea and glucose.

5. The preparation method according to claim 1, wherein The drying temperature is 100-120° C., and the drying time is 10-20 hours.

6. The preparation method according to claim 1, wherein The calcination temperature is 750-850° C., the calcination time is 30-40 min, and the heating rate during the calcination process is 5-10° C. / min.

7. Use of the high entropy metal oxide material according to claim 1 or the high entropy metal oxide material prepared by the preparation method according to any one of claims 2 to 6 in a negative electrode material for a lithium ion battery.

8. A lithium ion battery negative electrode, characterized in that The invention comprises a current collector, a conductive agent, a binder and a negative electrode active material layer; the negative electrode active material layer comprises the high entropy metal oxide material according to claim 1.

9. A lithium-ion battery, characterized in that: The invention comprises the lithium ion battery negative electrode according to claim 8, a lithium ion battery positive electrode and a separator arranged between the lithium ion battery positive electrode and the lithium ion battery negative electrode.

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