A Li2Fe for lithium-ion batteries x Mg y Al z Preparation method of O2@C composite material

Abstract

The application belongs to the field of lithium ion battery raw materials, and particularly relates to a preparation method of a Li2FexMgyAlzO2@C composite material for a lithium ion battery. x Mg y Al z O2@C composite material for a lithium ion battery. Through the method, the obtained Li2Fe x Mg y Al z O2@C composite material is stable in structure, uniform in particle size, good in conductivity, and simple in preparation process, and raw materials are cheap and easy to obtain, production cost is low, and the method is easy to popularize in industrial production.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery raw materials, specifically relating to a Li2Fe alloy for lithium-ion batteries. x Mg y Al z Preparation method of O2@C composite material. Background Technology

[0002] With the rapid development of consumer electronics and electric vehicles, higher demands are being placed on the energy density of lithium-ion batteries to achieve longer standby times and driving ranges. Currently, commercial lithium-ion batteries typically use silicon-based anode materials to improve energy density. However, during charging and discharging, due to the formation of the SEI film, the initial irreversible capacity of silicon-based anodes exceeds 20%, severely reducing the battery's energy density. Therefore, researchers are using lithium replenishment technology to compensate for lithium loss during the initial charging process and improve the energy density of lithium-ion batteries.

[0003] Lithium replenishment technology is divided into negative electrode lithium replenishment and positive electrode lithium replenishment. Negative electrode lithium replenishment materials are mostly metallic lithium materials, which are extremely unstable in air. Furthermore, the lithium replenishment technology is complex and has stringent environmental requirements, making widespread application difficult in the short term. Positive electrode lithium replenishment materials are mostly lithium-rich compounds, which are relatively stable. The lithium replenishment technology is simple, requires minimal changes to existing battery manufacturing processes, and is easier to implement.

[0004] Li₂NiO₂, as an important lithium-rich compound material, has been extensively studied. However, Ni is expensive and has a high oxidation voltage, requiring high voltage to release Li, which places high demands on the battery system. Li₂FeO₂ has the same structure as Li₂NiO₂ and is also a lithium-rich compound material. Lithium ions are released when charged to 4.3V, with an initial charge capacity exceeding 400mAh / g. As a cathode lithium replenishment material, it can significantly improve the energy density of lithium-ion batteries. However, Li₂FeO₂ has a high residual lithium content on its surface and poor surface stability; and Fe... 2+ Li₂FeO₂ is unstable and easily oxidized in humid air, resulting in structural instability. Therefore, coating and doping modification of Li₂FeO₂ materials are important ways to improve their structural stability.

[0005] Patent CN 112174216A discloses a cathode material, its preparation method, and a lithium-ion battery. The preparation method includes: (1) mixing and crushing the reaction raw materials to obtain a mixed powder; (2) heating and reacting the mixed powder obtained in step (1) under a protective atmosphere to obtain the cathode material. This method synthesizes a Li2FeO2 cathode material, but does not optimize the structure of the Li2FeO2 material, resulting in a low initial charge capacity.

[0006] This invention introduces Mg and Al into Li2FeO2 materials to improve their structural stability; the presence of a carbon coating layer can refine the Li2FeO2 structure. x Mg y Al z O2 material particle size, to avoid refining Li2Fe x Mg y Al z O2 material comes into direct contact with the electrolyte, causing Fe 4+ Oxidative decomposition of the electrolyte, while simultaneously increasing Li2Fe x Mg y Al z Electrical conductivity of O2 materials. Summary of the Invention

[0007] The purpose of this invention is to solve the problem of poor structural stability of Li2FeO2 materials and to provide a Li2FeO2 material suitable for lithium-ion batteries. x Mg y Al z The preparation method of O2@C composite material not only improves the structural stability of Li2FeO2 material, but also improves the electrical conductivity and battery adaptability of the material.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] In a first aspect, the present invention provides a lithium-ion battery Li2Fe x Mg y Al z In the O2@C composite material, x, y, z satisfy: 0 ≤ x, y, z ≤ 1, and x + y + 1.5z = 1; carbon material is coated on Li2Fe. x Mg y Al z O2 material surface.

[0010] Preferably, the Li2Fe x Mg y Al z The particle size of the O2@C composite material is 0.05–2 μm.

[0011] Preferably, the Li2Fe x Mg y Al z O2@C composite material, the carbon content of the composite material is 1-20wt%.

[0012] Secondly, the present invention provides a Li2Fe for lithium-ion batteries. x Mg y Al zThe preparation method of O2@C composite material, the specific steps are as follows:

[0013] Preparation of S1 mixed solution:

[0014] Ferric acetate, magnesium acetate, aluminum acetate, lithium acetate, and citric acid are dissolved in deionized water to form a mixed solution; the amount of citric acid is greater than or equal to the sum of the amounts of ferric acetate, magnesium acetate, aluminum acetate, and lithium acetate; the amount of lithium acetate is (2.0–2.5) × (the sum of the amounts of ferric acetate, magnesium acetate, and aluminum acetate).

[0015] Preparation of S2 precursor:

[0016] The mixed solution obtained in step S1 is heated at 60–90°C to obtain a wet gel. The wet gel is then heated at 10°C. -3 Dry gel is obtained by drying under a vacuum of ~1000Pa at 100~150℃. The resulting dry gel is the precursor.

[0017] S3Li2Fe x Mg y Al z Preparation of O2@C composite material:

[0018] The precursor obtained in step S2 is heat-treated at 400–1000 °C under a protective atmosphere until the reaction is complete, to obtain Li2Fe for lithium-ion batteries. x Mg y Al z O2@C composite material;

[0019] The protective atmosphere is any one or a combination of two or more of nitrogen, argon, acetylene, ethylene, methane, or ethane.

[0020] Preferably, in step S1, the drying time is 1 to 24 hours.

[0021] Preferably, in step S3, the heat treatment time is 1 to 24 hours.

[0022] Thirdly, the present invention provides a Li2Fe as described in the first aspect. x Mg y Al z Applications of O2@C composite materials in the preparation of lithium-ion batteries.

[0023] Preferably, the Li2Fe x Mg y Al z O2@C composite material is used to prepare the positive electrode of lithium-ion batteries.

[0024] The beneficial effects of this invention: This method prepares Li2Fe for lithium-ion batteries. x Mgy Al z O2@C composite materials have the following advantages:

[0025] (1) Prepared Li2Fe x Mg y Al z The O2@C composite material has a particle size of 0.05–2 μm, has a higher specific surface area, and makes it easier for lithium ions to be extracted.

[0026] (2) Introducing Mg and Al into Li2FeO2 material significantly improves the structural stability of Li2FeO2 material;

[0027] (3) The carbon coating layer is uniformly coated on Li2Fe x Mg y Al z O2 particles can refine Li2Fe x Mg y Al z O2 material particle size, preventing Li2Fe x Mg y Al z O2 material comes into direct contact with the electrolyte, avoiding Fe 4+ Oxidation of the electrolyte, while simultaneously increasing Li2Fe x Mg y Al z Electrical conductivity of O2 materials;

[0028] (4) Preparation of Li2Fe for lithium-ion batteries x Mg y Al z O2@C composite materials have a simple process, low production cost, and are easy to industrialize and promote. Attached Figure Description

[0029] Figure 1 Prepared Li2Fe x Mg y Al z SEM image of O2@C composite material;

[0030] Figure 2 Prepared Li2Fe x Mg y Al z TEM image of O2@C composite material. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and examples.

[0032] Example 1

[0033] Li2Fe for lithium-ion batteries x Mg y Al z The preparation steps of O2@C composite material are as follows:

[0034] Step 1, Preparation of Mixed Solution

[0035] Dissolve 0.015 mol ferric acetate, 0.002 mol magnesium acetate, 0.002 mol aluminum acetate, 0.044 mol lithium acetate and 0.09 mol citric acid in deionized water to form a mixed solution;

[0036] Step 2, Precursor Preparation

[0037] The mixed solution obtained in step one is heated at 70°C to obtain a wet gel. The wet gel is dried at 110°C under a vacuum of 100Pa for 10 hours to obtain a dry gel, which is the precursor.

[0038] Step 3, Li2Fe x Mg y Al z Preparation of O2@C composite materials

[0039] The precursor obtained in step two was placed in a sintering furnace and heat-treated at 750°C for 10 hours under an argon protective atmosphere to obtain Li2Fe for lithium-ion batteries. 0.75 Mg 0.1 Al 0.1 O2@C composite material;

[0040] Prepared Li2Fe 0.75 Mg 0.1 Al 0.1 SEM image of O2@C composite material as shown below Figure 1 As shown, the particle size of the composite material is ≤100nm;

[0041] For Li2Fe 0.75 Mg 0.1 Al 0.1 Elemental analysis of the O2@C composite material revealed a carbon content of 16.3 wt%.

[0042] Example 2

[0043] Li2Fe for lithium-ion batteries x Mg y Al z The preparation steps of O2@C composite material are as follows:

[0044] Step 1, Preparation of Mixed Solution

[0045] Dissolve 0.015 mol ferric acetate, 0.002 mol magnesium acetate, 0.002 mol aluminum acetate, 0.04 mol lithium acetate and 0.06 mol citric acid in deionized water to form a mixed solution;

[0046] Step 2, Precursor Preparation

[0047] The mixed solution obtained in step one was heated to 90°C to obtain a wet gel. The wet gel was then subjected to 10... -1 Under a vacuum of Pa, the product was dried at 130°C for 3 hours to obtain a dry gel, which is the precursor.

[0048] Step 3, Li2Fe x Mg y Al z Preparation of O2@C composite materials

[0049] The precursor obtained in step two was placed in a sintering furnace and heat-treated at 850°C for 5 hours under a protective atmosphere of nitrogen and acetylene mixture to obtain Li2Fe for lithium-ion batteries. 0.75 Mg 0.1 Al 0.1 O2@C composite material;

[0050] Prepared Li2Fe 0.75 Mg 0.1 Al 0.1 O2@C composite material with a particle size of approximately 200 nm;

[0051] Prepared Li2Fe 0.75 Mg 0.1 Al 0.1 TEM image of O2@C composite material as shown below Figure 2 As shown, carbon material is uniformly coated on Li2Fe. 0.75 Mg 0.1 Al 0.1 The surface of the O2 material was coated with a thickness of 20-40 nm. Elemental analysis of the composite material showed that the carbon content in the composite material was 10.8 wt%.

[0052] Prepared Li2Fe 0.75 Mg 0.1 Al 0.1 O2@C composite material and lithium metal were packaged into button cells. Constant current charge-discharge tests were conducted at a current density of 0.05C within a voltage range of 1.5–4.6V. (Li2Fe) 0.75 Mg 0.1 Al 0.1 The O2@C composite material achieved an initial charge capacity of 326mAh / g, demonstrating excellent lithium release capability.

Claims

1. A lithium-ion battery Li2Fe x Mg y Al z O2@C composite material, characterized in that, The Li2Fe x Mg y Al z In the O2@C composite material, x, y, z satisfy: 0 < x, y, z < 1, and x + y + 1.5z = 1; carbon material is coated on Li2Fe. x Mg y Al z O2 material surface; The Li2Fe x Mg y Al z O2@C composite material, characterized in that the Li2Fe x Mg y Al z The particle size of the O2@C composite material is 0.05~2 μm; the carbon content in the composite material is 1~20 wt%.

2. The lithium-ion battery Li2Fe as described in claim 1 x Mg y Al z The method for preparing O2@C composite material is characterized by, The specific steps are as follows: Preparation of S1 mixed solution: Ferric acetate, magnesium acetate, aluminum acetate, lithium acetate, and citric acid are dissolved in deionized water to form a mixed solution; the amount of citric acid is greater than or equal to the sum of the amounts of ferric acetate, magnesium acetate, aluminum acetate, and lithium acetate; the amount of lithium acetate is (2.0~2.5) × (the sum of the amounts of ferric acetate, magnesium acetate, and aluminum acetate). Preparation of S2 precursor: The mixed solution obtained in step S1 is heated at 60-90°C to obtain a wet gel. The wet gel is then heated at 10°C. -3 Dry gel is obtained by drying at 100~150℃ for 1~24 h under a vacuum of ~1000 Pa. The resulting dry gel is the precursor. S3Li2Fe x Mg y Al z Preparation of O2@C composite materials: The precursor obtained in step S2 is heat-treated at 400-1000℃ for 1-24 h under a protective atmosphere to obtain Li2Fe for lithium-ion batteries. x Mg y Al z O2@C composite material; The protective atmosphere is any one or a combination of two or more of nitrogen, argon, acetylene, ethylene, methane, or ethane.

3. The lithium-ion battery Li2Fe as described in claim 1 x Mg y Al z Applications of O2@C composite materials in the preparation of lithium-ion batteries.

4. The lithium-ion battery Li2Fe according to claim 3 x Mg y Al z The application of O2@C composite material in the preparation of lithium-ion batteries is characterized by, The Li2Fe x Mg y Al z O2@C composite material is used to prepare the positive electrode of lithium-ion batteries.

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