Preparation method of lithium-rich lithium ferrite composite material and application of lithium-rich lithium ferrite composite material in lithium supplement

Abstract

The invention discloses a preparation method of a lithium-rich lithium ferrite composite material and application of the lithium-rich lithium ferrite composite material in lithium supplement. The lithium-rich lithium ferrite composite material comprises a lithium carbon compound, a carbon material and lithium-rich lithium ferrite particles, a three-phase interface of lithium-rich lithium ferrite, carbon and lithium carbon compound particles forms a multi-layer structure, the lithium-rich lithium ferrite composite material introduces a multifunctional group through compounding of carbon and lithium carbon compounds, increases an electronic structure of adjacent carbon atoms, and improves the performance of the lithium-rich lithium ferrite composite material. And the lithium ion battery has the characteristics of uniform structure and excellent electrochemical performance, and is excellent in lithium supplementing performance.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium-ion battery cathode lithium supplement materials, and more specifically, to a preparation method of a lithium-rich lithium ferrate composite material and its application in lithium supplement. Background Art

[0002] With the development of electronic technology, natural climate change, and the rapid consumption of fuel resources, the increase in electronic devices such as portable electronic devices (mobile phones, computers, and electric vehicles) has been driven. At the same time, there is also a trend of decreasing demand growth for fossil fuel consumption in society and a transformation of the new energy production / consumption structure from high-carbon to low-carbon and carbon-free. This requires an improvement in the performance of the power supply for electronic devices to meet the rapidly developing energy storage market for electronic devices. Therefore, it is an urgent task to develop a high-safe, high-energy-density, long-cycle-life, and low-cost energy storage battery to fill the large energy storage market. However, among the requirements of various energy storage applications, there are greater power densities, higher energy densities, and longer lifetimes compared to lead-acid batteries and nickel-cadmium batteries. Therefore, lithium-ion batteries have received wide attention in the energy storage market due to their advantages such as high energy density, long cycle life, and good safety.

[0003] Improving the energy density of lithium-ion batteries has attracted the attention of many researchers in the development of lithium-ion batteries. Among them, increasing the active lithium content in lithium-ion batteries to improve the energy density of lithium-ion batteries is a key focus direction and an important means to efficiently improve the energy density of lithium-ion batteries. When a lithium-ion battery is first charged after being encapsulated, lithium ions in the positive electrode migrate through the electrolyte and the separator to the negative electrode, and a thin film (solid electrolyte interface) is coated on the outer surface of the negative electrode material on the negative electrode side. The formation of the film will consume a large part of the lithium ions migrating from the positive electrode. However, the lithium ions in the solid electrolyte film formed during the first discharge process will not return to the positive electrode side, resulting in a large amount of lithium ions in the positive electrode being converted into Li 2 CO 3 and LiF, etc., are confined to the negative electrode, resulting in a large amount of irreversible lithium ions in the positive electrode material, so that the first charge-discharge efficiency and the energy density are reduced. At the same time, when a lithium-ion battery uses a negative electrode material with a larger volume change than graphite (such as: silicon negative electrode, silicon / carbon negative electrode, silicon oxide negative electrode), the large volume change of the negative electrode during the reaction will cause more lithium ions in the positive electrode to be consumed.

[0004] Therefore, in order to promote the improvement of the energy density of lithium-ion batteries, supplementing lithium ions in the lithium-ion battery system is a simple and efficient strategy. Among them, lithium supplementation on the negative electrode side cannot meet the existing production process of lithium-ion batteries, while lithium supplementation on the positive electrode side does not require changing the existing lithium-ion production process, so lithium supplementation on the positive electrode side has been widely studied. Among the positive electrode side lithium supplement materials, there is Li 2NiO 2 (CN113571781A), Li 2 O(CN112290022A) and Li 5 FeO 4 (CN112028126A), where Li 5 FeO 4 Among many cathode lithium supplement agents, it exhibits high specific capacity and high de-lithiation platform voltage (3.5 - 4.7V), and is a material for efficient lithium supplementation in the cathode. However, the lithium ions in its crystal structure are enriched and easily react with moisture and carbon dioxide in the air, resulting in the formation of by-products, affecting the lithium supplementation of the cathode material, and severely limiting its inherent properties. At the same time, it also increases the process difficulty of its mass production.

[0005] Therefore, it is necessary to solve the problem that the intrinsic lithium ions of lithium-rich lithium ferrate are prone to side reactions with titanium dioxide and moisture in the air, causing the material to deteriorate and resulting in unsatisfactory lithium supplementation effect on the cathode side. The usual treatment method is to perform surface modification and surface coating on Li 5 FeO 4 . Surface modification of Li 5 FeO 4 can slow down the formation of its by-products. For example, the existing surface modification generally mixes a lithium source, an iron source, and a modified metal together, and then obtains metal-modified Li 5 FeO 4 (CN115832471 A). On the other hand, the usual method for surface coating of Li 5 FeO 4 is to mix a lithium source, an iron source, and a carbon source, and then calcine to obtain a mixture of Li 5 FeO 4 and carbon (CN 115642232 A). These process routes for synthesizing Li 5 FeO 4 materials show simple advantages, however, the lithium supplementation performance of the materials still needs to be improved. Summary of the Invention

[0006] The purpose of the present invention is to provide a preparation method of a lithium-rich lithium ferrate composite material and its application in lithium supplementation. The lithium-rich lithium ferrate composite material is composed of lithium-rich lithium ferrate and a high-conductivity lithium-carbon compound, has the characteristics of uniform structure and excellent electrochemical performance, and excellent lithium supplementation performance.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is:

[0008] The present invention provides a preparation method of a lithium-rich lithium ferrate composite material, comprising the following steps:

[0009] (1) Mix a lithium source and an iron source with an aqueous solution of an organic compound to obtain a mixed slurry of a lithium salt, an iron salt, and an organic compound;

[0010] (2) Dry the mixed slurry obtained in step (1), and then calcine the obtained solid mixed precursor material in an inert gas environment to obtain lithium-rich lithium ferrite particles;

[0011] (3) Mix and ball-mill the lithium-rich lithium ferrite particles obtained in step (2) with a lithium source and a carbon source to obtain a composite precursor of lithium-rich lithium ferrite, a lithium salt, and a carbon source;

[0012] (4) Sinter the composite precursor obtained in step (3) in an inert environment to obtain a composite material of a carbon / lithium-carbon composite layer and lithium-rich lithium ferrite.

[0013] As a preferred technical solution, in step (1), the iron source is FeCl 2 , FeSO 4 , Fe(NO 3 ), Fe 2 O 3 , C 6 H 8 O 7 Fe, Fe(C 5 H 5 ) 2 or one or more of them.

[0014] As a preferred technical solution, in steps (1) and (3), the lithium source is Li 2 O, LiOH, Li 2 C 2 O 4 , Li 2 CO 3 , LiNO 3 or one or more of them.

[0015] As a preferred technical solution, in step (1), the organic compound is one or more of cetyltrimethylammonium bromide, polyimide, sodium dodecyl sulfate, and sodium oleate.

[0016] As a preferred technical solution, in step (1), the molar ratio of the lithium source to the iron source is 4.5 - 6:1.

[0017] As a preferred technical solution, in step (2), the calcination temperature is controlled at 400 - 1000 °C, and the heat preservation time is 2 - 36 h.

[0018] As a preferred technical solution, in step (3), the carbon source is one or more of dimethylimidazole, glucose, and starch.

[0019] As a preferred technical solution, in step (3), the molar ratio of the lithium source and the carbon source is controlled so that the lithium carbon compound obtained by sintering is L 2 C 2 、LiC、Li 4 C. Li 6 C 2 , Li 8 C 3 , Li 6 C 3 , Li 4 C 3 and Li 4 C 5 One or more of .

[0020] As a preferred technical solution, in the step (4), the sintering temperature is 300-950°C and the holding time is 0.5-36h.

[0021] The present invention also provides a lithium-rich lithium ferrate composite material prepared by the above preparation method.

[0022] The present invention also provides application of the lithium-rich lithium ferrite composite material in lithium replenishment of the positive electrode of a lithium ion battery.

[0023] Beneficial effects of the present invention:

[0024] The lithium-rich lithium ferrite composite material of the present invention comprises a lithium-carbon compound, a carbon material and lithium-rich lithium ferrite particles. The three-phase interface of the lithium-rich lithium ferrite, carbon and lithium-carbon compound particles forms a multi-layer structure. The lithium-rich lithium ferrite composite material introduces multifunctional groups through the composite of carbon and lithium-carbon compounds, increases the electronic structure of adjacent carbon atoms, accelerates charge and ion diffusion, has the characteristics of uniform structure and excellent electrochemical performance, and has excellent lithium supplementation performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a transmission electron microscope image of the lithium-rich lithium iron oxide composite material prepared in Example 1;

[0026] Figure 2 The XRD spectrum of the lithium-rich lithium iron oxide composite material prepared in Example 1;

[0027] Figure 3 The charge and discharge curve of a full battery assembled with the lithium-rich lithium iron oxide composite material prepared in Example 1 as the positive electrode material;

[0028] Figure 4 The charge and discharge curves of a full battery assembled with the lithium iron-rich lithium material prepared in Comparative Example 1 as the positive electrode material. DETAILED DESCRIPTION

[0029] To make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described below with reference to the accompanying drawings.

[0030] Example 1

[0031] (1) Lithium carbonate and iron hydroxide were mixed with an aqueous solution of cetyltrimethylammonium bromide. The molar ratio of lithium carbonate to iron hydroxide was 5.6:1, and the molar ratio of cetyltrimethylammonium bromide to lithium carbonate was 1:1, to obtain a mixed slurry of lithium salt, iron salt and organic compound;

[0032] (2) The mixed slurry obtained in step (1) was dried, and then the obtained solid mixed precursor material was calcined at 700 °C in an inert gas environment for 16 h to obtain lithium-rich lithium iron oxide particles;

[0033] (3) The lithium-rich lithium iron oxide particles obtained in step (2) were mixed and ball-milled with lithium carbonate and glucose. The mass ratio of lithium-rich lithium iron oxide particles to lithium carbonate and glucose was 99:0.5:0.5 (so that the sintered lithium-carbon compound was L 2 C 2 ), to obtain a composite precursor of lithium-rich lithium iron oxide, lithium salt and carbon source;

[0034] (4) The composite precursor obtained in step (3) was sintered at 800 °C in an inert environment for 2 h to obtain a composite material of carbon / lithium-carbon composite layer and lithium-rich lithium iron oxide.

[0035] The transmission electron microscope image of the lithium-rich lithium iron oxide composite material prepared in Example 1 is as shown in Figure 1 Figure. It can be seen from the figure that the lithium-rich lithium iron oxide composite presents amorphous granular shape, which is aggregated by small-sized particles.

[0036] The XRD spectrum of the lithium-rich lithium iron oxide composite material prepared in Example 1 is as shown in Figure 2 Figure. It can be seen from the figure that the crystal form of the prepared lithium-rich lithium iron oxide is obvious, the content of the composite material is low, and it is uniformly distributed on the lithium-rich lithium iron oxide, and no obvious crystallization peak appears.

[0037] Comparative Example 1

[0038] (1) Lithium carbonate and iron hydroxide were mixed with an aqueous solution of cetyltrimethylammonium bromide. The molar ratio of lithium carbonate to iron hydroxide was 5.6:1, and the molar ratio of cetyltrimethylammonium bromide to lithium carbonate was 1:1, to obtain a mixed slurry of lithium salt, iron salt and organic compound;

[0039] (2) The mixed slurry obtained in step (1) was dried, and then the obtained solid mixed precursor material was calcined at 700 °C in an inert gas environment for 16 h to obtain lithium-rich lithium iron oxide material.

[0040] The lithium-rich lithium ferrate composite material prepared in Example 1 and the lithium-rich lithium ferrate material prepared in Comparative Example 1 were used as the positive electrode materials respectively, and a slurry was prepared by mixing them with PVDF and acetylene black at a mass ratio of 8:1:1. The solvent of the slurry was N-methylpyrrolidone. Subsequently, the slurry was coated on an aluminum foil, and after drying, it was cut into pieces to obtain the positive electrode sheet; the negative electrode was a lithium metal sheet.

[0041] The positive electrode sheet and the negative electrode sheet of Example 1 were assembled into a coin-type full cell for charge and discharge tests, and the obtained charge and discharge curves are as Figure 3 shown; the positive electrode sheet and the negative electrode sheet of Comparative Example 1 were assembled into a coin-type full cell for charge and discharge tests, and the obtained charge and discharge curves are as Figure 4 shown; it can be seen from the figure that the lithium supplementation performance of the lithium-rich lithium ferrate material in Comparative Example 1 is much lower than that of the lithium-rich lithium ferrate composite material in Example 1.

[0042] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A preparation method of a lithium-rich lithium iron oxide composite material, characterized in that: It includes the following steps: (1) Mix a lithium source, an iron source with an aqueous solution of an organic compound to obtain a mixed slurry of a lithium salt, an iron salt and an organic compound; (2) Dry the mixed slurry obtained in step (1), and then calcine the obtained solid mixed precursor material in an inert gas environment to obtain lithium-rich lithium iron oxide particles; (3) Mix and ball-mill the lithium-rich lithium iron oxide particles obtained in step (2) with a lithium source and a carbon source to obtain a composite precursor of lithium-rich lithium iron oxide, a lithium salt and a carbon source; (4) Sinter the composite precursor obtained in step (3) in an inert environment to obtain a composite material of a carbon / lithium-carbon composite layer and lithium-rich lithium iron oxide.

2. The preparation method of the lithium-rich lithium iron oxide composite material according to claim 1, characterized in that: In the step (1), the iron source is FeCl 2 , FeSO 4 , Fe(NO 3 ), Fe 2 O 3 , C 6 H 8 O 7 Fe, Fe(C 5 H 5 ) 2 or more than one of them; in the step (1) and step (3), the lithium source is Li 2 O, LiOH, Li 2 C 2 O 4 , Li 2 CO 3 , LiNO 3 or more than one of them.

3. The preparation method of the lithium-rich lithium iron oxide composite material according to claim 1, characterized in that: In the step (1), the organic compound is one or more of cetyltrimethylammonium bromide, polyimide, sodium dodecyl sulfate, and sodium oleate.

4. The preparation method of the lithium-rich lithium iron oxide composite material according to claim 1, characterized in that: In the step (1), the molar ratio of the lithium source to the iron source is 4.5-6:

1.

5. The preparation method of the lithium-rich lithium iron oxide composite material according to claim 1, characterized in that: In the step (2), the calcination temperature is controlled at 400-1000 °C, and the heat preservation time is 2-36 h.

6. The preparation method of the lithium-rich lithium iron oxide composite material according to claim 1, characterized in that: In the step (3), the carbon source is one or more of dimethylimidazole, glucose, and starch.

7. The preparation method of the lithium-rich lithium iron oxide composite material according to claim 1, characterized in that: In the step (3), control the molar ratio of the lithium source and the carbon source so that the sintered lithium-carbon compound is one or more of L 2 C 2 , LiC, Li 4 C, Li 6 C 2 , Li 8 C 3 , Li 6 C 3 , Li 4 C 3 and Li 4 C 5 among others.

8. The preparation method of the lithium-rich lithium iron oxide composite material according to claim 1, characterized in that: In the step (4), the sintering temperature is 300-950 °C, and the heat preservation time is 0.5-36 h.

9. A lithium-rich lithium iron oxide composite material prepared by the preparation method according to any one of claims 1 to 8.

10. Application of the lithium-rich lithium iron oxide composite material according to claim 9 in lithium supplementation for the positive electrode of a lithium-ion battery.

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