Lithium iron phosphate-composite lithium manganate composite material for extracting lithium from high-altitude salt lake and preparation method of lithium iron phosphate-composite lithium manganate composite material

Abstract

The invention relates to the technical field of lithium extraction from salt lakes, in particular to a lithium iron phosphate-composite lithium manganate composite material for lithium extraction from high-altitude salt lakes and a preparation method of the lithium iron phosphate-composite lithium manganate composite material. The composite material comprises lithium iron phosphate and composite lithium manganate, wherein the composite lithium manganate comprises spinel type lithium manganate and layered lithium manganate. According to the lithium iron phosphate-composite lithium manganate composite material provided by the invention, the adopted composite lithium manganate has a three-dimensional ion conduction channel structure of spinel type lithium manganate and high specific capacity of layered lithium manganate at the same time, and the problem that a single lithium iron phosphate material is relatively poor in conductivity and ion conductivity is solved. And meanwhile, a single type of lithium manganate additive is also avoided, and the lithium extraction efficiency and the lithium extraction capacity of lithium extraction of the high-altitude salt lake are comprehensively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium extraction from salt lakes, and more specifically, to a lithium iron phosphate-lithium manganese composite oxide composite material for lithium extraction from high-altitude salt lakes and a preparation method thereof. Background Art

[0002] In recent years, with the change of the global energy structure, the importance and market share of traditional fossil energy have gradually declined, while the proportion of renewable energy has increased. The electrification level of terminal energy equipment represented by new energy vehicles has increased, correspondingly promoting the development of energy storage technologies and industries, thus posing a challenge to resource reserves. Lithium is regarded as the "white oil" of the current energy industry. The development of new energy fields such as economic growth, electric vehicles, and renewable energy storage has made lithium play an increasingly important role in economic construction and social development. The global demand for lithium reached 430,000 tons of lithium carbonate equivalent (LCE) in 2021 and is expected to reach 1.4 million to 1.7 million tons of LCE in 2030. With the continuous growth of the demand for lithium, the requirements for the development of lithium ore resources are also getting higher and higher.

[0003] At present, global lithium ore resources are mainly divided into two parts. One part exists in the form of hard ores, while a larger part exists in the form of ionic salts in salt lake brines. According to data, the total global lithium resource reserves are about 128 million tons, of which brine lithium resources account for about 59% of the global lithium resources, and more than 75% of China's lithium is stored in salt lake brines. Lithium extraction from salt lakes shows great development potential due to its outstanding advantages such as high reserves, low cost, environmental friendliness, and sustainability. In recent years, how to more efficiently extract and utilize lithium resources in salt lake brines has become the focus of research. Existing relatively mature methods for lithium extraction from salt lakes include solar pond method, extraction method, and adsorption coupling method. However, these methods are limited in development due to problems such as low production efficiency, high cost, and environmental pollution. The electrochemical lithium extraction method based on the principle of lithium-ion batteries has attracted people's attention. It has the advantages of higher lithium extraction efficiency, lower production cost, and high selectivity, thus having a wide application prospect.

[0004] The characteristics of China's salt lake lithium resources are that most of them are located in provinces such as Tibet and Qinghai. The salt lakes are geographically remote and located in high-altitude areas with harsh environments, which undoubtedly pose challenges to the current mainstream electrochemical lithium extraction material - lithium iron phosphate. This is because: firstly, the structural framework of lithium iron phosphate with an olivine structure is composed of FeO6 octahedra and PO4 3- structures. Due to the discontinuity of the FeO6 edge-sharing octahedron network in its basic structure, the electronic conductivity of lithium iron phosphate is poor; secondly, because of PO4 3-The tetrahedron restricts the volume change of the lattice. Coupled with the discontinuity of the non - continuous co - edge octahedral network structure, a good channel for continuous lithium - ion diffusion is not formed, which affects the process of lithium - ion extraction and insertion. This is manifested as a low lithium - ion diffusion rate, and it will further decrease in high - altitude and low - temperature areas during the actual application of electrochemical lithium extraction, greatly limiting its lithium - extraction efficiency. Specifically, under the working conditions of lithium extraction from high - altitude salt lakes, the extremely low temperature makes the migration, insertion, and extraction of lithium ions more difficult. At the same time, the types of cations in the salt - lake brine are rich, and the competitive insertion of impurity ions such as Na + and Mg 2+ will all affect the lithium - extraction efficiency, which poses challenges to the ionic conductivity, structural stability, and lithium - ion selectivity of the electrochemical lithium - extraction materials. Summary of the Invention

[0005] The technical problem solved by the present invention:

[0006] To solve the problem in the prior art that under the condition of lithium extraction from high - altitude salt lakes, the extremely low temperature makes the migration, insertion, and extraction of lithium ions more difficult, resulting in poor lithium - extraction efficiency.

[0007] The technical solution adopted by the present invention:

[0008] Aiming at the above - mentioned technical problems, the purpose of the present invention is to provide a lithium iron phosphate - composite lithium manganate composite material for lithium extraction from high - altitude salt lakes and its preparation method. This composite material uses commercial lithium iron phosphate as the matrix and composite lithium manganate as the additive. The composite lithium manganate is obtained by uniformly mixing spinel - type lithium manganate and layered lithium manganate through a mechanical mixing method. Then, after mixing with commercial lithium iron phosphate materials, an electrode material for electrochemical lithium extraction from high - altitude salt lakes is obtained.

[0009] Specifically,

[0010] First, the present invention provides a lithium iron phosphate - composite lithium manganate composite material for lithium extraction from high - altitude salt lakes, including lithium iron phosphate and composite lithium manganate. The composite lithium manganate includes spinel - type lithium manganate and layered lithium manganate.

[0011] According to some preferred embodiments, the mass ratio of lithium iron phosphate to composite lithium manganate is 100 - 1000:10 - 100. Among the above, in terms of the number of added parts, the number of parts of lithium iron phosphate can specifically be: 100 parts, 250 parts, 400 parts, 550 parts, 700 parts, 850 parts, 1000 parts; the number of parts of composite lithium manganate can specifically be: 10 parts, 25 parts, 40 parts, 55 parts, 70 parts, 85 parts, 100 parts.

[0012] According to some preferred embodiments, the composite lithium manganate is obtained by ball - milling spinel - type lithium manganate and layered lithium manganate.

[0013] Specifically, the preparation method of the aforementioned composite lithium manganate is as follows:

[0014] After spinel lithium manganate and layered lithium manganate are blended and then ball-milled, the obtained powder is blended with a dispersion medium, and then subjected to ultrasonic oscillation and drying to obtain composite lithium manganate.

[0015] In the above, the ratio of spinel lithium manganate to layered lithium manganate is 5 - 50:5 - 50. Specifically, in terms of the added parts, the spinel lithium manganate can be: 5 parts, 15 parts, 25 parts, 35 parts, 45 parts, 50 parts; the layered lithium manganate can be: 5 parts, 15 parts, 25 parts, 35 parts, 45 parts, 50 parts.

[0016] In the above, the rotation speed of the ball milling is 100 - 500 rpm / min. In specific implementation, it can be selected as: 100 rpm / min, 200 rpm / min, 300 rpm / min, 400 rpm / min, 500 rpm / min.

[0017] In the above, the time of the ball milling is 0.5 - 1 h. In specific implementation, it can be selected as: 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1.0 h.

[0018] In the above, the dispersion medium of the powder includes at least one of deionized water dispersion, N-methyl-2-pyrrolidone dispersion, N,N-dimethylformamide dispersion, and ethylene glycol dispersion.

[0019] In the above, the stirring rotation speed of the powder and the dispersion medium is 100 - 500 rpm / min. In specific implementation, it can be selected as: 200 rpm / min, 300 rpm / min, 400 rpm / min.

[0020] In the above, the stirring time of the powder and the dispersion medium is 2.5 - 4.5 h. In specific implementation, it can be selected as: 2.5 h, 3.0 h, 3.5 h, 4.0 h, 4.5 h.

[0021] In the above, the time of the ultrasonic oscillation is 0.5 - 1 h. In specific implementation, it can be selected as: 0.5 h, 0.6 h, 0.7 h, 0.8 h, 0.9 h, 1.0 h.

[0022] In the above, vacuum oven operation is selected for drying.

[0023] In the above, the drying temperature of the vacuum oven is 60 - 80 °C. In specific implementation, it can be selected as 60 °C, 65 °C, 70 °C, 75 °C, 80 °C.

[0024] In the above, the drying time of the vacuum oven is 12 - 18 h. Specifically, 12 h, 13 h, 14 h, 15 h, 16 h, 17 h, 18 h can be selected. The purpose is to dry the dispersion medium, and the residual mass percentage is 0.05% or less.

[0025] Second, the present invention provides a method for preparing a lithium iron phosphate - lithium composite manganese oxide composite material for extracting lithium from high - altitude salt lakes mentioned above, comprising the following steps:

[0026] Lithium iron phosphate and lithium composite manganese oxide are ball - milled to obtain a lithium iron phosphate - lithium composite manganese oxide composite material.

[0027] According to some preferred embodiments, the rotation speed of the ball - milling is 100 - 500 rpm / min.

[0028] According to some preferred embodiments, the ball - milling time is 15 - 40 min.

[0029] Beneficial effects achieved by the present invention:

[0030] (1) The lithium iron phosphate - lithium composite manganese oxide composite material provided by the present invention has good overall mixing uniformity. The average particle size of the composite material is small and uniform, and the overall specific surface area (i.e., the contact area with salt lake brine) becomes larger, effectively improving the lithium extraction efficiency. The average particle size after ball - milling treatment is about 500 nm, and the average specific surface area is 10 - 20 m 2 / g.

[0031] (2) The lithium iron phosphate - lithium composite manganese oxide composite material provided by the present invention has better adaptability to the micro - volume change during the cycle compared with single - phase spinel - type lithium manganese oxide. Therefore, mixing the two evenly as an additive can better alleviate the micro - cracks caused by the J - T effect, etc. during the cycle.

[0032] (3) The lithium iron phosphate - lithium composite manganese oxide composite material provided by the present invention uses a composite lithium manganese oxide that simultaneously has the three - dimensional ion conduction channel structure of spinel - type lithium manganese oxide and the high specific capacity of layered lithium manganese oxide, solving the problem of poor conductivity and ion conductivity of a single lithium iron phosphate material. At the same time, it also avoids a single type of lithium manganese oxide additive, comprehensively improving the lithium extraction efficiency and lithium extraction capacity for extracting lithium from high - altitude salt lakes.

[0033] (4) The preparation method provided by the present invention is simple in operation. Only by mechanically compounding spinel - type lithium manganese oxide and layered lithium manganese oxide and adjusting the mass ratio of different crystal forms of lithium manganese oxide, it can be used as an additive with excellent performance and added to lithium iron phosphate, thereby effectively improving the performance of the composite material as an electrochemical lithium extraction electrode material, and further better used for lithium extraction from salt lakes to improve the lithium extraction efficiency. Description of the Drawings

[0034] Figure 1 Graph showing the lithium extraction cycle stability and charge-discharge efficiency of the lithium iron phosphate electrode materials obtained in Example 1 and Comparative Example 1;

[0035] Figure 2 Voltage-capacity curve of the lithium iron phosphate electrode material obtained in Comparative Example 1;

[0036] Figure 3 Voltage-capacity curve of the lithium iron phosphate electrode material obtained in Example 1. Detailed implementation manners

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. For those not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0038] Example 1

[0039] In this example, the lithium iron phosphate-lithium manganese composite oxide composite material for lithium extraction from high-altitude salt lakes is prepared through the following steps:

[0040] (1) Take 40 g of spinel-type lithium manganese oxide, add 10 g of layered lithium manganese oxide thereto, and ball-mill and mix them at a speed of 200 rpm for 1.5 hours;

[0041] (2) Add the powder obtained by ball-milling in step (1) to an N-methyl-2-pyrrolidone dispersion liquid, stir and mix it at a speed of 300 rpm under vacuum and at room temperature for 4 hours, and perform ultrasonic oscillation for 0.5 hour;

[0042] (3) Dry the mixed dispersion liquid obtained in step (2) in a vacuum oven at 75 °C to obtain lithium manganese composite oxide powder;

[0043] (4) Take 500 g of commercial lithium iron phosphate, add 50 g of the lithium manganese composite oxide powder obtained in step (3) thereto, and ball-mill at a speed of 300 rpm under vacuum and at room temperature for 1 hour to obtain a lithium iron phosphate-lithium manganese composite oxide composite material.

[0044] Example 2

[0045] This example is basically the same as Example 1, except that in step (1), the ball-milling speed is 300 rpm, and the rest are the same settings.

[0046] Example 3

[0047] This example is basically the same as Example 1, except that in step (1), the ball milling speed is 400 rpm / min, and the rest are the same settings.

[0048] Example 4

[0049] This example is basically the same as Example 1, except that in step (1), the ball milling mixing time is 0.5 hours, and the rest are the same settings.

[0050] Example 5

[0051] This example is basically the same as Example 1, except that in step (1), the ball milling mixing time is 1 hour, and the rest are the same settings.

[0052] Example 6

[0053] This example is basically the same as Example 1, except that in step (5), the ball milling mixing time is 1.5 hours, and the rest are the same settings.

[0054] Example 7

[0055] This example is basically the same as Example 1, except that in step (1), the mass of spinel-type lithium manganate taken is 35 g, and the mass of layered lithium manganate added is 15 g, and the rest are the same settings.

[0056] Example 8

[0057] This example is basically the same as Example 1, except that in step (1), the mass of spinel-type lithium manganate taken is 30 g, and the mass of layered lithium manganate added is 20 g, and the rest are the same settings.

[0058] Example 9

[0059] This example is basically the same as Example 1, except that in step (1), the mass of spinel-type lithium manganate taken is 25 g, and the mass of layered lithium manganate added is 25 g, and the rest are the same settings.

[0060] Comparative Example 1

[0061] The difference between this comparative example and Example 1 is that Comparative Example 1 directly uses commercial lithium iron phosphate and applies it to lithium extraction from salt lakes.

[0062] Comparative Example 2

[0063] The difference between this comparative example and Example 1 is that Comparative Example 2 uses single spinel lithium manganate + lithium iron phosphate and applies it to lithium extraction from salt lakes.

[0064] Comparative Example 3

[0065] The difference between this comparative example and Example 1 is that in Comparative Example 3, single-layer lithium manganate + lithium iron phosphate is used for lithium extraction from salt lakes.

[0066] Test Example

[0067] The samples prepared in Examples 1-9 and Comparative Examples 1-3 were used to measure the performance of the lithium iron phosphate electrode material. The specific method is as follows: After thoroughly grinding 500 g of the lithium iron phosphate-lithium composite manganate composite material, it is mixed evenly with super C65 conductive agent and polyvinylidene fluoride in a mass ratio of 80:10:10, and then coated on a titanium mesh current collector with a coating thickness of 250 μm. It is dried at 80 °C for 12 h, and then cut into a pole piece with a diameter of 2 * 2 cm as the working electrode. After thoroughly grinding the delithiated lithium iron phosphate-lithium composite manganate composite material with the same mass that has been electrochemically treated in advance, it is also mixed evenly with super C65 conductive agent and polyvinylidene fluoride in a mass ratio of 80:10:10, and then coated on a titanium mesh current collector with a coating thickness of 250 μm. It is dried at 80 °C for 12 h, and then cut into a pole piece with a diameter of 2 * 2 cm as the counter electrode. The working electrode, counter electrode, and anion separator are assembled into a battery, and a lithium ion insertion / extraction experiment is carried out at a current density of 1C at 5 °C. The experimental results are shown in Table 1.

[0068] The comparison results of the lithium extraction cycle stability and charge-discharge efficiency of the samples obtained in Example 1 and Comparative Document 1 are as Figure 1 shown.

[0069] The voltage-capacity curve diagram of the sample obtained in Comparative Example 1 is as Figure 2 shown.

[0070] The voltage-capacity curve diagram of the sample obtained in Example 1 is as Figure 3 shown.

[0071] Table 1 Measurement Results

[0072]

[0073] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, various modifications and changes can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A lithium iron phosphate-lithium manganese composite oxide composite material for extracting lithium from high-altitude salt lakes, characterized in that, It includes lithium iron phosphate and composite lithium manganate, and the composite lithium manganate includes spinel-type lithium manganate and layered lithium manganate.

2. The lithium iron phosphate-lithium composite manganese oxide composite material for extracting lithium from high-altitude salt lakes according to claim 1, wherein The mass ratio of lithium iron phosphate to composite lithium manganate is 100 - 1000:10 - 100.

3. The lithium iron phosphate-lithium composite manganese oxide composite material for extracting lithium from high-altitude salt lakes according to claim 1, characterized in that, The composite lithium manganate is obtained by ball-milling spinel-type lithium manganate and layered lithium manganate.

4. The lithium iron phosphate-lithium composite manganese oxide composite material for extracting lithium from high-altitude salt lakes according to claim 3, characterized in that, After spinel-type lithium manganate and layered lithium manganate are blended, and then ball-milled, the obtained powder is blended with a dispersion medium, and then through ultrasonic oscillation and drying, the composite lithium manganate is obtained.

5. The lithium iron phosphate-lithium composite manganese oxide composite material for extracting lithium from high-altitude salt lakes according to claim 4, wherein The rotation speed of the ball-milling is 100 - 500 rpm / min; and / or, the time of the ball-milling is 0.5 - 1 h.

6. The lithium iron phosphate-lithium composite manganese oxide composite material for extracting lithium from high-altitude salt lakes according to claim 4, wherein The dispersion medium includes at least one of deionized water dispersion, N-methyl-2-pyrrolidone dispersion, N,N-dimethylformamide dispersion, and ethylene glycol dispersion.

7. The lithium iron phosphate-lithium composite manganese oxide composite material for extracting lithium from high-altitude salt lakes according to claim 4, characterized in that The stirring rotation speed of the powder and the dispersion medium is 100 - 500 rpm / min; and / or, the stirring time of the powder and the dispersion medium is 2.5 - 4.5 h; and / or, the time of the ultrasonic oscillation is 0.5 - 1 h; and / or, the drying temperature is 75 - 85 °C.

8. A lithium iron phosphate-lithium composite manganese oxide composite material for extracting lithium from high-altitude salt lakes according to any one of claims 1 to 7, characterized in that, The mass ratio of spinel-type lithium manganate to layered lithium manganate is 5 - 50:5 - 50.

9. A method for preparing a lithium iron phosphate-lithium manganese composite oxide composite material for extracting lithium from high-altitude salt lakes according to any one of claims 1 to 8, characterized in that, It includes the following steps: Lithium iron phosphate and composite lithium manganate are ball-milled to obtain a lithium iron phosphate-composite lithium manganate composite material.

10. The preparation method of the lithium iron phosphate-lithium composite manganese oxide composite material for extracting lithium from high-altitude salt lakes according to claim 9, characterized in that, The rotation speed of the ball-milling is 100 - 500 rpm / min; and / or, the time of the ball-milling is 15 - 40 min.

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