A method and separation device for reducing the iron phosphide content in lithium iron phosphate cathode material

Abstract

This invention discloses a method and separation device for reducing the iron phosphide content in lithium iron phosphate cathode materials. The invention utilizes a centrifugal separation device to separate iron phosphide from lithium iron phosphate materials containing iron phosphide, solving the industry problem of uncontrollable iron phosphide content in high-compact lithium iron phosphate cathode powder products. It provides a practical and effective separation method for material production and sales; offers technical support for the separation of iron phosphide and lithium iron phosphate; and allows for the separate sale of lithium iron phosphate and iron phosphide produced in battery factories, increasing profits. Furthermore, the separation process is easy to operate, does not require high-temperature control, reduces production costs, and improves operability.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a method and separation device for reducing the iron phosphide content in lithium iron phosphate cathode material. Background Technology

[0002] As lithium-ion batteries continue to evolve, higher capacity and greater safety have become the pursuit of product excellence. Lithium iron phosphate (LFP) is widely used in lithium-ion batteries due to its excellent safety, high thermal stability, and low susceptibility to thermal runaway. Furthermore, LFP also exhibits good charge / discharge performance and rate capability, meeting the needs of various application scenarios. These advantages make LFP one of the most important cathode materials in the current lithium-ion battery field.

[0003] Driven by the demand for high energy density, lithium iron phosphate (LFP) also requires further improvement in material compaction performance. A common industry approach is to increase the sintering temperature during the sintering process; however, lithium iron phosphate powder will generate iron phosphide (FeP) under high-temperature reducing atmospheres. As a magnetic material, iron phosphide affects battery life, making battery manufacturers reluctant to purchase lithium iron phosphate materials containing iron phosphide. Material manufacturers also lack effective methods to improve material compaction without iron phosphide formation. Furthermore, the price of iron phosphide monomers is significantly higher than that of lithium iron phosphate (iron phosphide: RMB 4526.0 / 10g, lithium iron phosphate: RMB 42300.0 / ton). Therefore, it is necessary to propose an effective method for separating iron phosphide from lithium iron phosphate. Summary of the Invention

[0004] The present invention aims to at least partially solve one of the technical problems in the related art.

[0005] Therefore, embodiments of the present invention provide a method and separation device for reducing the iron phosphide content in lithium iron phosphate cathode material.

[0006] In a first aspect, the present invention proposes a method for reducing the iron phosphide content in lithium iron phosphate cathode material, comprising the following steps:

[0007] The sintered lithium iron phosphate is placed in a separation device;

[0008] The upper layer of iron phosphide was separated by centrifugation under vacuum conditions.

[0009] Furthermore, the centrifugation speed is 5000–16000 r / min, and the centrifugation time is 0.5–4 h.

[0010] On the other hand, the present invention provides a separation apparatus for implementing the method proposed in the first aspect above, comprising:

[0011] The inner furnace wall has multiple openable and closable wire hole structures arranged along the circumferential direction.

[0012] An outer furnace wall is fitted over the inner furnace wall, and a hollow structure is formed between the inner furnace wall and the outer furnace wall.

[0013] A collection box is located below the outer furnace wall.

[0014] Furthermore, the inner furnace wall is used to provide a centrifugal environment, and the outer furnace wall is used to receive materials separated from the inner furnace wall.

[0015] Furthermore, the collection box is used to collect material flowing out from the lower opening of the outer furnace wall.

[0016] Furthermore, the wire hole structure includes an arc-shaped pin and an arc-shaped slot, wherein the arc-shaped pin can be inserted into or protrude from the arc-shaped slot.

[0017] Furthermore, the position and number of openings in the wire hole structure are determined based on the amount of material added.

[0018] Furthermore, it also includes a controller for controlling and adjusting the rotational speed and separation time of the inner furnace wall.

[0019] Furthermore, the collection box is detachably connected to the outer furnace wall.

[0020] Furthermore, both the inner and outer furnace walls are made of high-strength, wear-resistant materials.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] This invention utilizes a centrifugal separation device to separate iron phosphide from lithium iron phosphate materials containing iron phosphide, solving the industry's problem of uncontrollable iron phosphide content in high-pressure compaction lithium iron phosphate powder products. It provides a practical and effective separation method for material production and sales, offering technical support for the separation of iron phosphide and lithium iron phosphate. Separating lithium iron phosphate and iron phosphide produced in battery factories for separate sales increases profits, and the separation process is easy to operate, requires no high-temperature control, reduces production costs, and improves operability. Attached Figure Description

[0023] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments taken in conjunction with the accompanying drawings, wherein:

[0024] Figure 1 This is a schematic diagram of the separation device of the present invention;

[0025] Figure 2This is a schematic diagram of the wire hole structure of the present invention;

[0026] Figure 3 These are electron microscope images of lithium iron phosphate before and after centrifugation in Example 1 of the present invention;

[0027] Figure 4 The image shows the XRD pattern of the iron phosphide isolated in Example 1 of this invention.

[0028] Figure 5 This is a schematic diagram showing the mass ratio of iron phosphide and lithium iron phosphate in the iron phosphide separated in Example 1 of the present invention;

[0029] Figure 6 This is a schematic diagram showing the mass ratio of iron phosphide and lithium iron phosphate in the sintered lithium iron phosphate after Example 1 of the present invention. Detailed Implementation

[0030] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0031] The following describes, with reference to the accompanying drawings, a method and separation apparatus for reducing the iron phosphide content in lithium iron phosphate cathode material according to embodiments of the present invention.

[0032] like Figure 1 and 2 As shown, the separation device of the present invention is a double-layer high-speed separation furnace, including an inner furnace wall, an outer furnace wall, a collection box, and control devices.

[0033] The inner furnace wall, located on the inside, provides a high-speed centrifugal environment, allowing materials to separate under centrifugal force. A closable feed port is located at the top of the inner furnace wall, through which materials requiring centrifugal separation are added. Multiple closable perforated structures are arranged along the circumference of the furnace body on the inner furnace wall, with these perforated structures positioned vertically along the furnace body.

[0034] The wire hole structure includes an arc-shaped pin and an arc-shaped slot, wherein the arc-shaped pin can be inserted into or protrude from the arc-shaped slot. It is understood that when the arc-shaped pin is inserted into the arc-shaped slot, the wire hole structure is closed, and material cannot flow out of the wire hole structure; when the arc-shaped pin protrudes from the arc-shaped slot, the wire hole structure is open, and material can flow out of the wire hole structure.

[0035] The location and number of openings in the wire hole structure are determined based on the amount of material added. It can be understood that when the material is added to the inner furnace wall, the material fills upward along the bottom of the inner furnace wall, and the openings in the wire hole structure are located above the material.

[0036] In some embodiments, the arc pin is connected to an automatic control device to automatically control the insertion or extension of the arc pin.

[0037] The outer furnace wall is fitted outside the inner furnace wall. The outer furnace wall is used to receive the material separated from the inner furnace wall. There is a certain distance between the inner furnace wall and the outer furnace wall, so that a hollow structure is formed between the inner furnace wall and the outer furnace wall. The material separated from the inner furnace wall by centrifugation flows into the hollow space between the two furnace walls through the wire hole structure.

[0038] In some embodiments, both the inner and outer furnace walls are made of high-strength, wear-resistant materials to maintain the stability and durability of the furnace body, extend its service life, and reduce maintenance costs.

[0039] The collection box is located below the outer furnace wall and is used to collect the material flowing out from the lower opening of the outer furnace wall.

[0040] In some embodiments, the collection box is detachably connected to the outer furnace wall. After centrifugal separation is completed, the double-layer separator is shut down, the collection box is removed, and the collected material is taken out.

[0041] A sealed space can be formed between the inner furnace wall, the outer furnace wall, and the collection box to achieve centrifugal separation under vacuum conditions in some embodiments. The purpose of vacuuming is to prevent the material from reacting with air and to prevent the mixing of other foreign impurities.

[0042] The controller is used to control and adjust the rotation speed and separation time of the inner furnace wall. It can automatically adjust the dispersion speed and separation time of the inner furnace wall without manual intervention, which greatly improves the operating efficiency and reduces the operating difficulty. At the same time, the automatic control system can also adjust the separation parameters according to actual needs to adapt to the separation requirements of different types of powders.

[0043] A method for reducing the iron phosphide content in lithium iron phosphate cathode material, using the separation device of the present invention, includes the following steps: placing sintered lithium iron phosphate in the separation device; and centrifuging to separate the upper layer of iron phosphide under vacuum conditions.

[0044] Specifically, the aforementioned separation device is used to separate iron phosphide from sintered lithium iron phosphate to reduce the iron phosphide content in the cathode material. A certain amount of sintered lithium iron phosphate is added to the inner furnace wall. Based on the amount of lithium iron phosphate added, some of the perforated structures are opened. The centrifugal speed and centrifugation time are set, and the double-layer separation furnace is turned on. Under centrifugal force, the lithium iron phosphate powder separates and separates into layers. The iron phosphide in the upper layer flows out through the opened perforated structure into the outer furnace wall and falls into the collection box. After centrifugation, the double-layer separation furnace is closed, and the collection box is removed to obtain material whose main component is iron phosphide.

[0045] Additionally, it is understandable that sintering is a commonly used process to improve the compaction performance of lithium iron phosphate, so it will not be discussed in detail here.

[0046] In some embodiments, the centrifugation speed is 5000–16000 r / min, and the centrifugation time is 0.5–4 h. The centrifugation speed can be 5000 r / min, 8000 r / min, 10000 r / min, 13000 r / min, 16000 r / min, or any combination of two values, and the centrifugation time can be 0.5 h, 2 h, 2.5 h, 3 h, 3.5 h, 4 h, or any combination of two values. It is understood that the centrifugation time is determined according to the degree of iron phosphide to be separated; that is, the longer the separation time, the lower the iron phosphide content in the cathode material. However, with a longer centrifugation time, some lithium iron phosphate powder will be lost; a shorter centrifugation time will not achieve the desired effect. Therefore, the centrifugation time needs to be selected according to the requirements.

[0047] The main component of the material collected in the collection box is iron phosphide. Iron phosphide has a high value and can be collected and sold to increase profits.

[0048] The present invention will now be described with reference to specific embodiments.

[0049] Example 1

[0050] The double-layer separator furnace has inner and outer walls. The inner wall has a diameter of 50cm and a height of 100cm, and is made of high-strength, wear-resistant stainless steel. It features seven perforated sections. The outer wall has a diameter of 60cm and a height of 120cm, and is made of high-temperature resistant, corrosion-resistant ceramic. A 5cm gap is maintained between the two walls to facilitate the separation and collection of powder.

[0051] Add 3 kg of sintered lithium iron phosphate with a particle size range of 0.1-1 mm to the inner furnace wall, open the wire hole structure above the lithium iron phosphate material, set the rotation speed of the inner furnace wall to 6000 r / min, the centrifugation time to 1 h, and start the double-layer separation furnace after vacuuming.

[0052] After centrifugation is complete, shut down the double-layer separator, disassemble the collection box, and remove the separated material to complete the separation process.

[0053] Example 2

[0054] The double-layer separator furnace has inner and outer walls. The inner wall has a diameter of 50cm and a height of 100cm, and is made of high-strength, wear-resistant stainless steel. It features seven perforated sections. The outer wall has a diameter of 60cm and a height of 120cm, and is made of high-temperature resistant, corrosion-resistant ceramic. A 5cm gap is maintained between the two walls to facilitate the separation and collection of powder.

[0055] 4 kg of sintered lithium iron phosphate with a particle size range of 0.1-1 mm was added to the inner furnace wall. The wire hole structure above the lithium iron phosphate material was opened. The rotation speed of the inner furnace wall was set to 10,000 r / min and the centrifugation time was 2 h. After vacuuming, the double-layer separation furnace was opened.

[0056] After centrifugation is complete, shut down the double-layer separator, disassemble the collection box, and remove the separated material to complete the separation process.

[0057] Example 3

[0058] The double-layer separator furnace has inner and outer walls. The inner wall has a diameter of 50cm and a height of 100cm, and is made of high-strength, wear-resistant stainless steel. It features seven perforated sections. The outer wall has a diameter of 60cm and a height of 120cm, and is made of high-temperature resistant, corrosion-resistant ceramic. A 5cm gap is maintained between the two walls to facilitate the separation and collection of powder.

[0059] 5 kg of sintered lithium iron phosphate with a particle size range of 0.1-1 mm was added to the inner furnace wall. The wire hole structure above the lithium iron phosphate material was opened. The rotation speed of the inner furnace wall was set to 12000 r / min and the centrifugation time was 3 h. After vacuuming, the double-layer separation furnace was opened.

[0060] After centrifugation is complete, shut down the double-layer separator, disassemble the collection box, and remove the separated material to complete the separation process.

[0061] Test Example 1

[0062] The material from Example 1 was subjected to scanning electron microscopy (Zeiss scanning electron microscope), and the test results are as follows: Figure 3 As shown. From Figure 3 It can be seen that before separation, small lithium iron phosphate particles were attached to iron phosphide. After separation, the iron phosphide was separated out, and the small lithium iron phosphate particles fell off to form a uniform material layer.

[0063] Test Example 2

[0064] The material separated in Example 1 was subjected to XRD testing, and the content of iron phosphide in the sample was quantitatively determined. The test results are as follows: Figure 4 and Figure 5As shown. ICP-OES was used for testing. The samples underwent a two-stage digestion process to test the iron phosphide content. The iron phosphide content in the sintered lithium iron phosphate from Example 1 was tested, and the results are shown below. Figure 6 As shown.

[0065] from Figure 4 The XRD pattern qualitatively revealed the presence of iron phosphide in the separated material. Figure 5 It can be seen that iron phosphide accounts for more than 65% of the separated material. (Compared to...) Figure 6 The comparison of the actual iron phosphide content in the sintered lithium iron phosphate sample shows that the iron phosphide in lithium iron phosphate has been enriched and separated.

[0066] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms may refer to different embodiments or examples. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0067] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0068] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A method for reducing the iron phosphide content in lithium iron phosphate cathode material, characterized in that, Includes the following steps: The sintered lithium iron phosphate is placed in a separation device; The upper layer of iron phosphide was separated by centrifugation under vacuum conditions. The method is carried out using a separation device, the separation device comprising: The inner furnace wall has multiple openable and closable wire hole structures arranged along the circumferential direction. An outer furnace wall is fitted over the inner furnace wall, and a hollow structure is formed between the inner and outer furnace walls. The inner furnace wall is used to provide a centrifugal environment, and the outer furnace wall is used to receive materials separated from the inner furnace wall. A collection box is located below the outer furnace wall.

2. The method as described in claim 1, characterized in that, The centrifugation speed is 5000-16000 r / min, and the centrifugation time is 0.5-4 h.

3. The method as described in claim 1, characterized in that, The collection box is used to collect the material flowing out from the lower opening of the outer furnace wall.

4. The method as described in claim 1, characterized in that, The wire hole structure includes an arc-shaped pin and an arc-shaped slot, wherein the arc-shaped pin can be inserted into or protrude from the arc-shaped slot.

5. The method as described in claim 4, characterized in that, The location and number of openings in the wire hole structure are determined based on the amount of material added.

6. The method as described in claim 1, characterized in that, It also includes a controller for controlling and adjusting the rotational speed and separation time of the inner furnace wall.

7. The method as described in claim 1, characterized in that, The collection box is detachably connected to the outer furnace wall.

8. The method as described in claim 1, characterized in that, Both the inner and outer furnace walls are made of high-strength, wear-resistant materials.

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