Method for reducing content of iron phosphide in positive electrode material lithium iron phosphate and separation device

Abstract

The invention discloses a method for reducing the content of iron phosphide in a positive electrode material lithium iron phosphate and a separation device. According to the method, the centrifugal separation device is used for separating out iron phosphide in the lithium iron phosphate material containing iron phosphide, and the problem that the content of iron phosphide in a high-compaction positive electrode lithium iron phosphate powder product cannot be controlled in the industry is solved; a practical and effective separation method is provided for material production and material sales; technical support is provided for separation of iron phosphide and lithium iron phosphate; lithium iron phosphate and iron phosphide produced in a battery plant are separated and then sold separately, the income is improved, the separation process is easy to operate, high-temperature control is not needed, the production cost is reduced, and the operability is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to a method for reducing the content of iron phosphide in lithium iron phosphate, a positive electrode material, and a separation device. Background Art

[0002] As lithium-ion batteries continue to develop, higher capacity and greater safety have become the direction of product pursuit. Lithium iron phosphate is widely used in lithium-ion batteries because of its excellent safety, high thermal stability, and low risk of thermal runaway. In addition, lithium iron phosphate also has good charge and discharge performance and rate performance, which can meet the needs of various application scenarios. These advantages make lithium iron phosphate one of the important positive electrode materials in the current lithium-ion battery field.

[0003] Driven by the demand for high energy density, lithium iron phosphate (LFP) also needs to further improve the compaction performance of the material. The common method in the industry is to increase the sintering temperature during the sintering production process, but lithium iron phosphate powder will generate iron phosphide (FeP) under a high-temperature reducing atmosphere. As a magnetic material, iron phosphide has an impact on the life of the battery, which makes battery manufacturers reluctant to purchase lithium iron phosphate materials containing iron phosphide, and material manufacturers have no good way to improve the compaction of the material without generating iron phosphide. In addition, the selling price of iron phosphide monomer is much higher than that of lithium iron phosphate (iron phosphide: 4526.0 yuan / 10g, lithium iron phosphate: 42300.0 yuan / ton). Therefore, it is necessary to propose a method for effectively separating iron phosphide from lithium iron phosphate. Summary of the invention

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

[0005] To this end, an embodiment of the present invention provides a method and a separation device for reducing the content of iron phosphide in lithium iron phosphate, a positive electrode material.

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

[0007] placing the sintered lithium iron phosphate in a separation device;

[0008] The iron phosphide in the upper layer is separated by centrifugation under vacuum conditions.

[0009] Furthermore, the rotation speed of the centrifugal separation is 5000-16000 r / min, and the centrifugal time is 0.5-4 h.

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

[0011] An inner furnace wall, wherein a plurality of openable and closable linear hole structures are arranged on the inner furnace wall along a circumferential direction;

[0012] An outer furnace wall, wherein the outer furnace wall is sleeved outside the inner furnace wall, and a hollow structure is formed between the inner furnace wall and the outer furnace wall;

[0013] A collecting box is arranged 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 collecting box is used to collect materials 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, and the arc-shaped pin can be inserted into or extended from the arc-shaped slot.

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

[0018] Furthermore, it also includes a controller, which is used to control and adjust the rotation speed and separation time of the inner furnace wall.

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

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

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

[0022] The present invention utilizes a centrifugal separation device to separate the iron phosphide from the lithium iron phosphate material containing the iron phosphide, thereby solving the problem in the industry that the iron phosphide content in the high-pressure compacted positive lithium iron phosphate powder product cannot be controlled; provides a practical and effective separation method for material production and material sales; provides technical support for the separation of iron phosphide and lithium iron phosphate; separates the lithium iron phosphate and the iron phosphide produced in the battery factory and sells them separately, thereby increasing the profit; and the separation process is easy to operate, does not require high-temperature control, reduces the production cost, and improves the operability. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

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

[0026] Figure 3 The electron microscope images of lithium iron phosphate before and after centrifugal separation in Example 1 of the present invention are shown;

[0027] Figure 4 This is the XRD diagram of the iron phosphide separated in Example 1 of the present invention;

[0028] Figure 5 This is a schematic diagram of 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 of the mass ratio of iron phosphide and lithium iron phosphate in the lithium iron phosphate after sintering in Example 1 of the present invention. DETAILED DESCRIPTION

[0030] Embodiments of the present invention are described in detail below, 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 should not be construed as limiting the present invention.

[0031] The following describes a method and a separation device for reducing the iron phosphide content in the positive electrode material lithium iron phosphate according to an embodiment of the present invention with reference to the accompanying drawings.

[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 collecting box and a control device.

[0033] The inner furnace wall is located on the inner side and is used to provide a high-speed rotating centrifugal environment so that the materials can be separated under the action of centrifugal force. A closable feeding port is provided on the upper part of the inner furnace wall, and the materials to be centrifugally separated are added into the inner furnace wall from the feeding port. A plurality of openable and closable wire hole structures are provided on the inner furnace wall along the circumferential direction of the furnace body, and the plurality of wire hole structures are provided along the upper and lower positions of the furnace body.

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

[0035] The position and number of the opened wire hole structure are determined according to the amount of material added. It can be understood that when the material is added to the inner furnace wall, the material is filled upward along the bottom of the inner furnace wall, and the position of the opened wire hole structure is 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 sleeved on the outside of the inner furnace wall. The outer furnace wall is used to receive the materials 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 materials centrifugally separated from the inner furnace wall flow into the hollow space between the two furnace walls through the linear hole structure.

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

[0039] The collecting box is arranged below the outer furnace wall and is used for collecting materials flowing out from the lower opening of the outer furnace wall.

[0040] In some embodiments, the collecting box is detachably connected to the outer furnace wall. After the centrifugal separation is completed, the double-layer separation furnace is closed, the collecting box is removed, and the collected materials are taken out.

[0041] A closed space may 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] The method for reducing the iron phosphide content in lithium iron phosphate, a positive electrode material, uses the separation device of the present invention, and comprises the following steps: placing the sintered lithium iron phosphate in the separation device; and centrifugally separating the upper layer of iron phosphide under vacuum conditions.

[0044] Specifically, the above-mentioned separation device is used to separate the iron phosphide in the sintered lithium iron phosphate to reduce the content of iron phosphide in the positive electrode material lithium iron phosphate. A certain amount of sintered lithium iron phosphate is added to the inner furnace wall, and part of the wire hole structure is opened according to the amount of lithium iron phosphate added, the speed and centrifugal separation time are set, and the double-layer separation furnace is opened. Under the action of centrifugal force, the lithium iron phosphate powder is separated and layered, and the iron phosphide in the upper layer flows out from the opened wire hole structure into the outer furnace wall and falls into the collection box. After the centrifugation is completed, the double-layer separation furnace is closed, and the collection box is disassembled to obtain a material whose main component is iron phosphide.

[0045] In addition, it can be understood that the sintering process is a commonly used process for improving the compaction performance of lithium iron phosphate, and will not be introduced in detail here.

[0046] In some embodiments, the speed of centrifugal separation is 5000-16000r / min, and the centrifugal time is 0.5-4h. The speed of centrifugal separation can be 5000r / min, 8000r / min, 10000r / min, 13000r / min, 16000r / min or a value within the range of any two values, and the centrifugal time can be 0.5h, 2h, 2.5h, 3h, 3.5h, 4h or a value within the range of any two values. It can be understood that the time of centrifugal separation is determined according to the degree of iron phosphide to be separated, that is, the longer the separation time, the lower the content of iron phosphide in the positive electrode material. However, when the centrifugal time is long, a part of the lithium iron phosphate powder will also be lost; if the centrifugal time is short, the effect cannot be achieved. Therefore, the centrifugal time needs to be selected according to the needs.

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

[0048] The present invention is described below with reference to specific embodiments.

[0049] Example 1

[0050] The double-layer separation furnace has two layers of inner and outer furnace walls. The inner furnace wall has a diameter of 50cm and a height of 100cm. It is made of high-strength, wear-resistant stainless steel. There are 7 wire hole structures on the inner furnace wall. The outer furnace has a diameter of 60cm and a height of 120cm. It is made of high-temperature and corrosion-resistant ceramics. There is a 5cm gap between the two layers of the furnace to facilitate the separation and collection of powder.

[0051] 3 kg of sintered lithium iron phosphate with a particle size range of 0.1 to 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 6000 r / min, the centrifugal time was 1 hour, and the double-layer separation furnace was opened after vacuuming.

[0052] After centrifugation is completed, the double-layer separation furnace is closed, the collection box is disassembled, and the separated materials are taken out to complete the separation process.

[0053] Example 2

[0054] The double-layer separation furnace has two layers of inner and outer furnace walls. The inner furnace wall has a diameter of 50cm and a height of 100cm. It is made of high-strength, wear-resistant stainless steel. There are 7 wire hole structures on the inner furnace wall. The outer furnace has a diameter of 60cm and a height of 120cm. It is made of high-temperature and corrosion-resistant ceramics. There is a 5cm gap between the two layers of the furnace to facilitate the separation and collection of powder.

[0055] 4 kg of sintered lithium iron phosphate with a particle size range of 0.1 to 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, the centrifugal time was 2 h, and the double-layer separation furnace was opened after vacuuming.

[0056] After centrifugation is completed, the double-layer separation furnace is closed, the collection box is disassembled, and the separated materials are taken out to complete the separation process.

[0057] Example 3

[0058] The double-layer separation furnace has two layers of inner and outer furnace walls. The inner furnace wall has a diameter of 50cm and a height of 100cm. It is made of high-strength, wear-resistant stainless steel. There are 7 wire hole structures on the inner furnace wall. The outer furnace has a diameter of 60cm and a height of 120cm. It is made of high-temperature and corrosion-resistant ceramics. There is a 5cm gap between the two layers of the furnace to facilitate the separation and collection of powder.

[0059] 5 kg of sintered lithium iron phosphate with a particle size range of 0.1 to 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, the centrifugation time was 3 h, and the double-layer separation furnace was opened after vacuuming.

[0060] After centrifugation is completed, the double-layer separation furnace is closed, the collection box is disassembled, and the separated materials are taken out to complete the separation process.

[0061] Test Example 1

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

[0063] Test Example 2

[0064] The material separated from Example 1 was subjected to XRD test and the content of iron phosphide in the sample was quantitatively tested. The test results are as follows: Figure 4 and Figure 5Using ICP-OES test, the sample was treated by secondary digestion to test the single iron phosphide content. The content of iron phosphide in the lithium iron phosphate after sintering in Example 1 was tested. The test results are as follows Figure 6 shown.

[0065] from Figure 4 The XRD spectrum shows that the separated material contains iron phosphide. Figure 5 It can be seen that the proportion of iron phosphide in the separated material is more than 65%. Figure 6 Compared with the actual iron phosphide content in the lithium iron phosphate sample after sintering, it can be seen that the iron phosphide in the lithium iron phosphate is enriched and separated.

[0066] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms may be for different embodiments or examples. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, unless they are contradictory.

[0067] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

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

Claims

1. A method for reducing the content of iron phosphide in lithium iron phosphate, a positive electrode material, characterized in that: The following steps are involved: placing the sintered lithium iron phosphate in a separation device; The iron phosphide in the upper layer is separated by centrifugation under vacuum conditions.

2. The method according to claim 1, characterized in that The rotation speed of the centrifugal separation is 5000-16000 r / min, and the centrifugal time is 0.5-4 h.

3. A separation device, characterized in that: The method for implementing claim 1 or 2 comprises: An inner furnace wall, wherein a plurality of openable and closable linear hole structures are arranged on the inner furnace wall along a circumferential direction; An outer furnace wall, wherein the outer furnace wall is sleeved outside the inner furnace wall, and a hollow structure is formed between the inner furnace wall and the outer furnace wall; A collecting box is arranged below the outer furnace wall.

4. The separation device according to claim 3, characterized in that 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.

5. The separation device according to claim 3, characterized in that: The collecting box is used to collect materials flowing out from the lower opening of the outer furnace wall.

6. The separation device according to claim 3, characterized in that: The wire hole structure comprises an arc-shaped pin and an arc-shaped slot, and the arc-shaped pin can be inserted into or extended out of the arc-shaped slot.

7. The separation device according to claim 6, characterized in that The position and number of openings of the wire hole structure are determined according to the amount of material added.

8. The separation device according to claim 3, characterized in that: It also includes a controller, which is used to control and adjust the rotation speed and separation time of the inner furnace wall.

9. The separation device according to claim 3, characterized in that: The collecting box is detachably connected to the outer furnace wall.

10. The separation device according to claim 3, characterized in that: The inner furnace wall and the outer furnace wall are both made of high-strength and wear-resistant materials.

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