Method for eliminating flocculent carbon in lithium iron phosphate

Abstract

The application discloses a method for eliminating flocculent carbon in lithium iron phosphate, which comprises the following steps: putting lithium iron phosphate raw materials into a microwave heating device, setting the power of the microwave to 700-900 W, setting the frequency to 2.45 GHz, simultaneously introducing carbon dioxide gas with a flow rate of 1 L / min, and then heating for 30-60 min. The method can effectively eliminate flocculent carbon by using specific microwave to realize targeted heating, and can eliminate flocculent carbon in lithium iron phosphate products by combining selective oxidation of carbon dioxide, so that the electrochemical performance of the lithium iron phosphate is improved. The method is environment-friendly, can be completed in a relatively short time, improves production efficiency, avoids adverse effects on the structure and performance of the lithium iron phosphate, and does not need to add any additional substances, so that the production cost is low.

Description

Technical Field

[0001] This invention relates to the field of lithium iron phosphate preparation technology, and more specifically, to a method for eliminating flocculent carbon in lithium iron phosphate. Background Technology

[0002] Lithium iron phosphate (LFP) cathode materials are widely used in the new energy vehicle market and energy storage field due to their advantages such as safety, environmental friendliness, low raw material prices, and stable discharge platform. However, their low electronic conductivity and small lithium-ion diffusion coefficient limit their performance in high-power applications, and the LFP batteries prepared with them have a short cycle life and are prone to capacity decay. To improve their performance, a common approach is to use carbon coating to enhance the conductivity, rate performance, and lifespan of LFP cathode materials and LFP batteries. However, during the carbon coating process, uneven local temperature or improper atmosphere control can sometimes lead to the formation of fine flocculent carbon coatings on the material surface. These flocculent carbons can have adverse effects on the material, such as uneven surface roughness, gaps or protrusions between the substrate and the coating layer, thereby affecting the material's conductivity, specific capacity, and other properties.

[0003] Existing technologies primarily reduce the formation of flocculent carbon by altering sintering conditions, such as temperature, time, and atmosphere, or by adding specific additives to change the morphology of flocculent carbon and reduce its impact on material properties. However, these technologies still present some challenges in practical applications. First, changing sintering conditions may affect other properties of lithium iron phosphate, such as capacity and rate performance. Second, adding specific additives may increase production costs and potentially impact the environment. Finally, while eliminating flocculent carbon, existing technologies may also affect the carbon coating on the surface of lithium iron phosphate crystals, adversely affecting the structure and performance of lithium iron phosphate.

[0004] Therefore, effectively eliminating flocculent carbon without affecting other properties of lithium iron phosphate is a significant challenge currently facing the technology. Summary of the Invention

[0005] In view of the above, the present invention provides a method for eliminating flocculent carbon in lithium iron phosphate, which effectively eliminates flocculent carbon in lithium iron phosphate, does not affect other properties of lithium iron phosphate, requires no additional additives, has low production cost, and is environmentally friendly.

[0006] This invention provides a method for eliminating flocculent carbon in lithium iron phosphate, which involves placing the lithium iron phosphate raw material into a microwave heating device, setting the microwave power to 700-900W and the frequency to 2.45GHz, while simultaneously introducing carbon dioxide gas, and then heating for 30-60 minutes, wherein the carbon dioxide gas flow rate is controlled at 1L / min.

[0007] Different substances absorb microwaves differently. This invention utilizes the penetrating and selective heating properties of microwaves to target the flocculent carbon in lithium iron phosphate by using a specific microwave frequency, causing it to react at a relatively low temperature. Simultaneously, carbon dioxide gas is introduced, and its selective oxidation properties are used to oxidize the flocculent carbon to carbon monoxide, thereby effectively eliminating the flocculent carbon. At the same time, while eliminating the flocculent carbon, damage to the carbon coating of lithium iron phosphate is avoided, thus preventing adverse effects on the structure and performance of lithium iron phosphate and improving its electrochemical performance.

[0008] The beneficial effects of this invention are as follows: (1) The present invention uses microwave-assisted elimination of flocculent carbon in lithium iron phosphate. Specific microwaves can achieve targeted heating of flocculent carbon, thus eliminating flocculent carbon more effectively. (2) The present invention combines selective oxidation of carbon dioxide to eliminate flocculent carbon in lithium iron phosphate finished products. This method is not only environmentally friendly, but can also be completed in a relatively short time, thus improving production efficiency. (3) This invention does not change the sintering conditions of lithium iron phosphate, avoids adverse effects on the structure and performance of lithium iron phosphate, and does not add any additional substances, resulting in low production costs. (4) At the same time, the method of the present invention effectively eliminates flocculent carbon and improves the electrochemical performance of lithium iron phosphate; (5) Collect and treat the waste gas generated during microwave-assisted heating and selective carbon dioxide oxidation to reduce the impact on the environment. Attached Figure Description

[0009] Figure 1 This is an SEM image of lithium iron phosphate raw material.

[0010] Figure 2 This is a SEM image of lithium iron phosphate after the sintering temperature was increased to eliminate flocculent carbon.

[0011] Figure 3 This is a SEM image of lithium iron phosphate after flocculent carbon was removed using the method of the present invention in Example 3. Detailed Implementation

[0012] The embodiments of this application will now be described in more detail. This application can be implemented in various forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided to provide a more thorough and complete understanding of the application. It should be understood that the embodiments of this application are for illustrative purposes only and are not intended to limit the scope of protection of this application.

[0013] The process flow of this invention is attached. Figure 1As shown, the embodiments are implemented according to the following technical solutions, specifically: The lithium iron phosphate raw material is placed in a microwave heating device with the microwave power set to 700-900W and the frequency set to 2.45GHz. Simultaneously, carbon dioxide gas is introduced with a flow rate of 1L / min, and then heated for 30-60 minutes.

[0014] Comparative Example 1: Lithium iron phosphate with unremoved flocculent carbon, i.e., the lithium iron phosphate raw material of the present invention.

[0015] Comparative Example 2: Increasing the sintering temperature to eliminate flocculent carbon: The preparation process of lithium iron phosphate raw materials includes batching, mixing, drying and sintering. In this Comparative Example 2, the sintering temperature in the box furnace is increased by 10°C, while other processes remain unchanged.

[0016] Appendix Figure 1 This is a SEM image of lithium iron phosphate raw material, attached. Figure 2 This is a SEM image of lithium iron phosphate after eliminating flocculent carbon by increasing the sintering temperature. (Attached) Figure 3 This is a SEM image of lithium iron phosphate after flocculent carbon removal using the method of the present invention in Example 3. (See attached image.) Figures 1-3 It is evident that lithium iron phosphate raw materials contain a significant amount of flocculent carbon. While increasing the sintering temperature to eliminate flocculent carbon in lithium iron phosphate materials results in a noticeable reduction in flocculent carbon, it is still not thorough enough. However, the lithium iron phosphate materials that have undergone flocculent carbon elimination using the method of this invention show a significant and more thorough reduction in flocculent carbon.

[0017] Table 1: Specific process conditions and performance test results of lithium iron phosphate obtained in the embodiments and comparative examples of the present invention.

[0018] Table 1 shows the specific process conditions and performance test results of lithium iron phosphate in the embodiments and comparative examples of the present invention. As can be seen from Table 1, in Examples 1-6, the electrochemical performance of lithium iron phosphate after eliminating flocculent carbon using the method of the present invention is significantly improved compared to the electrochemical performance of lithium iron phosphate raw material without eliminating flocculent carbon, including charge / discharge performance and conductivity. The lower the resistivity, the better the conductivity. (See attached table.) Figure 1 and attached Figure 2This indicates that the method of the present invention not only effectively eliminates flocculent carbon but also improves the electrochemical performance of lithium iron phosphate. Specifically, as the microwave power increases, the electrochemical performance of the prepared lithium iron phosphate material shows a trend of first increasing and then decreasing, indicating that the microwave power has a significant impact on the performance of lithium iron phosphate. Too low a power results in poor heating of the flocculent carbon, leading to poor reaction with carbon dioxide; too high a power may damage the carbon in the coating layer, causing a decrease in the electrochemical performance of lithium iron phosphate. Furthermore, a short heating time is insufficient to effectively eliminate flocculent carbon, while a long heating time may damage the carbon in the coating layer and increase energy consumption. Therefore, a power of 700–900 W and a heating time of 30–60 min can effectively eliminate flocculent carbon and improve the electrochemical performance of lithium iron phosphate.

[0019] The electrochemical performance of lithium iron phosphate (LFP) with flocculent carbon eliminated by increasing the sintering temperature actually decreased compared to that of LFP raw materials without flocculent carbon elimination. This is because excessively high sintering temperatures can damage the amorphous carbon coating layer, while grain agglomeration and growth increase the Li+ transport path. In addition, excessively high sintering temperatures can easily generate Fe2P impurities, which may block the one-dimensional diffusion channels of Li+, reduce the diffusion coefficient, and thus reduce the electrochemical performance of the material.

[0020] In summary, conventionally prepared lithium iron phosphate raw materials with unremoved flocculent carbon have a large amount of surface flocculent carbon, resulting in poor electrochemical performance. Increasing the sintering temperature to eliminate flocculent carbon is actually detrimental to the electrochemical performance of lithium iron phosphate. However, the method of this invention, through microwave-assisted heating, can specifically heat the flocculent carbon, more effectively allowing the flocculent carbon to react with carbon dioxide, thus eliminating the flocculent carbon more thoroughly without damaging the structure and surface carbon coating of lithium iron phosphate, thereby improving the electrochemical performance of lithium iron phosphate materials.

[0021] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. For example, any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of protection of the claims.

Claims

1. A method for eliminating flocculent carbon in lithium iron phosphate, characterized in that, The process involves placing lithium iron phosphate raw material into a microwave heating device for microwave heating while simultaneously introducing carbon dioxide gas. The microwave power is set to 700–900W, the microwave frequency is set to 2.45GHz, the heating time is 30–60 minutes, and the carbon dioxide gas flow rate is controlled at 1L / min. The method utilizes the penetrating and selective heating properties of microwaves to target the flocculent carbon in lithium iron phosphate by means of microwave frequency, while using the selective oxidation properties of carbon dioxide to oxidize the flocculent carbon into carbon monoxide, thereby eliminating the flocculent carbon while avoiding damage to the carbon coating of lithium iron phosphate.

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