Preparation method of composite lithium supplementing agent

Abstract

The CNTs-Mn / lithium-rich lithium iron ferrite composite lithium supplement prepared by this invention can effectively improve battery performance. With the increase of CNTs-Mn content in the composite lithium supplement, the battery capacity retention rate continuously improves; however, the lithium-ion diffusion coefficient shows a trend of first increasing and then decreasing. Therefore, the CNTs-Mn content in the CNTs-Mn / lithium-rich lithium iron ferrite composite lithium supplement needs to be controlled between 8.7wt% and 23.6wt%.

Description

Technical Field

[0001] This invention relates to the field of lithium supplements, and more specifically to a method for preparing a composite lithium supplement. Background Technology

[0002] In the current battery field, lithium replenishment agents are crucial for improving battery performance. However, existing single-type lithium replenishment agents have significant limitations. For example, some lithium metal-based replenishment agents, while theoretically having high lithium content, are chemically reactive, exhibit poor stability in battery systems, and are prone to safety issues. While some inorganic lithium salt replenishment agents have better stability, they perform poorly in terms of lithium replenishment efficiency, failing to meet the lithium demands during rapid charge and discharge processes. Some organic lithium replenishment agents, although they can improve battery cycle performance to some extent, are expensive and difficult to apply on a large scale.

[0003] Therefore, a single type of lithium replenisher cannot simultaneously meet the requirements of stability, lithium replenishment efficiency, and cost. To overcome these limitations, the development of composite lithium replenishers has become an inevitable trend. By combining the advantages of different types of lithium replenishers, it is hoped that lithium replenisher products with superior performance and outstanding overall characteristics can be developed to meet the growing demand for high-performance batteries. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a composite lithium replenishing agent, which can improve the capacity retention rate and lithium-ion diffusion coefficient of the battery.

[0005] The technical solution of the present invention is as follows: A method for preparing a composite lithium supplement includes: Preparation of CNTs-Mn: Take 5-8g of multi-walled carbon nanotubes and 7.5-9g of polyoxyethylene polyoxypropylene ether dispersant, add them to deionized water, and stir with a magnetic stirrer at a speed of 300-400r / min for 12-15 hours to form a uniform colloid. Add 1-1.2g of manganese salt to the colloid and continue stirring for 9-12 hours. After ultrasonic treatment at a power of 400-450W for 3-5 hours, vacuum filter the filtrate and vacuum dry it for 22-24 hours. Then place it in a tube furnace and heat it to 350-360℃ at a heating rate of 3-3.5℃ / min. Pass a mixed gas of Ar and H2 through the furnace and carry out a high-temperature thermal reduction reaction for 4-6 hours to obtain CNTs-Mn. Preparation of lithium-rich lithium iron oxide: Accurately weigh lithium oxide and iron oxide according to the Li:Fe molar ratio of 5:1, put them into a high-temperature resistant crucible, raise the furnace temperature to 850-880℃ in an inert environment at a heating rate of 5-6℃ / min, calcine for 18-20 hours, and then let the furnace cool naturally to room temperature after the calcination is completed. Mixing of the composite lithium supplement: Weigh CNTs-Mn and lithium iron ferrite, making CNTs-Mn account for 8.7-23.6 wt% of the total mass of the mixture. Add both to a planetary ball mill, and add anhydrous ethanol as a dispersant. Ball mill at 600-650 r / min for 2.5-3 hours. Transfer the ball-milled material to a vacuum drying oven and dry at 80-85℃ for 18-20 hours to remove the ethanol. After drying, take out the material and grind it again at 500-600 r / min for 1.5-2 hours to obtain the CNTs-Mn / lithium iron ferrite composite lithium supplement.

[0006] Preferably, the manganese salt is 1g.

[0007] Preferably, the multi-walled carbon nanotubes weigh 5g.

[0008] Preferably, the polyoxyethylene polyoxypropylene ether is 7.5g.

[0009] Preferably, CNTs-Mn account for 15.3 wt% of the total mass of the mixture.

[0010] The CNTs-Mn / lithium-rich lithium iron ferrite composite lithium supplement prepared by this invention can effectively improve battery performance. With the increase of CNTs-Mn content in the composite lithium supplement, the battery capacity retention rate continuously improves; however, the lithium-ion diffusion coefficient shows a trend of first increasing and then decreasing. Therefore, the CNTs-Mn content in the CNTs-Mn / lithium-rich lithium iron ferrite composite lithium supplement needs to be controlled between 8.7wt% and 23.6wt%. Detailed Implementation

[0011] The technical effects of the present invention will be verified through specific embodiments below, but the implementation of the present invention is not limited thereto.

[0012] Example 1 Preparation of CNTs-Mn: 5g of multi-walled carbon nanotubes and 7.5g of polyoxyethylene polyoxypropylene ether dispersant were added to 300mL of deionized water. The mixture was stirred at 300r / min for 12 hours using a magnetic stirrer to form a homogeneous colloid. 1g of manganese salt was added to the colloid, and stirring continued for 9 hours. After ultrasonic treatment at 400W for 3 hours, the mixture was vacuum filtered. The filtrate was then vacuum dried for 22 hours and placed in a tube furnace. The furnace was heated to 350℃ at a heating rate of 3℃ / min, and a mixture of Ar and H2 gas was introduced. The mixture underwent a high-temperature thermal reduction reaction for 4 hours to obtain CNTs-Mn. Preparation of lithium-rich lithium iron ore oxide: Accurately weigh lithium oxide and iron oxide according to a Li:Fe molar ratio of 5:1. Place them in a high-temperature resistant crucible and calcine at a rate of 5℃ / min in an inert environment until the furnace temperature reaches 880℃, then calcine for 18 hours. After calcination, allow the furnace to cool naturally to room temperature. The entire process is strictly isolated from air and moisture to prevent hydrolysis of the raw materials and deterioration of the product. Mixing of the composite lithium supplement: Weigh CNTs-Mn and lithium-rich lithium iron ferrite, ensuring that CNTs-Mn accounts for 8.7 wt% of the total mass of the mixture. Add both to a planetary ball mill, along with 60 mL of anhydrous ethanol as a dispersant. Ball mill at 600 rpm for 2.5 hours. Transfer the milled material to a vacuum drying oven and dry at 85°C for 18 hours to remove the ethanol. After drying, remove the material and grind it again at 500 rpm for 1.5 hours to obtain the composite lithium supplement.

[0013] Example 2 Preparation of CNTs-Mn: 5g of multi-walled carbon nanotubes and 7.5g of polyoxyethylene polyoxypropylene ether dispersant were added to 300mL of deionized water. The mixture was stirred at 300r / min for 12 hours using a magnetic stirrer to form a homogeneous colloid. 1g of manganese salt was added to the colloid, and stirring continued for 9 hours. After ultrasonic treatment at 400W for 3 hours, the mixture was vacuum filtered. The filtrate was vacuum dried for 22 hours, then placed in a tube furnace and heated to 350℃ at a heating rate of 3℃ / min. A mixture of Ar and H2 gas was introduced, and the mixture underwent a high-temperature thermal reduction reaction for 4 hours to obtain CNTs-Mn. Preparation of lithium-rich lithium iron ore oxide: Accurately weigh lithium oxide and iron oxide according to a Li:Fe molar ratio of 5:1. Place them in a high-temperature resistant crucible and calcine at a rate of 5℃ / min in an inert environment until the furnace temperature reaches 880℃, then calcine for 18 hours. After calcination, allow the furnace to cool naturally to room temperature. The entire process is strictly isolated from air and moisture to prevent hydrolysis of the raw materials and deterioration of the product. Mixing of the composite lithium supplement: Weigh CNTs-Mn and lithium-rich lithium iron ferrite, ensuring CNTs-Mn accounts for 12.5 wt% of the total mixture. Add both to a planetary ball mill, along with 60 mL of anhydrous ethanol as a dispersant. Ball mill at 600 rpm for 2.5 hours. Transfer the milled material to a vacuum drying oven and dry at 85°C for 18 hours to remove the ethanol. After drying, remove the material and grind it again at 500 rpm for 1.5 hours to obtain the composite lithium supplement.

[0014] Example 3 Preparation of CNTs-Mn: 5g of multi-walled carbon nanotubes and 7.5g of polyoxyethylene polyoxypropylene ether dispersant were added to 300mL of deionized water. The mixture was stirred at 300r / min for 12 hours using a magnetic stirrer to form a homogeneous colloid. 1g of manganese salt was added to the colloid, and stirring continued for 9 hours. After ultrasonic treatment at 400W for 3 hours, the mixture was vacuum filtered. The filtrate was vacuum dried for 22 hours, then placed in a tube furnace and heated to 350℃ at a heating rate of 3℃ / min. A mixture of Ar and H2 gas was introduced, and the mixture underwent a high-temperature thermal reduction reaction for 4 hours to obtain CNTs-Mn. Preparation of lithium-rich lithium iron ore oxide: Accurately weigh lithium oxide and iron oxide according to a Li:Fe molar ratio of 5:1. Place them in a high-temperature resistant crucible and calcine at a rate of 5℃ / min in an inert environment until the furnace temperature reaches 880℃, then calcine for 18 hours. After calcination, allow the furnace to cool naturally to room temperature. The entire process is strictly isolated from air and moisture to prevent hydrolysis of the raw materials and deterioration of the product. Mixing of the composite lithium supplement: Weigh CNTs-Mn and lithium iron ferrite, ensuring CNTs-Mn accounts for 15.3 wt% of the total mixture. Add both to a planetary ball mill, along with 60 mL of anhydrous ethanol as a dispersant. Ball mill at 600 rpm for 2.5 hours. Transfer the milled material to a vacuum drying oven and dry at 85°C for 18 hours to remove the ethanol. After drying, remove the material and grind it again at 500 rpm for 1.5 hours to obtain the composite lithium supplement.

[0015] Example 4 Preparation of CNTs-Mn: 5g of multi-walled carbon nanotubes and 7.5g of polyoxyethylene polyoxypropylene ether dispersant were added to 300mL of deionized water. The mixture was stirred at 300r / min for 12 hours using a magnetic stirrer to form a homogeneous colloid. 1g of manganese salt was added to the colloid, and stirring continued for 9 hours. After ultrasonic treatment at 400W for 3 hours, the mixture was vacuum filtered. The filtrate was vacuum dried for 22 hours, then placed in a tube furnace and heated to 350℃ at a heating rate of 3℃ / min. A mixture of Ar and H2 gas was introduced, and the mixture underwent a high-temperature thermal reduction reaction for 4 hours to obtain CNTs-Mn. Preparation of lithium-rich lithium iron ore oxide: Accurately weigh lithium oxide and iron oxide according to a Li:Fe molar ratio of 5:1. Place them in a high-temperature resistant crucible and calcine at a rate of 5℃ / min in an inert environment until the furnace temperature reaches 880℃, then calcine for 18 hours. After calcination, allow the furnace to cool naturally to room temperature. The entire process is strictly isolated from air and moisture to prevent hydrolysis of the raw materials and deterioration of the product. Mixing of the composite lithium supplement: Weigh CNTs-Mn and lithium-rich lithium iron ferrite, ensuring CNTs-Mn accounts for 19.1 wt% of the total mixture. Add both to a planetary ball mill, along with 60 mL of anhydrous ethanol as a dispersant. Ball mill at 600 rpm for 2.5 hours. Transfer the milled material to a vacuum drying oven and dry at 85°C for 18 hours to remove the ethanol. After drying, remove the material and grind it again at 500 rpm for 1.5 hours to obtain the composite lithium supplement.

[0016] Example 5 Preparation of CNTs-Mn: 5g of multi-walled carbon nanotubes and 7.5g of polyoxyethylene polyoxypropylene ether dispersant were added to 300mL of deionized water. The mixture was stirred at 300r / min for 12 hours using a magnetic stirrer to form a homogeneous colloid. 1g of manganese salt was added to the colloid, and stirring continued for 9 hours. After ultrasonic treatment at 400W for 3 hours, the mixture was vacuum filtered. The filtrate was vacuum dried for 22 hours, then placed in a tube furnace and heated to 350℃ at a heating rate of 3℃ / min. A mixture of Ar and H2 gas was introduced, and the mixture underwent a high-temperature thermal reduction reaction for 4 hours to obtain CNTs-Mn. Preparation of lithium-rich lithium iron ore oxide: Accurately weigh lithium oxide and iron oxide according to a Li:Fe molar ratio of 5:1. Place them in a high-temperature resistant crucible and calcine at a rate of 5℃ / min in an inert environment until the furnace temperature reaches 880℃, then calcine for 18 hours. After calcination, allow the furnace to cool naturally to room temperature. The entire process is strictly isolated from air and moisture to prevent hydrolysis of the raw materials and deterioration of the product. Mixing of the composite lithium supplement: Weigh CNTs-Mn and lithium-rich lithium iron ferrite, ensuring CNTs-Mn accounts for 23.6 wt% of the total mixture. Add both to a planetary ball mill, along with 60 mL of anhydrous ethanol as a dispersant. Ball mill at 600 rpm for 2.5 hours. Transfer the milled material to a vacuum drying oven and dry at 85°C for 18 hours to remove the ethanol. After drying, remove the material and grind it again at 500 rpm for 1.5 hours to obtain the composite lithium supplement.

[0017] Comparative Example 1 Preparation of CNTs-Mn: 5g of multi-walled carbon nanotubes and 7.5g of polyoxyethylene polyoxypropylene ether dispersant were added to 300mL of deionized water. The mixture was stirred at 300r / min for 12 hours using a magnetic stirrer to form a homogeneous colloid. 1g of manganese salt was added to the colloid, and stirring continued for 9 hours. After ultrasonic treatment at 400W for 3 hours, the mixture was vacuum filtered. The filtrate was vacuum dried for 22 hours, then placed in a tube furnace and heated to 350℃ at a heating rate of 3℃ / min. A mixture of Ar and H2 gas was introduced, and the mixture underwent a high-temperature thermal reduction reaction for 4 hours to obtain CNTs-Mn. Preparation of lithium-rich lithium iron ore oxide: Accurately weigh lithium oxide and iron oxide according to a Li:Fe molar ratio of 5:1. Place them in a high-temperature resistant crucible and calcine at a rate of 5℃ / min in an inert environment until the furnace temperature reaches 880℃, then calcine for 18 hours. After calcination, allow the furnace to cool naturally to room temperature. The entire process is strictly isolated from air and moisture to prevent hydrolysis of the raw materials and deterioration of the product. Mixing of the composite lithium supplement: Weigh CNTs-Mn and lithium iron ferrite, ensuring CNTs-Mn accounts for 2.5 wt% of the total mixture. Add both to a planetary ball mill, along with 60 mL of anhydrous ethanol as a dispersant. Ball mill at 600 rpm for 2.5 hours. Transfer the milled material to a vacuum drying oven and dry at 85°C for 18 hours to remove the ethanol. After drying, remove the material and grind it again at 500 rpm for 1.5 hours to obtain the composite lithium supplement.

[0018] Comparative Example 2 Preparation of CNTs-Mn: 5g of multi-walled carbon nanotubes and 7.5g of polyoxyethylene polyoxypropylene ether dispersant were added to 300mL of deionized water. The mixture was stirred at 300r / min for 12 hours using a magnetic stirrer to form a homogeneous colloid. 1g of manganese salt was added to the colloid, and stirring continued for 9 hours. After ultrasonic treatment at 400W for 3 hours, the mixture was vacuum filtered. The filtrate was vacuum dried for 22 hours, then placed in a tube furnace and heated to 350℃ at a heating rate of 3℃ / min. A mixture of Ar and H2 gas was introduced, and the mixture underwent a high-temperature thermal reduction reaction for 4 hours to obtain CNTs-Mn. Preparation of lithium-rich lithium iron ore oxide: Accurately weigh lithium oxide and iron oxide according to a Li:Fe molar ratio of 5:1. Place them in a high-temperature resistant crucible and calcine at a rate of 5℃ / min in an inert environment until the furnace temperature reaches 880℃, then calcine for 18 hours. After calcination, allow the furnace to cool naturally to room temperature. The entire process is strictly isolated from air and moisture to prevent hydrolysis of the raw materials and deterioration of the product. Mixing of the composite lithium supplement: Weigh CNTs-Mn and lithium iron ferrite, ensuring CNTs-Mn accounts for 40 wt% of the total mass of the mixture. Add both to a planetary ball mill, along with 60 mL of anhydrous ethanol as a dispersant. Ball mill at 600 rpm for 2.5 hours. Transfer the milled material to a vacuum drying oven and dry at 85°C for 18 hours to remove the ethanol. After drying, remove the material and grind it again at 500 rpm for 1.5 hours to obtain the composite lithium supplement.

[0019] The performance of the composite lithium replenishing agents in Examples 1-5 and Comparative Examples 1-2 is characterized below. The testing process involved assembling button cells, with SiO₂ as the negative electrode. X The cathode is an NCM ternary cathode. To ensure the comparability of each group of experiments, all process parameters of each group of samples were identical except for the lithium replenishment agent. Meanwhile, a sample without added lithium replenishment agent was used as a blank control group. The experimental results are shown in Table 1, where the capacity retention rate represents the capacity retention rate of the battery after 200 charge-discharge cycles at 1C.

[0020] Table 1 Test data for each sample As shown in Table 1, the CNTs-Mn / lithium-rich lithium iron phosphate composite lithium supplement prepared in this invention can effectively improve battery performance. With the increase of CNTs-Mn content in the composite lithium supplement, the battery capacity retention rate continuously improves; however, the lithium-ion diffusion coefficient shows a trend of first increasing and then decreasing. Therefore, the CNTs-Mn content in the CNTs-Mn / lithium-rich lithium iron phosphate composite lithium supplement needs to be controlled between 8.7wt% and 23.6wt%.

[0021] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a composite lithium supplement, characterized by, The preparation method includes: Preparation of CNTs-Mn: Take 5-8g of multi-walled carbon nanotubes and 7.5-9g of polyoxyethylene polyoxypropylene ether dispersant, add them to deionized water, and stir with a magnetic stirrer at a speed of 300-400r / min for 12-15 hours to form a uniform colloid. Add 1-1.2g of manganese salt to the colloid and continue stirring for 9-12 hours. After ultrasonic treatment at a power of 400-450W for 3-5 hours, vacuum filter the filtrate and vacuum dry it for 22-24 hours. Then place it in a tube furnace and heat it to 350-360℃ at a heating rate of 3-3.5℃ / min. Pass a mixed gas of Ar and H2 through the furnace and carry out a high-temperature thermal reduction reaction for 4-6 hours to obtain CNTs-Mn. Preparation of lithium-rich lithium iron oxide: Accurately weigh lithium oxide and iron oxide according to the Li:Fe molar ratio of 5:1, put them into a high-temperature resistant crucible, raise the furnace temperature to 850-880℃ in an inert environment at a heating rate of 5-6℃ / min, calcine for 18-20 hours, and then let the furnace cool naturally to room temperature after the calcination is completed. Mixing of the composite lithium supplement: Weigh CNTs-Mn and lithium iron ferrite, making CNTs-Mn account for 8.7-23.6 wt% of the total mass of the mixture. Add both to a planetary ball mill, and add anhydrous ethanol as a dispersant. Ball mill at 600-650 r / min for 2.5-3 hours. Transfer the ball-milled material to a vacuum drying oven and dry at 80-85℃ for 18-20 hours to remove the ethanol. After drying, take out the material and grind it again at 500-600 r / min for 1.5-2 hours to obtain the CNTs-Mn / lithium iron ferrite composite lithium supplement.

2. A process according to claim 1, wherein the process is carried out at a temperature of from 20 to 100°C. The manganese salt is 1g.

3. A process according to claim 1 or 2, characterised in that, The multi-walled carbon nanotubes weigh 5g.

4. A preparation method as described in claim 1, characterized in that, The polyoxyethylene polyoxypropylene ether is 7.5g.

5. A preparation method as described in claim 1, characterized in that, CNTs-Mn accounted for 15.3 wt% of the total mass of the mixture.

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