Preparation method of lithium iron phosphate composite conductive paste
Prepare porous graphene through KOH activation of the legal system, and coordinate with carbon nanotubes and carbon black to build a three -dimensional conductive network, solve the problem of selecting and decentralized problems of lithium iron phosphate battery conductive agent, improve the multiplication and low temperature performance of the battery, while reducing the reduction of the battery, while reducing it cost.
Patent Information
- Application Number
- CN202411534466.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-31
- Publication Date
- 2025-01-28
AI Technical Summary
The existing lithium iron phosphate batteries have shortcomings in the selection and dispersion of conductive agents, resulting in high internal resistance, affecting the magnification, low-temperature discharge and cycling performance.
The KOH activation legal preparation of porous graphene is adopted, and through the synergistic effect of carbon nanotubes and carbon black, the three-dimensional conductivity network contacts in the "point-line-surface" is constructed to form excellent ions and electronic conductive networks.
有效降低了Li+离子的传输阻力，提高了电导率，增强了电池的倍率性能和低温放电能力，同时减少了碳纳米管的使用，降低了成本。
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of lithium batteries, and more specifically, to a method for preparing a lithium iron phosphate composite conductive slurry. Background Art
[0002] Lithium iron phosphate batteries are highly safe, low-cost, long-life, and green and sustainable, accounting for more than 90% of the energy storage market. The positive electrode active material, lithium iron phosphate, is a semiconductor with low electronic conductivity and ion diffusion rate. Therefore, lithium iron phosphate batteries are highly dependent on conductive agents during the manufacturing process. If the conductive agent is not selected properly or the proportion is insufficient, the internal resistance will be high, affecting the rate, low-temperature discharge, and cycle performance.
[0003] In the existing technology, although single-walled carbon nanotubes have a large specific surface area and good conductivity, they are difficult to disperse, have limited preparation processes, and are expensive; although graphene has high conductivity and good flexibility, its planar structure hinders the transmission of lithium ions.
[0004] Therefore, the present application provides a method for preparing a lithium iron phosphate composite conductive slurry to solve the problem that graphene conductive additives are not conducive to the diffusion of Li+ ions, and to solve the problems of difficult dispersion, limited preparation process, and high price. Summary of the invention
[0005] The purpose and effect of the present invention are achieved by the following specific technical means: A method for preparing a lithium iron phosphate composite conductive slurry comprises the following steps: Step 1: mixing graphene powder and KOH powder, calcining in an inert gas environment atmosphere to obtain a mixture, washing the obtained mixture with deionized water and then vacuum drying to obtain porous graphene powder; Step 2: dispersing and dissolving a dispersant in a solvent to obtain a solution A, mixing the porous graphene obtained in step 1 with the solution A, and finely grinding them with a sand mill to obtain a slurry B; Step 3: adding carbon nanotubes to the slurry B obtained in step 2, and grinding them homogenously to obtain slurry C; Step 4: Add carbon black to slurry C in step 3 and grind it finely to obtain a uniform composite conductive slurry D.
[0006] Preferably, in step 1, the mass ratio of graphene powder to KOH is 1:10 to 1:2.
[0007] Preferably, in step 1, the calcination temperature is 600° C. to 800° C., and the reaction time is 40 min to 90 min.
[0008] Preferably, in step 2, the dispersant is PVP and the solvent is NMP.
[0009] Preferably, in step three, the carbon nanotubes are a mixture of one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, few-walled carbon nanotubes and thin-walled carbon nanotubes.
[0010] Preferably, in step 4, the solid particle size in the composite conductive paste D is 0.5-5 µm.
[0011] Preferably, in step 4, the weight proportions of the raw materials added to the composite conductive paste D are: graphene 0.1%-2%, carbon nanotubes 0.05%-1.5%, carbon black 0.05%-2%, dispersant 0.1%-1%, and solvent 93.5%-99.7%.
[0012] Beneficial effects of the present invention: (1) The porous graphene prepared by KOH activation method achieves high conductivity and low ion diffusion resistance of graphene, effectively avoiding the Li+ transport problem of flake graphene; (2) Adding carbon nanotubes and carbon black forms a three-dimensional conductive network of "point-line-surface" contact with graphene. Carbon black takes into account the good adsorption of electrolyte and the maintenance of electrolyte properties of the conductive agent. These three conductive agents work synergistically to construct an excellent ionic and electronic conductive network, which can be used to prepare LiFePO4 batteries with high energy density and rate performance.
[0013] (3) The preparation of composite slurry can reduce the use of carbon nanotubes, especially single-walled carbon nanotubes, reduce costs and improve production efficiency. DETAILED DESCRIPTION
[0014] In order to more clearly understand the above-mentioned purpose, features and advantages of the present invention, the present invention is further described in detail in the specific embodiments. The following embodiments are only examples of implementing the present invention. It must be pointed out that the disclosed embodiments do not limit the scope of the present invention. On the contrary, changes and modifications made without departing from the scope of the present invention are all within the scope of patent protection of the present invention. Example 1
[0015] 1g of graphene powder was mixed with 5g of KOH powder, heated at 800°C for 60min under an argon atmosphere, and then the mixture was repeatedly washed with deionized water until neutral and vacuum dried to obtain 1g of porous graphene powder; 1g of PVP dispersant was dispersed and dissolved in 997g of NMP solvent to obtain solution A; then the porous graphene was mixed with solution A and finely ground with a sand mill to obtain slurry B; then 0.5g of single-walled carbon nanotubes was added to slurry B and ground homogeneously to obtain slurry C; finally, 0.5g of carbon black was added to slurry C and finely ground in a sand mill to obtain a uniform composite conductive slurry D with a slurry particle size of 3 µm. Example 2
[0016] 1g of graphene powder was mixed with 5g of KOH powder, heated at 800°C for 60min under an argon atmosphere, and then the mixture was repeatedly washed with deionized water until neutral, and vacuum dried to obtain 1g of porous graphene powder; 1g of PVP dispersant was dispersed and dissolved in 997g of NMP solvent to obtain solution A; then the porous graphene was mixed with solution A and finely ground with a sand mill to obtain slurry B; then 0.5g of multi-walled carbon nanotubes was added to slurry B and ground homogeneously to obtain slurry C; finally, 0.5g of carbon black was added to slurry C and finely ground in a sand mill to obtain a uniform composite conductive slurry D with a slurry particle size of 3.5 µm. Example 3
[0017] 1 g of graphene powder was mixed with 5 g of KOH powder, heated at 800 ° C for 60 min under argon atmosphere, and then the mixture was repeatedly washed with deionized water until neutral and vacuum dried to obtain 1 g of porous graphene powder; 1 g of PVP dispersant was dispersed and dissolved in 996 g of NMP solvent to obtain solution A; then the porous graphene was mixed with solution A and finely ground with a sand mill to obtain slurry B; then 0.5 g of single-walled carbon nanotubes was added to slurry B and ground homogeneously to obtain slurry C; finally, 1.5 g of carbon black was added to slurry C and finely ground in a sand mill to obtain a uniform composite conductive slurry D with a slurry particle size of 2.5 µm.
[0018] Comparative Example 1 1 g of PVP dispersant was dispersed and dissolved in 997 g of NMP solvent to obtain solution A; then 1 g of graphene powder that had not been activated by KOH was mixed with solution A and finely ground with a sand mill to obtain slurry B; then 0.5 g of single-walled carbon nanotubes was added to slurry B and ground homogeneously to obtain slurry C; finally, 0.5 g of carbon black was added to slurry C and finely ground in a sand mill to obtain a uniform composite conductive slurry D with a slurry particle size of 2 µm.
[0019] Comparative Example 2 1g of graphene powder was mixed with 5g of KOH powder, heated at 800°C for 60min under an argon atmosphere, and then the mixture was repeatedly washed with deionized water until neutral, and vacuum dried to obtain 1g of porous graphene powder; 1g of PVP dispersant was dispersed and dissolved in 997g of NMP solvent to obtain solution A; then the porous graphene was mixed with solution A and finely ground with a sand mill to obtain slurry B; then 1g of single-walled carbon nanotubes was added to slurry B and ground homogeneously to obtain composite conductive slurry C, whose slurry particle size was 4 µm.
[0020] Comparative Example 3 1 g of PVP dispersant was dispersed and dissolved in 997 g of NMP solvent to obtain solution A; then 0.5 g of single-walled carbon nanotubes was mixed with solution A and ground homogeneously with a sand mill to obtain slurry B; finally, 1.5 g of carbon black was added to slurry B and finely ground in a sand mill to obtain a uniform composite conductive slurry C with a slurry particle size of 2.5 µm.
[0021] The composite conductive paste obtained in the embodiment and the comparative example was used for lithium iron phosphate battery, and the same amount of active material, binder and composite conductive paste was used to prepare the positive electrode sheet, and the weight percentage of lithium iron phosphate, composite conductive paste and binder was 96.5%:1.5%:2.5%. The button half-cell was assembled and the charge and discharge capacity retention rate test was carried out on the machine. The test results are shown in Table 1.
[0022] Table 1 Experimental protocol Powder resistance (mΩ) Capacity retention rate after 50 cycles at 0.5C (%) Example 1 20.5 99.5 Example 2 21.7 97.3 Example 3 23.2 99.1 Comparative Example 1 21.1 93.2 Comparative Example 2 15.6 85.6 Comparative Example 3 30.3 91.3 After testing, 1g of graphene powder was mixed with 5g of KOH powder, heated at 800℃ for 60min under argon atmosphere, and then the mixture was repeatedly washed with deionized water until neutral, and vacuum dried to obtain 1g of porous graphene powder; 1g of PVP dispersant was dispersed and dissolved in 997g of NMP solvent to obtain solution A; then the porous graphene was mixed with solution A and finely ground with a sand mill to obtain slurry B; then 0.5g of multi-walled carbon nanotubes was added to slurry B and ground homogeneously to obtain slurry C; finally, 0.5g of carbon black was added to slurry C and finely ground in a sand mill to obtain a uniform composite conductive slurry D with a slurry particle size of 3.5µm. The composite conductive slurry obtained by this method has the best use effect.
Claims
1. A method for preparing a lithium iron phosphate composite conductive slurry, characterized in that: The following steps are involved: Step 1: mixing graphene powder and KOH powder, calcining in an inert gas environment atmosphere to obtain a mixture, washing the obtained mixture with deionized water and then vacuum drying to obtain porous graphene powder; Step 2: dispersing and dissolving a dispersant in a solvent to obtain a solution A, mixing the porous graphene obtained in step 1 with the solution A, and finely grinding them with a sand mill to obtain a slurry B; Step 3: adding carbon nanotubes to the slurry B obtained in step 2, and grinding them homogenously to obtain slurry C; Step 4: Add carbon black to slurry C in step 3 and grind it finely to obtain a uniform composite conductive slurry D.
2. The method for preparing a lithium iron phosphate composite conductive slurry according to claim 1, characterized in that: In the step 1, the mass ratio of graphene powder to KOH is 1:10-1:
2.
3. The method for preparing a lithium iron phosphate composite conductive slurry according to claim 1, characterized in that: In the step 1, the calcination temperature is 600° C. to 800° C., and the reaction time is 40 min to 90 min.
4. The method for preparing a lithium iron phosphate composite conductive slurry according to claim 1, characterized in that: In the step 2, the dispersant is PVP and the solvent is NMP.
5. The method for preparing a lithium iron phosphate composite conductive slurry according to claim 1, characterized in that: In the step three, the carbon nanotubes are a mixture of one or more of single-walled carbon nanotubes, multi-walled carbon nanotubes, few-walled carbon nanotubes and thin-walled carbon nanotubes.
6. The method for preparing a lithium iron phosphate composite conductive slurry according to claim 1, characterized in that: In the step 4, the solid particle size in the composite conductive paste D is 0.5-5 µm.
7. The method for preparing a lithium iron phosphate composite conductive slurry according to claim 1, characterized in that: In the step 4, the weight proportions of the raw materials added to the composite conductive paste D are: graphene 0.1%-2%, carbon nanotubes 0.05%-1.5%, carbon black 0.05%-2%, dispersant 0.1%-1%, and solvent 93.5%-99.7%.