What are the material dispersion issues for LiFePO4 batteries? How to solve?
Due to the low diffusion coefficient of lithium ions and poor conductivity of lithium iron phosphate batteries, the current practice is to make their particles small, or even make them nanoscale, and improve their charge and discharge by shortening the migration path of LI+ and electrons. Speed (theoretically, the migration time is inversely proportional to the square of the migration path). But this brings a series of problems to the processing of lithium batteries.
For example, the most commonly encountered problem is material dispersion.
Pulping is one of the most critical processes in the battery production process. Its core task is to uniformly mix active materials, conductive agents, binders and other materials so that the material properties can be better played. To mix, it must first be able to disperse. As the particles decrease, the corresponding specific surface area increases, the surface energy increases, and the tendency for aggregation between particles increases. The greater the energy required to overcome the surface energy dispersion. At present, mechanical stirring is generally used, and the energy distribution of mechanical stirring is uneven. Only in a certain area, the shear strength is large enough and the energy is high enough to separate the aggregated particles. To improve the dispersing ability, one is to optimize the structure of the stirring equipment to increase the space ratio of the effective dispersion area without changing the maximum shear rate; the other is to increase the stirring power (increase the stirring speed) and increase the shearing speed. The effective dispersion space will also increase. The former belongs to the problem of equipment, how much room for improvement, and coating online does not make comments. In the latter case, the space for improvement is limited, because the shearing speed is raised to a certain limit, which will cause damage to the material and lead to particle breakage.
A more effective method is to use ultrasonic dispersion technology. It's just that the price of ultrasonic equipment is relatively high. The price of the one I contacted some time ago is comparable to that of imported Japanese mechanical mixers. The ultrasonic dispersion process time is short, the overall energy consumption is reduced, the slurry dispersion effect is good, the polymerization of material particles is effectively delayed, and the stability is greatly improved.
In addition, the dispersion effect can be improved by using a dispersant.
