Introduction of compaction density of four positive materials

It is well known that compaction density is generally affected by true density and material morphology.

Real density.

The compaction density of the material is mainly affected by the true density. The true density of different materials is: lithium cobalt acid: 5.1, lithium manganese acid: 4.2, lithium iron phosphate: 3.6, and the triple material is composed of different, true density. Change, general type 111, Take BC-618 of the United States 3M as an example, which is about 4.8, so it is arranged in order of true density from large to small. The order of the four materials is as follows: lithium cobalt acid & GT; Three yuan & GT; Lithium manganate & GT; Lithium iron phosphate, which is also in line with the current trend of compaction density, shows that true density is the biggest factor affecting compaction of a material.

Morphology structure

The surface smoothness of the material, the size of the internal voids of the secondary particles, and the degree of compaction of the material are all factors that affect the compaction density of the material. The current lithium cobalt acid is a primary particle, which does not have the effect of the internal clearance of the secondary particle., Lithium manganate and ternary materials of our company have also been made into primary particles of lithium-like cobalt acid(lithium manganate can be a single crystal, there is controversy over ternary materials), and the compaction density has also been increased to lithium manganate(2.9-3.2), respectively. (a) ternary(3.7-3 .9), with respect to lithium iron phosphate(which is special and will be explained in the part of the ratio performance), which limits the further increase in compaction of the material due to its nanotechnology, and the particle size distribution is a more complex factor, Reasonable particle size distribution can be appropriately increased compaction, which can generally be adjusted according to their own products.

Multiplication performance

The ratio performance is an electrochemical property that has nothing to do with the objective compaction density of the material, but it is necessary to elaborate on the application of the battery. Lithium manganate & GT; Lithium cobalt acid & GT; ternary material & GT; Lithium iron phosphate. In order to ensure the doubling performance of the material, the currently industrialized products have been adjusted in the process to ensure their doubling performance. Therefore, the current D50's general range is also proportional to the ploidability and the greater the ploidability. product, Generally, the larger the particle size, because the large particle size can ensure that the compaction density of the material is higher(although the ratio between the two is not strictly corresponding), of course, the pursuit of high magnification products in special areas is an exception.

Therefore, we can reasonably believe that the ratio performance has limited the increase of compaction density to a certain extent.

The above is a description of the compaction density. For some customers 'questions about the compaction and doubling performance of the current particle product, the following special explanations are made:

(Supplement: Our way to increase compaction is to make the product a primary particle of lithium cobalt like acid)

There is no doubt that the compaction density of single crystal primary particles is higher than that of secondary particles, but the new problem brought about is that it may affect the ratio performance because the ratio performance is highly correlated with the transmission rate of lithium ions within the particles. The smaller the particle size, The faster the transmission rate(which is also the main reason why lithium iron phosphate must be nanocrystallized), the small particles of ordinary secondary particles are nanowires or below 1 micron, so even if the particle size D50 of the secondary particles is greater than ten or even tens of microns, The rate performance is still good. But another advantage of a single crystal particle is that the free-grown crystal surface is very smooth and in close contact with the conductive agent. In addition, there are few defects in the inner lattice of the free-grown crystal at high temperatures, making the transmission of Li ions more smooth. In addition, We make the particle size smaller(less than the secondary agglomeration particles) also contributes to the improvement of the ploidy performance. As for the specific performance of many customers have done specific tests, do not do too much description.

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