Li-ion battery slurry is formed by the dispersion of solid particles such as electroactive substances and conductive agents in the binder solution. The active substance, the conductive agent and other solid components should be evenly dispersed in the solvent in the form of tiny particles when coating Of the coating can not be seen as granular objects.Industry commonly used fineness of this indicator to detect the degree of dispersion of the particulate material in the slurry.Fineness is an important performance indicators of the battery slurry, which the formation of the coating surface quality , Uniformity and storage stability of the slurry have a great influence on the fine particles, a good degree of dispersion of the slurry, the solid particles can be well wetted, the coating prepared uniform, smooth surface, does not appear vertical Straight scratches, but also during the storage of particles is not easy precipitation, caking and other phenomena, storage stability is good.If there are large aggregates particles in the slurry, on the one hand shows the uneven distribution of additives such as conductive agent, the prepared Coating uniformity is poor, inevitable battery consistency is poor.In addition, in the coating process, the large particles gathered in the coating knife roll slit or extrusion coating die discharge slit, the prepared coating will appear vertical Scratches Depression.
Scratch fineness gauges are currently used to measure the fineness of a scraper. A scraper fineness gauge is a polished plate with wedge-shaped grooves ranging from zero to a few microns deep with graduations on the sides of the grooves to indicate the depth of the grooves. The sample is dropped into the deepest part of the trench during the measurement. A flat, two-edged blade is then used to make vertical contact with the plate and the paint is pulled over the entire length of the slot at a suitable speed and then observed in the direction of the incident light at a 30 ° angle The depth of uniform exposure of the particles in the groove, in this thickness indicates the fineness of the sample.
Reference to national standards "GB / T 6753.1-2007 paint, varnish and printing ink grinding fineness determination", this article briefly introduces the basic knowledge of fineness measurement.
1, fineness meter introduction
Gauge generally consists of fineness board and scraper.Lightness board is generally made of stainless steel, the upper surface of the steel should be fine grinding or grinding process, the surface should be smooth, open on the surface of one or two parallel long sides Chutes, which are evenly descending along the long sides, have a given depth (for example 100 μm) at one end and zero at the other and are to be subdivided according to the specifications in Table 1. The scraper is made of single-edged or double-edged steel, Long edge scraper blades are straight and arcuate, and the scraper blade needs to be periodically inspected for wear, damage or deformation. If it is found to be damaged, the scraper blade can not be used. Place the scraper blade in a soft material container when not in use. Meter as shown in Figure 1. Lithium-ion battery slurry generally used scraper gauges of 100μm range.
Figure 1 scraper fineness meter
2, measuring steps
(1) Place a thoroughly cleaned, dry scraper on a flat, horizontal, non-slip surface;
(2) Drop enough sample into the deepest part of the groove, ie, the largest part of the scale value, and make the sample slightly overflow;
(3) Hold the scraper with both thumbs and index fingers. Place the doctor blade horizontally on the largest scale (at the sample edge) of the scraper so that the long side of the scraper is parallel to the broad side of the scraper and perpendicular to the scraper surface Contact within 1 to 2 seconds, the scraper from the largest scale parts to the smallest part of the scratch scratch;
(4) Immediately after scraping the sample (no more than 5 seconds), make the line of sight be at an angle of 20 ° ~ 30 ° with the plane of the groove. The particles in the light observation groove should be uniformly exposed, and note the corresponding scale value.
3, the test results reading
Observe that the sample first appears densely packed, especially if it contains 5-10 particles in a 3mm strip (as shown in Figures 2 and 3). The scattered points above the dense spots are not considered, And then determine the next strip of the upper limit of the scale, that is, the fineness of the test sample for different range of fineness meter, the reading accuracy were:
(1) Range 100μm fineness plate, reading accuracy of 5μm
(2) Range of 50μm fineness of the plate, the reading accuracy of 2μm
(3) 25μm measuring range of fineness, reading accuracy of 1μm
Calculate the average of three measurements and record the test results with the appropriate range of accuracy.
Figure 2 fineness meter reading example 1
Figure 3 Fine meter reading example 2
