Briefly describe the structural characteristics of the high Lithium -ion battery diaphragm

　　1) Thickness. The thickness of the high Lithium -ion battery diaphragm is generally ≤25 μm. Under the premise of ensuring a certain mechanical strength, the thinner the thickness of the diaphragm, the better. At present, most of the new high -energy batteries use single -layer diaphragm with a membrane thickness of 20 μm or 16 μm; the diaphragm of the battery used in electric vehicles (EV) and hybrid electric vehicles (HEV) is about 40 μm. And the thicker the diaphragm, the better its mechanical strength, and it is not easy to be short -circuited during the assembly battery process.

　　2) Porph and distribution. As a battery diaphragm material, it has a micropore structure that allows absorbing electrolytes; in order to ensure the nature of the electrode/electrolyte interface in the battery, the distribution of micro -holes in the entire diaphragm material should be uniform. The size of the pore diameter and distribution have a direct impact on the performance of the battery: the pore diameter is too large, and it is easy to make the positive and negative electrode direct contact or easily pierced by high Lithium branches to cause short circuit; too small the aperture can increase the resistor. The distribution of micro -holes is uneven, and the local current will be excessive during work, which will affect the performance of the battery.

　　3) Pole rate. It can be used to characterize the amount of diaphragm gas under one time and pressure, which is important to reflect the smoothness of high Lithium ions through the diaphragm. The pore rate is very important for the permeability of the membrane and the capacity of the electrolyte. The pore rate of most commercial lithium-ion battery diaphragms is between 40 % -50 %.

　　Power battery manufacturers believe that after soaking the weighed microre film (WD) for 2H in the artenol 2h, use the filter paper to gently dry the liquid on the surface, and then the weighing (ww) to get the micro -micro -micro -micro The quality of the pore membrane absorbs the quality wb = ww-wd. In the formula, the weight of the WD microre film (g); the weight (g) after soaking the ww; the mass (G) of the WB positive butanol; the density of ρB positive butanol (G/CM3); VP dry membrane volume (CM3).

　　4) Through sex. Under certain conditions (pressure, measurement area), a certain amount of air required by the diaphragm is called the Gurly value. The size of the diaphragm passability is the result of the comprehensive factors of the internal pores such as the septum porosity, the shape of the pore, the shape of the pore, the shape of the pore and the pore tortuousness.

　　5) Surface shape structure of SEM diaphragm.

　　6) Base weight of the diaphragm. 1) Take three septum samples of 30cm in length. 2) Put these three samples and fold them together. 3) Weighing and recorded the quality of the sample (milligrams).

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