What is the effect of the SEI film on the battery performance?


The use of THE SEI should be analyzed from its own characteristics: THE SEI is an interface layer between the electrode material and electrolyte, which separates the two.Has the characteristics of solid electrolyte.Li+ can pass, but electrons can't.

1. The degree of corrosion caused by the reaction between lithium metal and electrolyte components is determined by the passivation performance of the SEI film on its surface.

2. In the dissolution-deposition process of lithium, it must occur through THE SEI film, and the migration of lithium ions through the SEI film is the rate control step of the lithium deposition-dissolution process, which determines the uniformity of the lithium deposition-dissolution process.When the lithium deposition is uniform, the metal lithium can largely prevent corrosion during the cycling process, so that the lithium electrode can achieve better cycling efficiency.

3 lithium, lithium ion can occur through the SEI film deposition and dissolution process, but in the process of dissolution and deposition, because of the important composed of ionic components of SEI is difficult to adapt to the process of lithium surface morphology change, therefore the SEI film ruptures, lead to the emergence of the nude lithium and its further reaction of the electrolyte, so repeated deposition in lithium - solvent thermal process, lithium and electrolyte composition is consumed, lead to lithium electrode cycle performance attenuation.

4, the SEI film breakdown can lead to form some highly active, so as to accelerate the deposition of these sites lithium and solvent speed, leading to lithium electrode surface current distribution inhomogeneity, inhomogeneity and dendrite formation leads to a series of security problems, this is the commercialization of metallic lithium battery application was the important reason for the failure.