Diffusion Enhancement to Stabilize Solid Electrolyte Interphase

The damage of the solid electrolyte interphase (SEI) layer during the stripping process in lithium secondary batteries causes the reduction of energy density. The stabilization of the solid electrolyte interphase is as important as the inhibition of lithium dendrites for lithium-based batteries. But the former is largely underestimated, which leads to the unclear damage mechanism and the lack of effective solutions to suppress the damage. Here, in this paper a diffusion-limited damage mechanism of the SEI layer is proposed. The inhomogeneity of the SEI layer results in region-dependent diffusion kinetics of lithium ions (Li+) passing through the layer. The slip lines and kinks having a thicker SEI layer, show slower Li+ conduction than the smooth surface. The uneven stripping process leads to the formation of cracks at the boundary between the slip lines and the smooth surface, which further causes collapse and serious damage of SEI. Upon this assumption, it is proposed to enhance the diffusion of Li+ at the local areas of SEI layer by applying parallel magnetic fields on the outside of electrodes. Both the electrochemical characterizations and long-term stability examination confirm the effectiveness of the magnetic field in enhancing the diffusion of Li+ and suppressing the damage of SEI.