关键词: 固态锂离子电池, 界面接触面积比值, 电解质裂纹, 失效机制, 电化学阻抗谱模型

Abstract:

This study investigated the effects of porosity, crack shape, and interface contact area of solid electrolyte (SE) on solid-state batteries (STFLIBs). We used the resistance network method to model the microstructure of SE and a one-dimensional electrochemical coupled contact area model for SLIB. We established a one-dimensional electrochemical and two-dimensional SE resistance network model based on this physical model and conducted electrochemical impedance spectroscopy (EIS) simulation analysis. By inputting different electrolyte properties into the battery model, we predicted the effect of microstructure on battery capacity and impedance. The results show that within the range of 0°～90°, smaller crack angles have less impact on the conductivity of SE. To compare the effect of crack shape on electrical conductivity more conveniently, we kept the crack area unchanged. As the crack length increases, the electrical conductivity loss gradually increases until it reaches the extreme point after which the electrical conductivity loss starts to decrease. When the dimensionless length of the crack is <0.25, the conductivity loss caused by triangular cracks is lower than that caused by rectangular and elliptical defects. However, when the dimensionless length is >0.25, the influence of triangular defects exceeds than that of rectangular and elliptical defects. With the increase of porosity, the conductivity of SE rapidly decreases in an approximately linear manner. Electrolyte defects lead to a decrease in the discharge voltage of the battery, which is reflected in the EIS simulation as an increase in bulk resistance. The loss of interface contact area has a more significant impact on the loss of battery capacity, and this impact is significantly lower at low discharge rates compared to high discharge rates. Under different contact areas ( γ= 1.0 and 0.4), the specific capacity decreases by 60.08%, while at high magnification (50 C), the specific capacity decreases by 81.95%. The impact of interfacial area loss is relatively small when the magnification is low. The loss of interface contact area results in an increase in charge transfer impedance. When γ changes from 1 to 0.2, the charge transfer impedance increases by 25 times, and the average charge transfer impedance increases by 118.60 Ω for each 0.1 loss of contact area. Compared to electrolyte defects, the impedance increase caused by interfacial contact area loss is more significant. In practical applications, the battery can ensure high capacity performance only when the interface contact area is greater than 0.7. This study simulated the electrolyte interface contact factors that lead to an increase in SLIB impedance, thereby enriching relevant research in this field.

Key words: solid state lithium ion battery, interface contact area ratio, electrolyte crack, failure mechanism, electrochemical impedance spectroscopy model