Effect of different charge rates on the active material lithiation of Gr/SiOx blend anodes in lithium-ion cells

Anodes with blended active materials, containing SiOx as a secondary material in addition to graphite, gain interest in research and commercial applications to increase the capacity of lithium-ion batteries. SiOx has the advantage of significantly higher specific capacity than graphite but the disadvantage of a reduced cycling and structural stability. To understand the processes involved for this type of blend anode, a detailed investigation of its electrochemical behavior is required. This work provides a non-destructive method for understanding the interaction between blend materials in cells containing silicon-based active material. This method helps to identify internal battery conditions and thereby optimize the battery performance. A cylindrical cell containing approximately 10 wt% of SiOx is used for electrochemical testing. By analyzing the voltage hysteresis, differences in the graphite lithiation are observable, which allows conclusions to be drawn about the SiOx lithiation. An increase in the charge rate leads to a decrease in graphite lithiation and consequently to an increase in SiOx lithiation. This effect is explained by the analysis of the pure material anode potentials. Validation of the effect is given by X-ray diffraction analysis to identify the state of graphite lithiation.