Experimental Analysis of the Current Distribution between Graphite and SiOx in Blend Electrodes for Lithium-Ion Cells

Abstract

The demand for battery cells with increased energy density without sacrificing performance is driving research into investigating new active electrode materials. The addition of silicon oxide as a second active anode material alongside graphite, referred to as graphite/SiOx blend electrodes, offers a great opportunity to increase the specific capacity of lithium-ion cells. The stable structure of graphite in combination with the high theoretical capacity of silicon represents a promising improvement, for example to increase the driving range of electric vehicles.In this work, the electrochemical behavior during the lithiation and delithiation process of blend electrodes is analyzed. Two custom-made cells are connected in parallel, with each of the cells containing either pure graphite or pure SiOx as the working electrode. Both cells use similar counter electrodes. The experimental setup enables the measurement of the current distribution during charging or discharging of the parallel connection. The observed individual current flow to each cell represents the current flow to each active material. This allows conclusions to be drawn about of the electrochemical processes in a graphite/SiOx blend electrode [1].This work focuses on two effects of blend electrodes: First, the lithiation differences between the active materials with increasing charge rates. Changes in the lithiation distribution between the active materials are observed at higher currents. Second, the effect of hysteresis on the lithiation of blend electrodes. When stating the lithiation process with a fully or partially delithiated blend electrode, the increased delithiation potential of SiOx [2] causes differences in the lithiation distribution between the materials. The knowledge gained on graphite/SiOx blend electrodes contributes to a better understanding of lithium-ion cells and to the optimization of their integration in electric vehicles.