Influence of the ink’s solid fraction and composition on Si anodes electrochemical performances

Abstract

In the field of lithium-ion batteries, silicon is a very promising anode active material because its theoretical specific capacity is ten times the one of graphite used in current commercial lithium-ion batteries. However, the large volume expansion of silicon during lithiation (~300% vs. 7% for graphite) causes electrode cracking/delamination, which significantly affects its electrochemical performance. The objective of this thesis is to determine the influence of the ink’s solid fraction and its composition on the Silicon anode’s electrochemical performances.

On one hand, this project has highlighted that the solid fraction modifies the rheological properties of the ink and thus, its viscosity. The viscosity greatly influences the homogeneity of the electrodes. This phenomenon seems to have repercussions on the electrochemical performances, decreasing the capacity retention.

On the other hand, the modification of the ink’s composition with the insertion of a reticulation additive (ZnSO4) appears to decrease the viscosity of the ink. This decrease in viscosity is highly likely due to a folding of the polymeric chains of the binder. This folding greatly improves the homogeneity and stability of the electrodes. The results obtained by cycling the electrodes with ZnSo4 demonstrated a high specific capacity, the same for every formulation, regardless of the solid fraction.