Effects of the Formulations of Silicon‐Based Composite Anodes on their Mechanical, Storage, and Electrochemical Properties

In this work, the effect of the formulation of silicon-based composite anode on its mechanical, storage and electrochemical properties was investigated. The formulation of the electrode was changed by using hydrogenated or modified (through covalent attachment of a binding additive eg. polyacrylic acid) silicon and acetylene black or graphene sheets, as conducting additive. We found that the composite anode with the covalently grafted binder has the highest elongation without break and strong adhesion to the current collector. It was also found that these mechanical properties are significantly dependent on the conductive carbon additive used and that the use of graphene sheets instead of acetylene black can significantly improve elongation and adhesion. Upon storage at ambient conditions during 180 days, the electronic conductivity and discharge capacity of the modified silicon electrode showed a much smaller decrease than the hydrogenated silicon composite electrode suggesting that the modification can play a passivation role to maintain a constant active material composition. Moreover, it was shown that this composite Si anode has high packing density and consequently thin film electrodes having a very high material loading can be prepared without penalizing its electrochemical performance.