A Facile and Very Effective Method to Enhance the Mechanical Strength and the Cyclability of Si-Based Electrodes for Li-Ion Batteries

It is well known that the mechanical properties of lithium-ion battery electrodes impact their electrochemical performance. This is especially critical for Si-based negative electrodes, which suffer from large volume changes of the active mass upon cycling. Here, this study presents a postprocessing treatment (called maturation) that improves the mechanical and electrochemical stabilities of silicon-based anodes made with an acidic aqueous binder. It consists of storing the electrode in a humid atmosphere for a few days before drying and cell assembly. This results in a beneficial in situ reactive modification of the interfaces within the electrode. First, the binder tends to concentrate at the silicon interparticle contacts. As a result, the cohesion of the composite film is strengthened. Second, the corrosion of the copper current collector, inducing the formation of copper carboxylate bonds, improves the adhesion of the composite film. The great improvement of the mechanical stability of the matured electrode is confirmed by in-operando optical microscopy showing the absence of film delamination. The result is a significant electrochemical performance gain, up to a factor 10, compared to a not-matured electrode. This maturation procedure can be applied to other types of electrodes for improving their electrochemical performance and also their handling during cell manufacturing.