How silicon electrodes can be calendered without altering their mechanical strength and cycle life

The calendering of Si-based electrodes is required to obtain a substantial gain in their volumetric capacity compared to conventional graphite electrode. However, as shown in the present study performed on silicon/carbon nanoplatelets/carboxymethyl cellulose electrodes, their calendering induces a major decrease of their cycling stability. This can be attributed to the rupture of the particle-binder bridges during the calendering, lowering the mechanical strength of the electrode. It is found that these cohesive bonds can be restored through an appropriate post-calendering treatment (called maturation). It consists of storing the calendered electrode in a humid atmosphere for a few days before drying and cell assembly. From in-operando dilatometric experiments, it appears that the volumetric expansion is lower and more reversible than for a standard (not-calendered, not-matured) electrode. As a result, a remarkable improvement of the cycle life is observed. However, when cycled in Si/NMC full cell, a rapid capacity decay is observed because of the SEI instability.