Understanding the calendering processability of Li(Ni0.33Mn0.33Co0.33)O2-based cathodes

The calendering process aims at enhancing the electrode energy density, and improving the electronic conductivity, and determines the final porous electrode micro/mesostructure. In this sense, one of the main parameters of interest is its impact in the electrode porosity (ε) and the electrochemical performance. Here, we present a systematic study of the calendering conditions (applied calender pressure and roll temperature) effect on the final NMC-based electrodes ε in terms of the active material/carbon additive/binder composition and the amount of solvent used during the preparation of the slurries. The calendering processability was assessed through the cathodes compressibility resistance and minimal attainable ε, the electrode mechanical properties (hardness and elastic deformability), the pore size distribution, the electrode film mesostructure and the C-rate cathode electrochemical performance. Based on our results, it was found that the distribution and organization of the inactive carbon black (CB)/PVdF phase and the electrode mesostructure are the key parameters that control the cathode processability through calendering. Electrodes with high CB/PVdF content and prepared with higher amounts of solvent in the slurry ensure a good electronic conductivity and a film-like structure of the electronic conducting phase around the NMC particles which upon calendering outputs a better electrochemical performance.