Journal of Power Sources, Vol.391, 80-85, 2018
Determination of the mechanical integrity of polyvinylidene difluoride in LiNi1/3Co1/3Mn1/3O2 electrodes for lithium ion batteries by use of the micro-indentation technique
Understanding the mechanical aging of lithium ion batteries influencing the binder stability is of particular interest for enhanced battery life. In this study we present an indentation method to investigate the changes in the elasticity of PVdF in NCM electrodes with high reproducibility. To determine changes in elasticity by calculating the indentation work (eta(it)), a 50 gm flat punch indenter was used. In addition, a drying procedure for DMC washed samples was evaluated to reduce the effect of the washing procedure on the elasticity due to swelling of the binder. NCM electrodes soaked with electrolyte and electrodes after formation were investigated, showing a significant decrease in elasticity due to the contact with the LiPF6 containing organic carbonate solvent based electrolyte and due to the electrochemical formation procedure. Further electrochemical aging reduced the elasticity to nearly,approximate to 50% compared to the pristine electrode. Method development and the obtained results are discussed in detail. The developed method provides a low standard deviation and high reproducibility. Hence, it is a valid methodology for the quantification of related aging mechanisms taking place in lithium ion batteries.