Monitoring Li+ diffusion in MNC battery cathodes using TOF-SIMS

Revealing the nanoscale concentration distribution of Li ions within energy storage materials has remained a challenge for several decades, due to the weakness of interaction with X-rays and the impossibility of achieving the necessary real space resolution using neutron beams. Recently a major advance in this field has been made using Time-of-Flight secondary ion mass spectroscopy in conjunction with focused ion beam milling. It has been possible to obtain quantitiative nanometre resolution mapping of Li ion concentration in charged and discharge Li-rich battery cathodes (T. Sui et al., NanoEnergy, 2015). In the follow up to this study we performed time resolved experiments that reveal the pile-up of Li against internal obstacles, such as grain boundaries and cracks between primary particles. This insight has helped construct a damage cascade model to predict the battery performance degradation and capacity fading.