Anode materials discovery examples
1.) Understanding ion intercalation and degradation mechanisms
Charge photometry provided new insights into the impact of fast charging on a newly developed anode material, Nb14W3O44 (NWO).
Charge photometry provided new insights into the impact of fast charging on a newly developed anode material, Nb14W3O44 (NWO).
Intensity gradients build up along the rod-shaped NWO particle, starting at the ends and moving in towards the centre within the first 60 seconds of lithiation (cycled at 2C). At this stage, the active particles retain mechanical integrity.
Increasing the cycling rate to 5C induces rapid cracking. As before, ion concentration gradients develop along the particles; however, in this case, the resulting internal stresses and strains – caused by the formation of Li-rich and Li-poor domains – are sufficient to fracture the particle.
Particle fracture can contribute to capacity loss by depleting the lithium inventory – a phenomenon observed in this case as well. The figure on the left displays images of the delithiated electrode, where fractured particles contain brighter fragments. The greater intensity indicates they contain trapped lithium, suggesting they have become electrically isolated from the rest of the electrode, ultimately leading to capacity loss.
Charge photometry was used to determine the volume changes of individual silicon particles during lithiation and delithiation and to assess if such particles could expand and contract without pulverising or cracking.
An active particle of nanoporous silicon is expanding in size during lithiation and contracting during delithiation (battery cycled at a C/10 rate to 1000 mAh/g and video shown is of the second electrochemical cycle). The overall shape of the particle is preserved, without any observable pulverisation or cracking. The same behaviour was observed in subsequent cycles, including at higher C-rates, suggesting that the active material is structurally robust. More detailed information relating to this example can be found in the following application note.
With a detailed knowledge of material behaviour, researchers can make informed decisions on how to mitigate degradation pathways earlier on in the discovery process, accelerating the development of new anode materials.
Charge photometry provides:
It is an operando technique, enabling rapid, dynamic processes to be visualised in real time
See what conditions cause material degradation by observing particle fracture as it occurs