Scientists of the Energy’s Lawrence Berkeley National Laboratory have gained a closer look on electrochemical processes within cathode particles during charging and discharging.
Thanks to highly advanced visualization techniques, the team of Guoying Chen, leader of the Berkeley research project, is now able to describe the dynamic reaction pathways inside charging and discharging lithium-ion batteries more precisely.
In order to demonstrate phase transformation processes in the battery, the scientists used the particularly advanced battery material of a lithium manganese nickel oxide cathode and examined it with a combination of transmission microscopy and X-ray absorption analysis. After that, they visualized the electrochemical processes at a very high spatial resolution to get a deeply insightful view on nucleation and growth during the chemical and phase distribution on their particles.
This new perspective led to new knowledge about the causes of fade in long-term battery cycling. The Berkeley scientists found out that the impact of volume differences between the phases led to a cracking of the particles. Guoying Chen explains: “If you have cracking, it means fresh surface keeps getting exposed, thus causing more reactions with the electrolyte, which consumes the electrolyte and reduces the lifetime of the battery,” and “If we can minimize or eliminate the cracking issue, we probably will see much improved stability.”
Two ways of approach seem to be a conceivable solution to the problem at the moment: Using smaller particles or avoiding to fully charge the particles; however, the researchers are also looking for further strategies.
Image Source: Marilyn Chung / Berkeley Lab | newscenter.lbl.gov