Silicon offers a much higher specific capacity than graphite, making it an attractive replacement for graphite in the negative electrodes of lithium-ion batteries. In theory, silicon could extend lithium-ion battery life tenfold. In research conducted under an EU project, scientists at Liten, a CEA Tech institute, studied silicon electrode aging mechanisms at the nanometric scale.

The researchers were able to look at aging mechanisms during battery operation, a first. Their observations revealed phenomena that had previously been underestimated. “We demonstrated that the main degradation mechanism is due to a lack of lithium, which is in turn caused by the lithium becoming trapped in parasite reactions,” said one of the researchers. The findings contradict previous research that pointed a finger at the negative impact of the solid electrolyte interface as one of the prime sources of degradation for this type of electrode. “In a half-cell configuration, the source of lithium is infinite, and skews how the results are interpreted. During actual battery operation, lithium loading is limited.”

The observation of whole cells was made possible by the effective combination of several imaging and spectroscopy techniques. This novel approach was one of the main factors that led to the groundbreaking findings.