Researchers at Ritsumeikan University have used operando synchrotron X-ray tomography to capture the three-dimensional behaviour of silicon anodes in all-solid-state batteries (ASSBs).
Their study reveals how silicon retains partial ionic contact with solid electrolytes, even as it undergoes dramatic expansion and contraction during cycling.
Silicon offers far higher lithium storage capacity than graphite, but its volume can increase by around 410% during charging. This swelling often cracks particles and weakens contact with the electrolyte, reducing efficiency.
To investigate, a team led by Professor Yuki Orikasa, with Mao Matsumoto and Dr Akihisa Takeuchi, built a specially designed cell using the sulfide-based electrolyte Li6PS5Cl. Their operando imaging showed that while voids form around shrinking silicon particles, thin electrolyte layers remain adhered, acting as bridges that preserve ion pathways.
“The insights obtained in this study, including the identification of nanoscale interfacial separation phenomena and their effect on ionic transport, deepen our understanding of the chemomechanical interplay in Si-based ASSBs and provide guidance for the design of more robust, high-capacity composite electrodes,” said Professor Orikasa.
Nano-computed tomography revealed that detachment follows an anisotropic pattern: separation begins along particle sides, while vertical regions remain connected. This directional delamination allows lithium ions to continue flowing, explaining why performance stabilises after early cycles. Residual fragments of electrolyte containing sulphur and phosphorus were also found adhering to silicon surfaces, providing further anchoring points.
Mao noted, “The findings suggest that not all interfacial separation is harmful; partial and directionally constrained delamination can coexist with stable performance if the electrolyte retains limited but continuous pathways for ion transport.”
