Atia Tasfiah Azad

• Azad, Atia; Bateman, Katherine; Irvine, Matthew; Naden, Aaron B.; Dickson, Stewart A. M. & Smith, Ronald I. [Show all 8 contributors for this article] (2025). Thermal expansion of lithiated silicon (Li13Si4 and Li7Si3) anodes: a powder neutron diffraction study. Journal of Materials Chemistry A. ISSN 2050-7488. 13(20), p. 14836–14845. doi: 10.1039/d4ta07858f. Full text in Research Archive Show summary

  Whilst at room temperature structural changes on lithiation of the silicon electrode are hard to study due to formation of amorphous phases, at high temperatures, used in thermal batteries, clear phase changes linked to voltage plateaux are observed. Here we report results from a galvanostatic discharge of a FeS2/LiCl–KCl/Li13Si4 cell at 500 °C. The cell discharge showed a flat voltage plateau between Li13Si4 and Li7Si3 which indicates that both phases are in equilibrium and are line phases. In situ powder neutron diffraction study of two lithiated phases of silicon, Li13Si4 and Li7Si3, was performed. The two phases were heated from room temperature to 500 °C. This showed the phases did not become amorphous and did not undergo phase changes, with both phases being remarkably stable. The variation with temperature of the unit cell parameters was linear. The volumetric thermal expansion coefficient of Li13Si4 is 99.3 × 10−6 °C−1 and Li7Si3 is 106 × 10−6 °C−1. The volumetric thermal expansion of the two phases is significantly larger than that of silicon and closer to the thermal expansion of lithium metal. Thus, the LixSi electrode is mechanically closer to lithium than to silicon, and it can be considered as silicon clusters embedded within the lithium array rather than the silicon lattice hosting lithium.

View all works in NVA