Three-Dimensional Porous Particles Composed of Curved, Two-Dimensional, Nano-Sized Layers for Li-Ion Batteries

Building on previous knowledge acquired through research on thin-film batteries, three-dimensional (3D) porous macroscopic particles consisting of curved two-dimensional (2D) nano-structures of Si may bring unique advantages for Si anode technology. Prior work on thin Si films showed that during Li insertion, large-area Si films mostly accommodate the volume changes via variation in thickness. Therefore, the changes in the external surface area can fundamentally be minimized and thus, formation of a stable, solid electrolyte interphase (SEI) should be easier to achieve. In contrast, Si nanoparticles expand uniformly in all dimensions and thus, their outer surface area (where SEI forms) changes dramatically during insertion/extraction of Si. The low elasticity of the SEI makes it difficult to achieve the long-term stability under cycling load. Further, thin Si films have lower surface area (for the same mass), in comparison to Si nanoparticles, and better potential for achieving low irreversible capacity losses on the first and subsequent cycles.