Breaking the lithium storage limit via independent bilayer units within 2D layer materials

The study of Kühne et al. has identified lithium intercalation into independent bilayer graphene sheets by in-situ low-voltage (80 kV) TEM combined with both spherical and chromatic aberration correction. The breakthrough lies in a multi-layered close-packed Li superdense phase found in the bilayer graphenes. Based on this superdense phase, a larger expected lithium storage amount, which far exceeds that in the LiC6, was obtained. Bilayer graphene sheets, as the smallest units for the lithiation process, obtained a free expandable space without resistance from the adjacent graphene layers. If the bilayer unit was reproduced as a basic module of electrode materials, a designed architecture with countless independent bilayer units can be assembled to store more Li. Also, the bilayer graphene units can also obtain a higher ionic and electronic conductivity, owing to the decreased Coulomic repulsion and steric hindrance. The bilayer structure represents a new understanding of the nanocrystallization of two-dimensional materials.