Negatively curved carbon as the anode for lithium ion batteries

Abstract

The inclusion of heptagonal, octagonal, or larger rings in an sp2-bonded carbon network introduces negative Gaussian curvature that can lead to a high network porosity. Here we investigated a particular negatively curved nonplanar sp2-carbon structure namely 688P schwarzite, with a view toward the possible use of negatively curved carbons as lithium ion battery anodes. Our first principles calculations show that the presence of pores in schwarzites can lead to three-dimensional Li ion diffusion paths with relatively small energy barriers. We calculated the binding energy of Li (which donates 1 electron to the schwarzite) in different positions in the schwarzite structure, and the open-circuit voltage (OCV) with respect to Li metal and found that this schwarzite has a positive OCV for a Li concentration as high as LiC4. The advantages of the particular schwarzite studied here for use as an anode are expected to be present in other sp2-bonded carbon networks that feature large polygonal rings.