A New sp²–sp³-Hybridized Metallic Carbon Network for Lithium-Ion Battery Anode with Enhanced Safety and Lithium-Ion Diffusion Rate

Abstract

Carbon-based materials play a significant role in the development of the next-generation lithium-ion battery technologies. However, the commercial use of anodes has been obstructed by their volume expansion and poor rate performance during the lithiation/delithiation process. Here, by means of first-principles calculations, we identify two hitherto unreported sp2–sp3-hybridized carbon allotropes, D10 and D14 carbon, with space groups Pmma and Pmm2, respectively. Interestingly, D14 carbon is predicted to be metallic with high electron density near the Fermi level. We then demonstrate that this metallic D14 carbon is a possible anode material in lithium-ion batteries: it is found that the energy barrier along the two inequivalent migration paths in D14 carbon is 0.38 (2.28) eV, which is lower than that of the recently reported bco-C16 structure with energy barriers of 0.53 (2.32) eV. Moreover, benefiting from the existence of sp3-hybridized network in D14 carbon, during the process of charging/discharging, Li diffusion routes are robust against the mechanical deformation. Therefore, as compared to graphite, this D14 anode show many advantages in lithium-ion battery applications, such as lower Li diffusion barrier, moderate theoretical capacity (319 mA h g–1), lower average open circuit (0.53–0.20 V), and enhanced safety features (only 3.6% volume expansion with full Li insertion).