A New sp 2 –sp 3 -Hybridized Metallic Carbon Network for Lithium-Ion Battery Anode with Enhanced Safety and Lithium-Ion Diffusion Rate

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 sp 2 –sp 3 -hybridized carbon allotropes, D 10 and D 14 carbon, with space groups Pmma and Pmm 2, respectively. Interestingly, D 14 carbon is predicted to be metallic with high electron density near the Fermi level. We then demonstrate that this metallic D 14 carbon is a possible anode material in lithium-ion batteries: it is found that the energy barrier along the two inequivalent migration paths in D 14 carbon is 0.38 (2.28) eV, which is lower than that of the recently reported bco-C 16 structure with energy barriers of 0.53 (2.32) eV. Moreover, benefiting from the existence of sp 3 -hybridized network in D 14 carbon, during the process of charging/discharging, Li diffusion routes are robust against the mechanical deformation. Therefore, as compared to graphite, this D 14 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).