A nodal flexible-surface three-dimensional carbon network with potential applications as a lithium-ion battery anode material

Topological semimetals (TSMs) with nodal flexible-surfaces are currently garnering paramount importance due to their exceptional electronic properties. However, nodal flat-surfaces and nodal spheres have only been observed in a few quantum models due to strict symmetry constraints. In this study, we introduce a cyclooctatetraene (COT)-based novel three-dimensional (3D) carbon network using density functional methods. Computational results show that the novel 3D COT network is dynamically stable and exhibits a linear dispersion relation near the Fermi level. Remarkably, the 3D band spectrum of the COT network exhibits a rare crossbar-like topological nodal flexible-surface. We identify key factors behind the emergence of a nodal flexible-surface using the analyses of orbital-projected band structures, tight-binding electronic bands, atom/orbital-projected density of states and band-decomposed charge densities. The pi-bonding and anti-bonding orbitals of C atoms predominantly contribute to the origin of topological semimetallic properties. Fermi velocities of holes and electrons (similar to 2.01-8.70 x 106 m s-1) in the 3D COT network are found to be higher than that of graphene along specific crystallographic directions. Furthermore, we have investigated the application of the 3D COT network as an anode material for Li-ion batteries. Our findings indicate that the 3D COT network shows promise as the anode in the Li-ion batteries due to its low energy diffusion barriers (0.008-0.68 eV), enabling rapid charge-discharge rates. Additionally, it exhibits a higher theoretical specific capacity (627.5 mA-1 h g-1) compared to graphite and an optimal average open circuit voltage of 0.85 V. This study introduces a novel three-dimensional carbon network based on cyclooctatetraene (COT), featuring a rare crossbar-like topological nodal flexible-surface and potential applications in Li-ion battery anodes.