Novel two-dimensional C6B4 monolayer as an anode for Li-/Na-ion batteries with high theoretical capacity

Abstract

In this study, we predict a two-dimensional (2D) multi-ring structure composed of carbon and boron atoms by first-principles calculations, and investigate its potential for lithium/sodium storage. The cells in this structure are composed of six carbon and four boron atoms (hence the name k-C6B4). Its stability as well as mechanical, electronic, and energy storage-related properties are also investigated. The results show that k-C6B4 has a high density of states of 0.328 states/eV/atom at the Fermi level, with maximum values of the Young's modulus and Poisson's ratio of 272.39 N/m and 0.4, respectively. This shows that k-C6B4 has good electrical conductivity and mechanical ductility such that it can avoid damage during the charging and discharging processes. Moreover, the barriers to the diffusion potential of k-C6B4 for the Li and Na ion were 0.195 eV and 0.123 eV, respectively, which are important for efficient charging and discharging. Most importantly, k-C6B4 has a high specific capacity of 1395 mAhg−1 for Li/Na ions. These findings suggest that the 2D k-C6B4 is a promising anode material for LIBs/NIBs, and provides a new strategy for energy storage.