First-Principles Plane-Wave-Based Exploration of Cathode and Anode Materials for Li and Na-ion Batteries

We present a first-principles study based on plane-wave derived Lowdin population analysis and other local bonding descriptors to investigate cathode and anode materials for lithium and sodium ion batteries. By comparing the Lowdin charges of common graphite-based anode materials such as LiC6 and LiC12 to other phases such as salts of dicyanamide and nanoporous carbon-based compounds, new conclusions of an improved intercalation behavior of the latter are derived. In addition, we explore the stability of the dicyanamide salts concerning the removal of Li and Na atoms from the compounds with some of them resulting in dimerized structures. In particular, having a look at the different kinds of bonds and the corresponding covalency indicators reveals new insights into the change of the bonds during dimerization. Considering the generally high thermal stability of metal dicyanamide salts, which are solid at room temperature, their electrochemical activity as well as non-toxicity of alkali metal-based compounds, these materials are potential alternatives to commercially available electrodes, particularly for sodium ion batteries, to pristine graphite-based anode materials.