2D Squaraine‐Linked Polymers with High Lithium Storage Capacity Using the First Principle Methods

Abstract

AbstractLithium storage in two‐dimensional squaraine‐linked covalent organic frameworks (2D SQ‐COPs: SQ‐COP‐1, SQ‐COP‐2 and SQ‐COP‐3, respectively constructed by squaraine linker and small heterocyclic molecule nodes B3O3, H3B3N3 and C3N3), have been studied by using the first principle methods. For the adsorption of multiple Li atoms, there is no Li2 dimer or cluster formation in SQ‐COPs, but Li−O bonds formation in SQ‐COP‐1 and SQ‐COP‐3. Accumulated Li atoms in Lin@SQ‐COPs will be arranged to produce regular 2D hexagonal packed configurations due to the effects of confined space. Bader analysis reveals charge transfer from Li atoms to SQ‐COPs, indicating high lithiation. Among 2D SQ‐COPs, SQ‐COP‐1 shows better conductivity than SQ‐COP‐2, and maintains stable adsorption configuration compared with SQ‐COP‐3. Furthermore, dynamical calculations indicate that Li atom prefers to move across the 1D pores of SQ‐COP‐1, overcoming a very low energy barrier, which further enhances Li storage capacity. Such good Li storage capacity in 2D metal‐free SQ‐COPs might lead to a promising and environmental‐friendly application in Li ion batteries.