Enabling Fast-Charging and High Specific Capacity of Li-Ion Batteries with Nitrogen-Doped Bilayer Graphdiyne: A First-Principles Study

Abstract

Carbon-based materials are the most important anode materials for Li-ion batteries (LIBs). To improve the electrochemical performance of LIBs for high energy density and fast charging, advanced carbon allotropes are in the research focus. In this work, we applied the density functional theory to investigate the atomic and electronic structures as well as high Li-ion specific capacity of graphdiyne (GDY). The atomic structures of monolayer graphdiyne (MGDY), bilayer AB(β1)-stacking graphdiyne (AB(β1)BGDY) and nitrogen-doped AB(β1)BGDY (N-AB(β1)BGDY) at different lithiation states were thoroughly investigated. The AB(β1)BGDY and N-AB(β1)BGDY exhibit promising characteristics in Li-ion adsorption and intercalation, enhancing its specific capacity from 744 mAhg-1 in the monolayer GDY to 807 mAhg-1 in the bilayer. Besides increasing the capacity through a bilayer-structure, it is possible to tailor its structural stability and band gap by doping. Especially shown for N-AB(β1)BGDY (~1%), an increased structural stability and a decreased band gap of 0.24 eV is found. While this means that N doping in AB(β1)BGDY can lead to longer-lasting and more stable operatable high-capacity anodes in LIBs, it increases the OCV.