First-Principles Studies Of Lithium Intercalation Behavior Into Graphite As Anode Materials For Lithium Ion Batteries

The first-principles pseudopotential method within the generalized gradient approximation (GGA) based on the density functional theory (DFT) are employed to investigate lithium intercalation behaviors in graphite and lithium adsorption on graphene.1. The geometric and electronic structures of bulk graphite, which is an important anode material for lithium ion batteries, are studied. The atomic structures are optimized, the density of states (DOS) and band structure are presented, and the average lithium intercalation voltage is calculated. The results show that graphite reaches the most stable state by changing the length of C-C layers and C-C bonds. Pure graphite and its lithium intercalated compounds are all good conductors. The voltage is close to 0 V when the intercalation state comes to Li₆C₃₆, which illuminates that LiC₆ is the theoretical limit of graphite intercalating by lithium. This agrees well with experimental results.2. The geometric and electronic structures of graphene are then calculated, in order to study its potential application as anode materials for lithium ion batteries. The atomic structures, DOS, band structures and lithium adsorption energies are calculated. Results show that the lithium adsorption energy reaches a lowest value when the adsorption height is 1.71?. The calculated DOS shows that the graphene adsorbed with lithium exhibits metallic electronic structure.