Mechanical properties and role of 2D alkynyl carbon monolayers in the progress of lithium-air batteries

Abstract

Lithium-air batteries (LABs) have been proposed as power sources for developing electric vehicles due to their high theoretical capacity. The cathode of these batteries is typically constructed based on porous carbon allotropes. Two-dimensional (2D) alkynyl carbon materials (D-graphyne, P-graphyne, and QC-graphyne), show remark structure features and can provide a unique opportunity for designing the air cathode of the LABs. However, the physical characteristics of these 2D carbon monolayers have not been clear completely studied as air cathodes. Hence, in the current study, the effect of length, strain rate, temperature, and (CH3)2OS/LiPF6 non-aqueous electrolyte with 1 Molar concentration on mechanical features were investigated for 2D alkynyl sheets using molecular dynamics simulation. The results show that the mechanical stability is in the order of D- > P- > QC-graphyne, and the percentage difference of mechanical properties in the presence and absence of electrolyte is <13 % at 300 K. These results are proper for an air cathode because they reveal that the electrolyte cannot lead to significant mechanical weakness. The lithium diffusivity increases in the presence of 2D alkynyl carbon allotropes due to interfacial interactions. Moreover, 2D alkynyl monolayers provide the features of 2D graphene and γ-graphyne for lithium diffusivity that is essential due to high mechanical stability and ultrahigh capacity, respectively. The provided insight by this study highlights the 2D alkynyl monolayers which are more probable to be experimentally synthesized than other 2D graphyne families and show more desired physical characteristics for designing the air cathodes and decreasing charging time.