Abstract
From first principles calculations, a novel pentagonal Si/C complexity is predicted to have potential applications as a promising anode material for Li-ion batteries. It is found that the structural and thermal stability of the penta-siligraphene (P-Si2C4) is better than penta-graphene that is composed of C atoms only. Electronic band structure analysis shows that the empty C-2pz state in the P-Si2C4 provides space to accommodate and stabilize electrons from Li, which makes Li storage energetically favorable. As a result, four Li atoms can be stored by one formula unit of the P-Si2C4, corresponding to a theoretical gravimetric Li storage capacity of 1028.7 mAhg−1. The metallic electronic structures of the Li-adsorbed P-LixSi2C4 as well as very small Li migration energy barriers are beneficial for fast charge/discharge performance of the battery. The mechanism on the Li adsorption interaction on the P-Si2C4 is discussed. These results demonstrate a novel strategy to design two-dimensional Si/C complex anode materials for high-performance Li-ion batteries.
Highlights
The relatively low energy density of the currently commercialized Li-ion batteries (LIBs) is difficult to meet the requirement of the commercial electric vehicles (EVs) and becomes a big challenge for the development of the EV industry [1, 2]
The predicted high Li storage capacity is attributed to the enhanced Li adsorption interaction with the siligraphene monolayer, which is related to the changes of Si atom from sp2 to sp3-like [13]
The projector augmented wave (PAW) method [34, 35] combined with the general gradient approximation (GGA) exchange and correlation functionals parameterized by Perdew-Burke-Ernzerhof (PBE) are used [36]
Summary
The relatively low energy density of the currently commercialized Li-ion batteries (LIBs) is difficult to meet the requirement of the commercial electric vehicles (EVs) and becomes a big challenge for the development of the EV industry [1, 2]. Due to its very good cycling performance, graphite is the most widely used anode material, but its theoretical gravimetric capacity (372 mAhg−1) is relatively low [3, 4]. Silicon has extremely high theoretical gravimetric capacity of about 4200 mAhg−1 [5], but the cycling performance is poor due to its very large volume expansion up to 420% at fully lithiated state [6]. Lin et al had shown that 2D SiC sheets can be prepared through solution exfoliation techniques [11] They successfully prepared quasi-2D SiC2 sheets which can be preserved in air for months [12]. First principles calculations suggest that siligraphene is a promising anode material that offers a theoretical capacity of 1520 mAhg−1 and 1286 mAhg−1 for g-SiC5 and g-SiC2, respectively [13]. The electronic configuration change from sp to sp3-like is accompanied by obvious structural changes during Li adsorption on the siligraphene
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