Abstract
Sulfur cathodes in lithium-sulfur (Li-S) batteries still suffer from their low electronic conductivity, undesired dissolution of lithium polysulfide (Li2Sn, 3 ≤ n ≤ 8) species into the electrolyte, and large degree volume change during the cycle. To overcome these problems, an effective encapsulation for the sulfur cathode is necessary. By means of particle swarm optimization (PSO) and density functional theory (DFT), we have predicted a stable metallic two-dimensional sp2-hybridized carbon allotrope (DHP-graphene). This carbon sheet can prevent S atoms from cathode entering electrolyte. However, Li-ions can shuttle freely due to the increasing difference in Li-ions concentration between electrolyte and cathode along with the potential difference between cathode and anode during charge-discharge cycles. In addition, versatile electronic band structures and linear dispersion are found in DHP-graphene nanoribbons but only metallic band structure occurs for DHP-graphene nanotubes.
Highlights
Our Density functional theory (DFT) calculations show DHP-graphene could be used as a filter to encapsulate the cathode of Li-S batteries due to its decagon carbon rings
Density functional theory (DFT) calculations were carried out using general gradient approximation (GGA)[39] as implemented in the Vienna ab initio simulation package (VASP)[40,41]
The interactions between the nucleus and valence electrons of carbon were described by the projector augmented wave (PAW) method[42]
Summary
The main purpose of this study is to demonstrate the feasibility of alleviating the shuttle phenomenon and maintaining high electrical conductivity at the same time by using this novel carbon allotrope as the cathode of Li-S batteries
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