Theoretical Study on the Role of Solvents in Lithium Polysulfide Anchoring on Vanadium Disulfide Facets for Lithium–Sulfur Batteries

Abstract

The shuttle effects by lithium polysulfides (LiPSs) and the sluggish reaction kinetics are crucial obstacles in the commercialization of Li–S batteries. Hence, effectively trapping and promoting the conversion of LiPSs is of prime importance. However, the fundamental kinetics of the electrocatalytic charging and discharging of Li–S batteries have not been sufficiently explored yet. Therefore, by taking VS2 as a model, we conducted a density functional theory-based study to investigate the ability of dominant exposed crystal planes of VS2 to trap LiPSs from leaching into electrolytes and to act as an electrocatalyst to increase the sulfur reduction reaction (SRR) kinetics. To reflect a realistic environment of a battery, the effect of solvents on the electrocatalytic activity was further investigated. Our calculations show that VS2 has moderate binding energy toward LiPSs; therefore, it can effectively inhibit LiPS shuttling and leaching. However, there was no consistent pattern for binding energies under different VS2 facets. Furthermore, VS2 (001) facets exhibit excellent electrocatalytic activity for the SRR and Li2S decomposition reaction compared to other dominant crystal planes, which significantly lowers the energy barriers of LiPS conversion during the charging and discharging process, ensuring high-rate performance and longer cycle life. Beyond the VS2 systems explored in the current study, the same approach can apply to other potential electrocatalysts as a promising pathway to improve the sluggish reaction kinetics of Li–S batteries.

Theoretical prediction of 2D biphenylene as a potential anchoring material for lithium–sulfur batteries

“…This interaction ultimately results in the formation of diverse LiPSs (Li 2 S n , n = 1, 2, 4, 6, and 8). 5 To explore the mechanism of the anchoring effects in the calculation, the configurations of S 8 and Li 2 S n ( n = 1, 2, 4, 6, and 8) are optimized firstly. As shown in Fig.…”

“…46–49 The rate-limiting step is the reduction process with the largest positive Gibbs free energy change. 5 In the following, the rate-limiting steps of the sulfur reduction reaction (SRR) are investigated using eqn (S1)–(S12) (ESI†). 5,42…”

“…5 In the following, the rate-limiting steps of the sulfur reduction reaction (SRR) are investigated using eqn (S1)–(S12) (ESI†). 5,42…”

“…[2][3][4] However, LIBs have faced many embarrassing problems, such as the high cost, scarcity of Li metal and low specific capacity, which make it difficult to meet the exigent demand of energy storage for today's industrial production and daily life. 5,6 Rechargeable Li-S batteries have been envisioned to possess ultra-high theoretical energy density (2600 W h kg À1 ) and theoretical specific capacity (1675 mA h g À1 ), [7][8][9] giving hope for a quantum leap in energy storage. The abundance of S as a raw material is a significant advantage of Li-S batteries, and the fact that S is inexpensive and environmentally benign further adds to its appeal.…”

Dynamic evolution of electrocatalytic materials for Li–S batteries

“…Thus, it is essential to utilize theoretical calculations to develop universal descriptors that describe the dynamic evolution process of electrocatalysts and reveal the universal laws of electrocatalyst evolution. Meanwhile, there exists a significant disparity between the static theoretical calculation model and the actual dynamic reaction process, 137 which requires more extensive exploration.…”