Comprehensive Understanding of Reduction Mechanisms of Ethylene Sulfite in EC-Based Lithium-Ion Batteries
2019
Ren, Fucheng | Zuo, Wenhua | Yang, Xuerui | Lin, Min | Xu, Liangfan | Zhao, Wengao | Zheng, Shiyao | Yang, Yong
The reliable electrolyte additives are critically important to satisfy the rapidly increasing demand for electrical energy storage with safety, low cost, long life, and high-energy/power density. As an effective electrolyte additive, ethylene sulfite (ES) is widely used in lithium-ion batteries to improve their cycling performance at low temperature. However, its working mechanism, particularly in ethylene carbonate (EC)-based electrolyte, is still elusive. Here, we present a comprehensive theoretical study of the reduction mechanism of ES in EC-based electrolyte with the ring-opening reaction followed by dimerization reaction and/or the second-electron reduction path. The effects of participation of cosolvents such as diethyl carbonate (DMC), ethyl methyl carbonate (EMC), and dimethyl sulfite (DMS) on the ring-opening reaction process of ES were also carefully investigated. Based on our calculation results, the reactivity order of the clusters (ES)Li⁺(M) (M = EC, PC, VC, DMC, DMS, and EMC) is shown as follows: (ES)Li⁺(VC) (4.09 × 10⁵⁵ s–¹) > (ES)Li⁺(PC) (9.21 × 10⁴⁷ s–¹) > Li⁺(ES) (8.47 × 10⁴⁷ s–¹) > (ES)Li⁺(EC) (7.07 × 10⁴⁷ s–¹) > (ES)Li⁺(DMS) (3.11 × 10⁴³ s–¹) > (ES)Li⁺(EMC) (1.91 × 10⁴¹ s–¹) > (ES)Li⁺(DMC) (2.48 × 10³⁷ s–¹). The implication of our calculation results on the formation of SEI on the graphite is also discussed.
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