To facilitate the extensive application of pure electric vehicles, it is imperative to increase the energy density of the state-of-the-art lithium-ion batteries (200-250 Whkg-1). With its exceptionally low electrochemical potential and high theoretical specific capacity, lithium metal is considered one of the most promising next-generation anode for lithium battery systems. However, the severe safety issues caused by the distinctly high reactivity of lithium metal and the instability of lithium/electrolyte interface impede any feasible application of lithium metal batteries. Recently, researchers around the globe have been exploring methods to stabilize the lithium metal anode and the re-design of electrolyte is considered as the easiest and cost effective approach for the problem. Herein, we report a comprehensive study of assorted cyclic carbonates as solid-electrolyte interface (SEI) enabler for lithium metal batteries. A variety of cyclic carbonates including ethylene carbonate (EC), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoropropylene carbonate (TFPC), 4-(2,2,3,3,4,4,5,5,5-nonafluoropentyl)-1,3-dioxolan-2-one (NFPEC), and 4-((2,2,3,3-tetrafluoropropoxy)methyl)-1,3-dioxolan-2-one (HFEEC) were designed and synthesized. It was discovered that EC was not able to form a robust SEI on lithium metal surface and the Li/LiNi0.6Mn0.2Co0.2O2 (NMC622) cell employing EC-based electrolyte showed poor cycling performance. Although cyclic carbonates TFPC, NFPEC and HFEEC with fluoroalkyl or alkoxy substituents clearly did not offer extra stability over EC on the cycling of lithium metal, the fluorine-substituted FEC and DFEC provided superior protection on the cycling of lithium metal. The Li/NMC cells using FEC- and DFEC-based electrolytes displayed enhanced cycling stability and improved capacity retention over the cell employing EC-based electrolyte. Moreover, DFEC-based electrolyte noticeably outperformed FEC-based electrolyte in the cycling test of Li/NMC cells. In summary, DFEC was discovered as a novel SEI enabler for lithium metal anode and the robust SEI formed by the reductive decomposition of the DFEC drastically stabilizes the cycling of lithium metal batteries.

Selecting cyclic carbonate for high voltage lithium metal batteries

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.