Deciphering the Role of Fluoroethylene Carbonate towards Highly Reversible Sodium Metal Anodes
Xueying Zheng,
Suting Weng,
Wei Luo,
Bo Chen,
Xiao Zhang,
Zhenyi Gu,
Haotian Wang,
Xiaolu Ye,
Xuyang Liu,
Liqiang Huang,
Xinglong Wu,
Xuefeng Wang,
Yunhui Huang
Affiliations
Xueying Zheng
Institute of New Energy for Vehicles, Shanghai Key Laboratory of Development & Application for Metallic Functional Materials, School of Materials Science and Engineering, Tongji University, Shanghai 201804, China
Suting Weng
Institute of Physics, Chinese Academy of Sciences; School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
Wei Luo
Institute of New Energy for Vehicles, Shanghai Key Laboratory of Development & Application for Metallic Functional Materials, School of Materials Science and Engineering, Tongji University, Shanghai 201804, China
Bo Chen
Institute of New Energy for Vehicles, Shanghai Key Laboratory of Development & Application for Metallic Functional Materials, School of Materials Science and Engineering, Tongji University, Shanghai 201804, China; Key Laboratory of Advanced Civil Engineering Materials (Tongji University), Ministry of Education, Shanghai 201804, China
Xiao Zhang
Institute of Physics, Chinese Academy of Sciences; School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China
Zhenyi Gu
Key Laboratory for UV Light-Emitting Materials and Technology, Northeast Normal University, Ministry of Education, Changchun, Jilin 130024, China
Haotian Wang
Institute of New Energy for Vehicles, Shanghai Key Laboratory of Development & Application for Metallic Functional Materials, School of Materials Science and Engineering, Tongji University, Shanghai 201804, China
Xiaolu Ye
Institute of New Energy for Vehicles, Shanghai Key Laboratory of Development & Application for Metallic Functional Materials, School of Materials Science and Engineering, Tongji University, Shanghai 201804, China
Xuyang Liu
Institute of New Energy for Vehicles, Shanghai Key Laboratory of Development & Application for Metallic Functional Materials, School of Materials Science and Engineering, Tongji University, Shanghai 201804, China
Liqiang Huang
Institute of New Energy for Vehicles, Shanghai Key Laboratory of Development & Application for Metallic Functional Materials, School of Materials Science and Engineering, Tongji University, Shanghai 201804, China
Xinglong Wu
Key Laboratory for UV Light-Emitting Materials and Technology, Northeast Normal University, Ministry of Education, Changchun, Jilin 130024, China
Xuefeng Wang
Institute of Physics, Chinese Academy of Sciences; School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100190, China; Tianmu Lake Institute of Advanced Energy Storage Technologies Co., Ltd., Liyang, Jiangsu 213300, China
Yunhui Huang
State Key Laboratory of Materials Processing and Die & Mould Technology, School of Materials Science and Engineering, Huazhong University of Science and Technology, Wuhan, Hubei 430074, China
Sodium metal anodes (SMAs) suffer from extremely low reversibility (95% with conventional NaPF6 salt at a regular concentration (1.0 M). The peculiar role of FEC is firstly unraveled via its involvement into the solvation structure, where a threshold FEC concentration with a coordination number>1.2 is needed in guaranteeing high Na reversibility over the long-term. Specifically, by incorporating an average number of 1.2 FEC molecules into the primary Na+ solvation sheath, lowest unoccupied molecular orbital (LUMO) levels of such Na+-FEC solvates undergo further decrease, with spin electrons residing either on the O=CO(O) moiety of FEC or sharing between Na+ and its C=O bond, which ensures a prior FEC decomposition in passivating the Na surface against other carbonate molecules. Further, by adopting cryogenic transmission electron microscopy (cryo-TEM), we found that the Na filaments grow into substantially larger diameter from ~400 nm to >1 μm with addition of FEC upon the threshold value. A highly crystalline and much thinner (~40 nm) solid-electrolyte interphase (SEI) is consequently observed to uniformly wrap the Na surface, in contrast to the severely corroded Na as retrieved from the blank electrolyte. The potence of FEC is further demonstrated in a series of “corrosive solvents” such as ethyl acetate (EA), trimethyl phosphate (TMP), and acetonitrile (AN), enabling highly reversible SMAs in the otherwise unusable solvent systems.
