期刊
ACS APPLIED MATERIALS & INTERFACES
卷 11, 期 27, 页码 23972-23981出版社
AMER CHEMICAL SOC
DOI: 10.1021/acsami.9b03279
关键词
ionic liquid; sodium ion battery; sodium manganese oxide; cathode electrolyte interfaces; solid electrolyte interfaces; X-ray photoelectron spectroscopy; sodium stripping plating
资金
- National Research Foundation (NRF, Singapore) [NRF2016NRF-NRF1001-22]
- International Centre for Energy Research (ICER)
The electrochemical performance of ionic liquid electrolytes containing different sodium salts dissolved in 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide (BMPTFSI) evaluated in a half-cell configuration using spherical P2-Na0.6Co0.1Mn0.9O2+z (NCO) cathodes are reported. Among the various electrolytes investigated, sodium bis(fluorosulfonyl)imide (NaFSI) (0.5 M) in BMPTFSI shows the best electrochemical performance with a significant improvement in cycling stability (90% capacity retention after 500 cycles at 50 mA g(-1) in a half cell versus Na metal anode) compared with conventional NaClO4 (1 M) in ethylene carbonate/propylene carbonate electrolytes (39% retention after 500 cycles). Cyclic voltammetry (CV) studies reveal that ionic liquid electrolytes are stable up to 4.8 V versus Na/Na+. When NaFSI and NaTFSI are used as conducting salts, X-ray photoelectron spectroscopy results prove that the cathode electrolyte interface (CEI) is composed of components resulting from the decomposition of the TFSI anion and the deposition of the BMP cation. On the other hand, the CEI layer of the electrode cycled in an electrolyte containing NaClO4 in BMPTFSI follows a different pathway of TFSI decomposition and consists mainly of sodium fluoride. Similarly, plating studies were used to understand the stability of different ionic liquids in contact with metallic sodium. It was found that the excellent capacity retention for the electrolyte consisting of NaFSI salt is related to the formation of a stable CEI and solid electrolyte interphase layers.
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