Issue 3, 2018

Stability enhancing ionic liquid hybrid electrolyte for NVP@C cathode based sodium batteries

Abstract

Cost-efficient, high-voltage, stable sodium-based cathodes are needed to develop commercial-scale sodium batteries. In this work, a Na3V2(PO4)3/carbon (NVP@C) composite sodium cathode material is synthesized by a novel, facile, two-step, solid state method. This material delivered a discharge capacity of 115 mA h g−1 at 0.5C rate with a conventional organic electrolyte. Improvements in stable cycling were found when NVP@C was paired with a “hybrid” electrolyte comprising a [50 : 50] v/v mixture of 1 M sodium bis(fluorosulfonyl)amide (NaFSI) in an organic electrolyte and an ionic liquid, N-methyl-N-propyl pyrrolidinium bis(trifluoromethanesulfonyl)amide (C3mpyrTFSI). Sodium batteries based on the NVP@C cathode retained 95% of their initial capacity after 100 cycles at 0.5C rate. We show that the hybrid electrolyte enhanced the electrochemical performance of the NVP@C cathode material by forming a stable SEI (solid-electrolyte interphase) layer on the surface. Electron microscopy and X-ray photoelectron spectroscopy were used to study the SEI layers on electrodes that had been subjected to 100 cycles with hybrid or conventional organic electrolytes. The hybrid electrolyte produced a less resistive, highly Na+ ion permeable SEI layer, explaining its superior sodium battery performance, compared to that found with the conventional organic electrolyte.

Graphical abstract: Stability enhancing ionic liquid hybrid electrolyte for NVP@C cathode based sodium batteries

Supplementary files

Article information

Article type
Paper
Submitted
06 Nov. 2017
Accepted
04 Janv. 2018
First published
10 Janv. 2018

Sustainable Energy Fuels, 2018,2, 566-576

Stability enhancing ionic liquid hybrid electrolyte for NVP@C cathode based sodium batteries

C. V. Manohar, A. Raj K, M. Kar, M. Forsyth, D. R. MacFarlane and S. Mitra, Sustainable Energy Fuels, 2018, 2, 566 DOI: 10.1039/C7SE00537G

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