Improved Compatibility of α‐NaMnO2 Cathodes at the Interface with Ionic Liquid Electrolytes

Abstract

AbstractThe behaviour and compatibility of monoclinic sodium manganite, α‐NaMnO2, cathodes at the interface with electrolytes based on the 1‐ethyl‐3‐methylimidazolium bis(fluorosulfonyl)imide (EMIFSI) and N‐trimethyl‐N‐butylammonium bis(fluorosulfonyl)imide (N1114FSI) ionic liquids is presented and discussed. The Na+ insertion process was analysed through cyclic voltammetry tests combined with impedance spectroscopy measurements and the cell performance was tested by charge‐discharge cycles. XPS and FIB‐SEM measurements allowed analysis of the surface composition and the morphology of post‐mortem cathodes. Overall, the α‐NaMnO2 cathode showed high reversibility in N1114FSI‐based electrolyte, delivering 60 % of the initial capacity after 1200 cycles in conjunction with a Coulombic efficiency above 99 %. To our knowledge, these very promising results are the best result obtained till now for monolithic α‐NaMnO2 cathodes, are ascribable to the formation of a stable passive layer onto the electrode surface, as confirmed by spectroscopic analysis.