RESUMO
Ionic liquids (ILs) are considered as appealing alternative electrolytes for application in rechargeable batteries, including next-generation sodium-ion batteries, because of their safe and eco-friendly nature, resulting from their extremely low volatility. In this work, two groups of advanced pyrrolidinium-based IL electrolytes are concerned, made by mixing sodium bis(fluorosulfonyl)imide (NaFSI) or sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) salts salts with N-methyl- N-propylpyrrolidinium bis(fluorosulfonyl)imide (Pyr13FSI), N-butyl- N-methylpyrrolidinium bis(fluorosulfonyl)imide (Pyr14FSI), and N-butyl- N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr13FSI). The characterization of eight different electrolytes, including single anion electrolytes and binary anion mixtures, in terms of thermal properties, density, viscosity, and conductivity, as well as electrochemical stability window and cycling performance in room-temperature sodium cells, is reported here. Among all of the blends, those containing Pyr14FSI outperform the others in terms of cell performance enabling the layered P2-Na0.6Ni0.22Al0.11Mn0.66O2 cathode to deliver about 140 mAh g-1 for more than 200 cycles.
RESUMO
The implementation of aqueous electrode processing of cathode materials is a key for the development of greener Na-ion batteries. Herein, the development and optimization of the aqueous electrode processing for the ecofriendly Na0.44MnO2 (NMO) cathode material, employing carboxymethyl cellulose (CMC) as binder, are reported for the first time. The characterization of such an electrode reveals that the performances are strongly affected by the employed electrolyte solution, especially, the sodium salt and the use of electrolyte's additives. In particular, the best results are obtained using the 1 M solution of NaPF6 in EC/DEC (ethylene carbonate/diethyl carbonate) 3:7 (v/v) + 2 wt % FEC (fluoroethylene carbonate). With this electrolyte, the outstanding capacity of 99.7 mA h g-1 is delivered by the CMC-NMO cathode after 800 cycles at a 1C charge/discharge rate. On the basis of this excellent long-term performance, a full sodium cell, composed of a CMC-based NMO cathode and hard carbon from biowaste (corn cob), has been assembled and tested. The cell delivers excellent performances in terms of specific capacity, capacity retention, and long-term cycling stability. After 75 cycles at a C/5 rate, the capacity of the NMO in the full-cell approaches 109 mA h g-1 with a Coulombic efficiency of 99.9%.
RESUMO
We report the first proof of concept for a non-aqueous semi-solid flow battery (SSFB) based on Na-ion chemistry using P2-type NaxNi0.22Co0.11Mn0.66O2 and NaTi2(PO4)3 as positive and negative electrodes, respectively. This concept opens the door for developing a new low-cost type of non-aqueous semi-solid flow batteries based on the rich chemistry of Na-ion intercalating compounds.