3 research outputs found
Physicochemical Characterization of AlCl<sub>3</sub>–1-Ethyl-3-methylimidazolium Chloride Ionic Liquid Electrolytes for Aluminum Rechargeable Batteries
Al-ion
batteries technology is receiving growing attention thanks
to the high natural abundance of aluminum and to the high energy density
that can be obtained with a three-electron redox process. In this
work, the physicochemical properties of the room temperature ionic
liquid composed of aluminum chloride and 1-ethyl-3-methylimidazolium
chloride ([EMIm]ÂCl) were systematically investigated by varying the
molar ratio AlCl<sub>3</sub>/[EMIm]Cl in the range 1.1–1.7.
The combined use of multinuclear (<sup>27</sup>Al, <sup>13</sup>C, <sup>1</sup>H) NMR, electrochemical impedance spectroscopy, and thermal
analysis allowed us to shed light on the structure–properties
relationships of this complex system, also resolving some controversial
conclusions of previous literature. We showed that the 1.2 molar ratio
is the best compromise between high ionic conductivity and the use
of the highly toxic AlCl<sub>3</sub>. This electrolyte was tested
in a standard Al-ion cell and gave promising results even at very
high current densities (<i>i</i> > 200 mA g<sup>–1</sup>)
Ion Dynamics and Mechanical Properties of Sulfonated Polybenzimidazole Membranes for High-Temperature Proton Exchange Membrane Fuel Cells
Polybenzimidazole (PBI)-based membranes
are one of the systems
of choice for polymer electrolyte fuel cells. Monomer sulphonation
is one of the strategies suggested to improve proton transport in
these membranes. We report a NMR and dynamic mechanical study aiming
to investigate the effect of the sulphonation on the proton dynamics
and the mechanical properties of the membranes. The analyses of <sup>1</sup>H self-diffusion coefficients and <sup>1</sup>H and <sup>31</sup>P spectra versus temperature show that sulphonation causes the formation
of interchain cross-links, which involve phosphoric acid molecules
and the sulfonic groups. This, in turn, reduces the proton mobility
and, consequently, the ionic conductivity. The increase of the membrane
stiffness with sulphonation is confirmed by dynamic mechanical analysis
through the behavior of the storage modulus
Aqueous Processing of Na<sub>0.44</sub>MnO<sub>2</sub> Cathode Material for the Development of Greener Na-Ion Batteries
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 Na<sub>0.44</sub>MnO<sub>2</sub> (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 NaPF<sub>6</sub> 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<sup>–1</sup> 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<sup>–1</sup> with a Coulombic efficiency of 99.9%