Physicochemical Characterization of AlCl₃–1-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]­Cl) were systematically investigated by varying the molar ratio AlCl₃/[EMIm]Cl in the range 1.1–1.7. The combined use of multinuclear (²⁷Al, ¹³C, ¹H) 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 AlCl₃. 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^–1)

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 ¹H self-diffusion coefficients and ¹H and ³¹P 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_0.44MnO₂ 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_0.44MnO₂ (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%