Michele Vittadello

New solvent-free polymer electrolytes are proposed based on a linear perfluorinated copolymer synthesized by enzymatic methods. The system is biphasic and exhibits two distinct conductivity pathways for long-range Na⁺-cation migration.

Sodium‐containing ionic liquids are very promising candidates as ion‐conducting materials in alternative to electrolytes based on lithium chemistry. Here we investigate a series of seven ionic liquids with formula (EMImCl/(AlCl₃)_1.5)/(δ‐NaCl)_x (0≤x≤0.74). The salt is comprised of a disordered form of NaCl prepared by metalorganic synthesis, which assures faster dissolution in high concentration. The vibrational investigation carried out by FT‐IR spectroscopy in the medium IR region shed light on salt‐IL interactions. The ionic conductivity was investigated by Broadband Electric Spectroscopy. The direct current conductivity (σ_dc) profiles versus the reciprocal temperature exhibited a Vogel‐Tamman‐Fulcher behavior indicating the assistance of micro‐Brownian motions to ionic migration. The value of σ_dc at 25 °C for x=0.74 was found to be 1.2×10⁻² S cm⁻¹. Reversible deposition of Na and Al‐containing species take place with high Coulombic efficiency (up to 97 %) and a high Na⁺ cation transport number (up to 0.95). The understanding of ionic speciation was investigated in comparison with aqueous acid‐base systems exploring the benefits and limitations of such analogy. The role of a Grotthuss‐type mechanism facilitating the exchange of chlorides between acidic catenated chloroaluminate species in anionic domains of the ILs is considered.

Lithium-based electrolytes are, at least from a thermodynamic standpoint, the most suitable ion-transport materials for energy storage systems. However, lithium-based ionic conductors suffer from safety concerns, and the limited availability of lithium in the Earth’s crust is at the root of the need to consider alternative metal ions. Notably, sodium stands out as the sixth most-prevalent element; therefore, when considering mineral reserves, it as a very attractive candidate as an alternative to the status quo. Even if the specific energy and energy density of sodium are indeed inferior with respect to those of lithium, there is substantial economic appeal in promoting the use of the former metal in stationary energy storage applications. For these reasons, the promise of sodium is likely to extend to other commercial applications, including portable electronics, as well as hybrid and electric vehicles. Widely used organic liquid electrolytes, regardless of their chosen metal cation, are disadvantageous due to leakage, evaporation, and high flammability. Polymer electrolytes are acknowledged as the most effective candidates to overcome these obstacles and facilitate the advancement of next-generation energy storage applications. In this contribution, an in-depth and comprehensive review of sodium polymer electrolytes for primary and secondary batteries is proposed. The overarching goal was to gain insight into successful synthetic strategies and their implications for conduction parameters and conductivity mechanisms. The focus lies on solid, gel, and composite polymer electrolytes. Our hope is that the proposed discussion will be helpful to all operators in the field, whether in tackling fundamental research problems or resolving issues of practical significance.

We propose a physical mechanism of conformation-induced proton pumping in mitochondrial Complex I. The structural conformations of this protein are modeled as the motion of a piston having positive charges on both sides. A negatively charged electron attracts the piston, moving the other end away from the proton site, thereby reducing its energy and allowing a proton to populate the site. When the electron escapes, elastic forces assist the return of the piston, increasing proton site energy and facilitating proton transfer. We derive the Heisenberg equations of motion for electron and proton operators and rewrite them in the form of rate equations coupled to the phenomenological Langevin equation describing piston dynamics. This set of coupled equations is solved numerically. We show that proton pumping can be achieved within this model for a reasonable set of parameters. The dependencies of proton current on geometry, temperature, and other parameters are examined.