Effect of PAMAM Dendrimers on Interactions and Transport of LiTFSI and NaTFSI in Propylene Carbonate-Based Electrolytes

Polymer Electrolytes for Lithium-Ion Batteries Studied by NMR Techniques

This review is devoted to different types of novel polymer electrolytes for lithium power sources developed during the last decade. In the first part, the compositions and conductivity of various polymer electrolytes are considered. The second part contains NMR applications to the ion transport mechanism. Polymer electrolytes prevail over liquid electrolytes because of their exploitation safety and wider working temperature ranges. The gel electrolytes are mainly attractive. The systems based on polyethylene oxide, poly(vinylidene fluoride-co-hexafluoropropylene), poly(ethylene glycol) diacrylate, etc., modified by nanoparticle (TiO₂, SiO₂, etc.) additives and ionic liquids are considered in detail. NMR techniques such as high-resolution NMR, solid-state NMR, magic angle spinning (MAS) NMR, NMR relaxation, and pulsed-field gradient NMR applications are discussed. ¹H, ⁷Li, and ¹⁹F NMR methods applied to polymer electrolytes are considered. Primary attention is given to the revelation of the ion transport mechanism. A nanochannel structure, compositions of ion complexes, and mobilities of cations and anions studied by NMR, quantum-chemical, and ionic conductivity methods are discussed.

Selectively tuning ionic thermopower in all-solid-state flexible polymer composites for thermal sensing

There has been increasing interest in the emerging ionic thermoelectric materials with huge ionic thermopower. However, it's challenging to selectively tune the thermopower of all-solid-state polymer materials because the transportation of ions in all-solid-state polymers is much more complex than those of liquid-dominated gels. Herein, this work provides all-solid-state polymer materials with a wide tunable thermopower range (+20~-6 mV K-1), which is different from previously reported gels. Moreover, the mechanism of p-n conversion in all-solid-state ionic thermoelectric polymer material at the atomic scale was presented based on the analysis of Eastman entropy changes by molecular dynamics simulation, which provides a general strategy for tuning ionic thermopower and is beneficial to understand the fundamental mechanism of the p-n conversion. Furthermore, a self-powered ionic thermoelectric thermal sensor fabricated by the developed p- and n-type polymers demonstrated high sensitivity and durability, extending the application of ionic thermoelectric materials.

Reversible Magnesium Metal Anode Enabled by Cooperative Solvation/Surface Engineering in Carbonate Electrolytes

Magnesium metal anode holds great potentials toward future high energy and safe rechargeable magnesium battery technology due to its divalent redox and dendrite-free nature. Electrolytes based on Lewis acid chemistry enable the reversible Mg plating/stripping, while they fail to match most cathode materials toward high-voltage magnesium batteries. Herein, reversible Mg plating/stripping is achieved in conventional carbonate electrolytes enabled by the cooperative solvation/surface engineering. Strongly electronegative Cl from the MgCl₂ additive of electrolyte impairs the Mg…O = C interaction to reduce the Mg²⁺ desolvation barrier for accelerated redox kinetics, while the Mg²⁺-conducting polymer coating on the Mg surface ensures the facile Mg²⁺ migration and the effective isolation of electrolytes. As a result, reversible plating and stripping of Mg is demonstrated with a low overpotential of 0.7 V up to 2000 cycles. Moreover, benefitting from the wide electrochemical window of carbonate electrolytes, high-voltage (> 2.0 V) rechargeable magnesium batteries are achieved through assembling the electrode couple of Mg metal anode and Prussian blue-based cathodes. The present work provides a cooperative engineering strategy to promote the application of magnesium anode in carbonate electrolytes toward high energy rechargeable batteries.

Improvement of Electrochemical Stability Using the Eutectic Composition of a Ternary Molten Salt System for Highly Concentrated Electrolytes for Na-Ion Batteries

The increase in the concentration of electrolytes for secondary batteries has significant advantages in terms of physicochemical and electrochemical performance. This study aims to explore a highly concentrated electrolyte for Na-ion batteries using a ternary salt system. The eutectic composition of the Na[N(SO₂F)₂]-Na[N(SO₂F)(SO₂CF₃)]-Na[SO₃CF₃] ternary molten salt system increases solubility into an organic solvent, enabling the use of highly concentrated electrolytes for Na-ion batteries. The ternary salt system achieved concentrations of 5.0 m (m = mol kg^-1) with propylene carbonate (PC), 2.9 m with dimethoxyethane, 2.0 m with ethylene carbonate/dimethyl carbonate, and 3.9 m with ethylene carbonate/diethyl carbonate. The highly concentrated electrolyte of 5.0 m in PC suppressed Al corrosion and exhibited better oxidative stability. Stable electrochemical performance using hard carbon/NaCrO₂ in the full-cell configuration introduces a new strategy to explore highly concentrated electrolytes for secondary batteries.