Density, Viscosity, Ionic Conductivity, and Self-Diffusion Coefficient of Organic Liquid Electrolytes: Part I. Propylene Carbonate + Li, Na, Mg and Ca Cation Salts

Abstract

To investigate physicochemical relationships between ionic radii, valence number and cationic metal species in electrolyte solutions, propylene carbonate with Li[N(SO 2 CF 3 ) 2 ], Na[N(SO 2 CF 3 ) 2 ], Mg[N(SO 2 CF 3 ) 2 ] 2 and Ca[N(SO 2 CF 3 ) 2 ] 2 were prepared. The temperature dependence of density, viscosity, ionic conductivity (AC impedance method) and self-diffusion coefficient (pulsed-gradient spin-echo nuclear magnetic resonance) was measured. The effects of cationic radii and cation valence number on the fluidity and transport properites (conductivity and self-diffusion coefficient) were analyzed. Research and development of lithium-ion batteries (LIBs) have focused on the efficient use of energy. Application fields of LIBs are spreading from portable commercial use (mobile phone and laptop PC) to large-scale energy systems (electric vehicle and accumulator for household use).1 Furthermore, the usages (utilities, needs, requirements and demands) of industrial-scaled electricity storage systems using LIBs are increasing for applications alongside renewable energy systems (photovoltaics and/or wind energy) and frequency regulation demands. However, resources and stock amounts of Li are limited. Another reactive cationic species, such as high Clarke number Na + (2.63, 6th) and divalent cations Mg 2+ (1.93, 8th) and Ca 2+ (3.39, 5th) have been reported as new cationic species for next-generation batteries (Li + : 0.0006, 27th). 2 The number of reports for battery operations using a Na (sodium) system is increasing, and they have focused on the research and development of electrode and electrolyte materials for, mainly, positive electrodes.3-5 Because of the differences of ionic radii between Li + (60 pm) and Na + (95 pm), understanding the effects of ionic radii on electrolyte properties is important. 6,7 In addition, comparison between monovalent cations and divalent cations (Mg 2+ : 65 pm, 8 Ca 2+ : 99 pm 9 ) is also important to understand the effects of valence number of cation on the electrolyte properties. In this study, an electrolyte solutions of propylene carbonate (PC) and N(SO 2 CF 3 ) 2 − ([TFSA] − ) anion-based metal (Li, Na, Mg and Ca) salts were prepared and evaluated by measuring their physicochemical properties. We investigate the dependence of static (density) and dynamic (macroscopic fluidity: viscosity, ionic mobility: ionic conductivity and microscopic ionic diffusivity: self-diffusion coefficient) properties of electrolytes on the cationic metal species of salts (ionic radii and valence number) and salt concentrations. We also analyze the intermolecular interactions of the cations with PC and [TFSA] − by ab initio molecular orbital calculations. Using the mearurements of static and dynamic properties and analysis of interactions, the expectations of innovative next-generation battery systems are discussed. ExperimentalMaterials.-PC (Kishida Chemical, battery grade) and metal cation salts (Table I) were used as the solvent and dissolved salts for electrolyte solutions, respectively...

In‐Situ Intermolecular Interaction in Composite Polymer Electrolyte for Ultralong Life Quasi‐Solid‐State Lithium Metal Batteries

“…Surprisingly, an optimum ionic conductivity of 1.43×10 −3 S cm −1 at 25 °C was attained for the composite electrolyte, registering the highest conductivity for PEO‐based lithium solid electrolyte ever reported. This value is roughly equal to the ionic conductivity of commercial liquid electrolyte (≈10 −3 S cm −1 at ambient temperature) [27] . The LiFePO 4 /P(EO) 15 LiTFSI‐0.2LLZTO‐1.1EC (PLLE‐3)/Li solid batteries exhibit excellent cycling stability and rate capacity, superior to all the bulk composite polymer electrolyte based lithium batteries that have been reported in the literature up to date.…”

“…This value is roughly equal to the ionic conductivity of commercial liquid electrolyte ( % 10 À3 Scm À1 at ambient temperature). [27] The LiFePO 4 /P(EO) 15 LiTFSI-0.2LLZTO-1.1EC (PLLE-3)/Li solid batteries exhibit excellent cycling stability and rate capacity,s uperior to all the bulk composite polymer electrolyte based lithium batteries that have been reported in the literature up to date.The synergistic effect of the components in SCE was elucidated in Scheme 1. Thec ontaminating LiOH/Li 2 CO 3 around LLZTO particles serves as initiator for the formation of ether oligomers from ring opening reaction of ethylene carbonate,w hich further hydrogen bonded with PEO chains to construct an PEO/LLZTOi nterface with improved compatibility.T he oligomers further act as plasticizer to reduce the crystallinity of PEO matrix and maintain its amorphous state through hydrogen bonding.I nt his way, the modified LLZTO/PEO interface guarantees ar apid Li + conduction tunnel and enables regulated Li + deposition at lithium anode with the assistance of high Li + flux in amorphous PEO.T he outcomes offer new insights into the functional ingredients in designing novel composite electro-lytes with excellent performance for next-generation quasisolid-state batteries.…”

Operational Strategies to Improve the Performance and Long‐Term Cyclability of Intermediate Temperature Sodium‐Sulfur Batteries

“…The formation of larger aggregates increases the molar conductivity to a maximum during an initial increase in concentration. Augmenting the concentration to 2.5 M strengthens the ionic interaction of the aggregates and reduces the mobility of the ionic current‐carriers [49] . Macroscopically visualized, a rise in the viscosity of the catholyte enacts it to behave like an ionic liquid [48] .…”

“…Augmenting the concentration to 2.5 M strengthens the ionic interaction of the aggregates and reduces the mobility of the ionic currentcarriers. [49] Macroscopically visualized, a rise in the viscosity of the catholyte enacts it to behave like an ionic liquid. [48] The above finding benchmarks the catholyte concentration to 1 M, and within this limit, the conductance doesn't vary significantly for the measured temperatures (125 and 135°C).…”

Efficient Recovery of Silver from Crystalline Silicon Solar Cells by Controlling the Viscosity of Electrolyte Solvent in an Electrochemical Process

“…Although Ag has excellent solubility in MSA, the electrochemical efficiency of MSA is not expected to be good, owing to its high viscosity, because the Ag ions have lower mobility in a high-viscosity electrolyte [18], which is also related to diffusion [19,20]. Therefore, CV was performed to confirm the diffusion coefficient according to the amount of water added to MSA and the CV curves are shown in Figure 1.…”