Boroxine ring compounds as dissociation enhancers in gel polyelectrolytes

Electrochemical Characterization of Single Lithium-Ion Conducting Polymer Electrolytes Based on sp3 Boron and Poly(ethylene glycol) Bridges

A novel series of single lithium-ion conducting polymer electrolytes (SLICPE) based on sp³ boron and poly(ethylene glycol) (PEG) bridges is presented, in the context of the development of a new generation of batteries, with the aim to overcome the problems related to concentration overpotential and low ion transport numbers in conventional solid polymer electrolytes (SPE). The phase separation generated by the physical mixture of SPE with plasticizers such as poly(ethylene oxide) is still a serious problem. In this work, the use of PEG with different chain lengths, for the polycondensation reaction with LiB(OCH₃)₄, to synthesize SLICPE allows preventing phase separation while tuning the predominant conduction mechanism, and thus the electrical properties, especially the lithium-ion transference number. The ionic transport is promoted by chain mobility as the chain length is increased. SLICPE with the best ionic conductivity values (4.95 ± 0.05) × 10^-6 S cm^-1 was the one synthesized from poly(ethylene glycol) with an average M_N of 400 (BEG8), having an O/Li⁺ ratio of 20. The lithium transference number ( t_Li⁺) and electrochemical stability window of SLICPE membranes at 25 °C decreased as the PEG bridge length between sp³ boron atoms increased from 0.97 to 0.88 and 5.4 to 4.2 V vs Li⁰/Li⁺, respectively, for SLICPE synthesized from PEG with an average M_N of 50-400 (BEG1 to BEG8).

Polymer Electrolytes Based on Borane/Poly(ethylene glycol) Methyl Ether for Lithium Batteries

This work presents a different approach to preparing polymer electrolytes having borate ester groups for lithium ion batteries. The polymers were synthesized by reaction between poly(ethylene glycol) methyl ether (PEGME) and BH3-THF complex. Molecular weight of PEGMEs was changed with different chain lengths. Then the polymer electrolytes comprising boron were prepared by doping of the matrices with CF3SO3Li at various molar ratios with respect to EO to Li and they are abbreviated as PEGMEX-B-Y. The identification of the PEGME-borate esters was carried out by FTIR and 1H NMR spectroscopy. Thermal properties of these electrolytes were investigated via thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The ionic conductivity of these novel polymer electrolytes was studied by dielectric-impedance spectroscopy. Lithium ion conductivity of these electrolytes was changed by the length of PEGME as well as the doping ratios. They exhibit approximate conductivities of 10−4 S·cm−1 at 30°C and 10−3 S·cm−1 at 100°C.