Nanocomposites based on borate esters as improved lithium-ion electrolytes

Abstract

Borate esters with different lengths of ethyleneoxy units were investigated as electrolyte solvents for lithium salts such as lithium triflate, perchlorate, bis(trifluoromethanesulfonyl)imide, bis (pentafluoroethanesulfonyl)imide and bis(oxalato)borate. The ionic conductivity of the salt solutions was measured to be of the order of 10 À3 to 10 À4 S cm À1 at room temperature. Transference number measurements for the borate ester-lithium perchlorate system indicated roughly equal contributions of cations and anions to the total conductivity, while the borate ester-lithium bis(oxalato)borate showed predominant anionic conductivity. Nanocomposite electrolytes were prepared by heterogeneous doping of the borate esters with silica. Composites with 10 nm silica particles exhibited low-viscous electrolyte behavior with a clear but modest conductivity enhancement at very low volume fractions of silica and a depression of the conductivity value at higher volume fractions. In the case of fumed silica (7 nm) the nanocomposites had at a sufficiently high volume fraction and a jelly, transparent appearance with the favorable mechanical properties of a high-viscous semi-solid without noteworthy decrease in the Li ion conductivity. In particular the last material with its combination of favourable electrical, mechanical and optical properties, promises to be a viable candidate for various applications (Li-based batteries, solar cells).

Comparison of Li+‐ion conductivity in linear and crosslinked poly(ethylene oxide)

“…Thus, this sequence is not influenced by the molar mass between the junction points of the network electrolyte. A similar behavior has been reported by different authors for electrolyte systems with the same lithium salts, but they used different solvents, for example, ionic liquids or linear polymers …”

Robust Polyimide Nanofibrous Membrane with Bonding Microstructures Fabricated via Dipping Process for Lithium‐Ion Battery Separators

“…The slope of lines indicates a Warburg diffusion process, and the resistances of different separators are determined by the intersection of the spectrum line and x‐axis. The bulk resistances of the Celgard PP, PI nonwoven, PI‐2, and PI‐4 separators are 2.1, 0.7, 1.1, and 1.2 Ω, respectively. The ionic conductivities of the separators with liquid electrolyte are evaluated to be 0.59, 2.2, 1.43, and 1.31 mS cm −1 , respectively.…”

A single cation or anion dendrimer-based liquid electrolyte

“…The concept with limited success was later extended to liquids where dispersions of fine oxide particles in liquid electrolytes lead to modest enhancements in the effective conductivity of the liquid. 28 , 29 To the best of our knowledge the heterogeneous doping concept has not yet been utilized to transform the nature of ion transport in liquids. It is envisaged that the approach presented here is the first of its kind to be adopted in the realm of liquids.…”