Sulfolane‐Based Ethylene Carbonate‐Free Electrolytes for LiNi_0.6Mn_0.2Co_0.2O₂−Li₄Ti₅O₁₂ Batteries

Abstract

Most electrolytes in today's lithium-ion batteries contain a large proportion of ethylene carbonate (EC) mixed with other alkyl carbonate-based solvents. EC has, however, been shown to be unstable at the high potentials at which several novel cathode materials are electrochemically active. Here, different mixtures of sulfolane and DMC are investigated in this context. The electrochemical stability is explored in addition to galvanostatic cycling of LiNi 0.6 Mn 0.2 Co 0.2 O 2 -Li 4 Ti 5 O 12 (NMC-LTO) cells. The measurement of the ionic conductivity showed that mixing 25 % sulfolane into DMC improved the electrolyte properties as compared to pure DMC, making the conductivity similar to EC: DEC electrolytes and therefore fully functional. Moreover, the addition of sulfolane slightly enhanced the capacity retention, likely caused by formation of thinner and more stable surface layers on the LTO electrodes as determined by X-ray photoelectron spectroscopy (XPS). The cycling performance is especially improved for sulfolane-based electrolytes during cycling at sub-zero temperatures.[a] Dr.

An Attempt to Formulate Non‐Carbonate Electrolytes for Sodium‐Ion Batteries

“…Yet, the high melting point means that TMS, just like ethylene carbonate is not practical as a single solvent. However, the results from our initial trials, and previous works by other authors, attest that TMS is a promising electrolyte solvent [53–56] . In our study, the cells with additive‐free TMS displayed an ICE of 64–67 %, with energy efficiencies close to 90 % when cycling at 30 mA g −1 .…”

“…However, the results from our initial trials, and previous works by other authors, attest that TMS is a promising electrolyte solvent. [53][54][55][56] In our study, the cells with additive-free TMS displayed an ICE of 64-67 %, with energy efficiencies close to 90 % when cycling at 30 mA g À 1 . The most common measure to rectify the high melting point of TMS is to use it in combination with co-solvents.…”

Ti‐Based Surface Integrated Layer and Bulk Doping for Stable Voltage and Long Life of Li‐Rich Layered Cathodes

“…This indicates that cathode‐electrolyte interfacial reactions for PM sample is more serious than that for Ti‐treated samples. [ 26 ] Therefore, O 1s data further demonstrate that the surface Ti‐based integrated layer effectively mitigates interfacial reactions during cycling.…”

Understanding the Electrochemical and Interfacial Behavior of Sulfolane based Electrolyte in LiNi0.5Mn1.5O4‐Graphite Full‐Cells

“…[9,10] Hence, the use of EC-free electrolytes has appeared as a strategy to formulate electrolytes for high-voltage cathodes. [11] In this context, studies have been reported on potential electrolytes that are more stable at higher voltages. Electrolytes with sulfones, [12] nitriles, [13] ionic liquids, [14] fluorinated carbonates [15] have been explored with/without co-solvents to decrease their viscosities.…”

“…[19][20][21][22][23][24] Sulfolane exhibits a high boiling point of 287 °C, a flash point of 165 °C and a dielectric constant of > 40, primarily due to the oxygen in the sulfone group which is the coordinating motif to the lithium ion, and which triggers dissolution of lithium salts. [8,11,18] With respect to the conducting salt, lithium bis(fluorosulfonyl)imide (LiFSI) has a thermal stability of 200 °C and high solubility in organic solvents. [25] Since fluorine in LiFSI has a lower tendency to form hydrogen fluoride compared to that in the conventional electrolytes containing lithium hexafluorophosphate (LiPF 6 ), the transition metal dissolution occurring in LNMO at higher potentials can be decreased.…”