A Multi-Functional Electrolyte for Lithium-Ion Batteries

Abstract

A MULTI-FUNCTIONAL ELECTROLYTE FOR LITHIUM-ION BATTERIESThermal management of lithium-ion batteries (LIBs) is paramount for multi-cell packs, such as those found in electric vehicles, to ensure safe and sustainable operation. Thermal management systems (TMSs) maintain cell temperatures well below those associated with capacity fade and thermal runaway to ensure safe operation and prolong the useful life of the pack.Current TMSs employ single-phase liquid cooling to the exterior surfaces of every cell, decreasing the volumetric and gravimetric energy density of the pack. In the present study, a novel, internal TMS that utilizes a multi-functional electrolyte (MFE) is investigated, which contains a volatile co-solvent that boils upon heat absorption in small channels in the positive electrode of the cell.

Synergistic Effect of Partially Fluorinated Ether and Fluoroethylene Carbonate for High-Voltage Lithium-Ion Batteries with Rapid Chargeability and Dischargeability

“…Spinel-type LiNi x Mn 2– x O 4 ( x = 0.4–0.6) has recently gained recognition as a promising cathode material for high-energy-density LIBs, largely on the basis of its high operating potential of 4.7 V vs Li/Li + , its low cost, and the high Li + -ion diffusivity within the three-dimensional channels of the spinel structure. − However, high-voltage LiNi x Mn 2– x O 4 suffers from the severe oxidative decomposition of conventional carbonate-based electrolytes, limiting its window of electrochemical stability. − The oxidative decomposition of the solvents in the electrolyte can be alleviated by decreasing their highest occupied molecular orbital (HOMO) energy levels. In this regard, fluorinated organic solvents have been proposed as promising high-voltage solvents owing to their low HOMO energy levels compared to those of nonfluorinated solvents. − In addition, partially fluorinated ether (PFE) solvents such as nonafluorobutyl methyl ether and 1,1,1,3,3,3,-hexafluoroisopropyl methyl ether can be used to reduce the flammability of organic liquid electrolytes because they have no flash point. − The rate capability of batteries is highly affected by the electrode density (thickness and porosity), charge transport at the electrode–electrolyte interface, and electronic conduction at the electrode–current collector interface. , The use of partially fluorinated ether solvents with low viscosities and high resistance to oxidation is expected to improve the wettability of the electrolyte toward the high-density electrode and the electrochemical performance of high-voltage batteries at high rates.…”