Formulation of a New Type of Electrolytes for LiNi_1/3Co_1/3Mn_1/3O₂ Cathodes Working in an Ultra-Low Temperature Range

Abstract

A new type of electrolytes for low temperature operation of Li-ion batteries was formulated in this work. Instead of LiPF6, LiBF4 and LiODFB were used to form this new type of electrolytes, although LiPF6 is the mostly chosen solute in the state-of-the-art Li-ion electrolytes. It was found although a LiBF4-based electrolyte had a lower ionic conductivity than that of a LiODFB-based electrolyte, a LiODFB-based electrolyte demonstrated improved low temperature performance. In particular, at-30°C, a Li-ion cell with 1M LiODFB dissolved in a 1:2:5 (wt.) propylene carbonate (PC)/ethylene carbonate (EC)/ethyl methyl carbonate (EMC) mixed solvent delivered 86% of the capacity obtained at 20°C. Furthermore, the cells with a LiODFB-based electrolyte showed lower polarization at-30°C. The above results suggest that beside the ionic conductivity of an electrolyte as a limitation to the low temperature operation of Li-ion batteries, there was interface impedance having effect on it. Analysis of cell impedance revealed that reduced charge-transfer resistance by using LiODFB resulted in improved low temperature performance of Li-ion batteries.

2,3,4,5,6-Pentafluorophenyl Methanesulfonate as a Versatile Electrolyte Additive Matches LiNi0.5Co0.2Mn0.3O2/Graphite Batteries Working in a Wide-Temperature Range

“…15−18 It was demonstrated that some CEI and SEI layers not only improve the lithium ion diffusion and reduce the polarization and interface impedance of LIBs at low temperatures but also prevent the electrolyte decomposition and the reactions between the cathode materials and electrolyte at high temperatures. These typical additives include organic and inorganic functional molecules such as vinylene carbonate (VC), 19,20 propane sultone (PS), 21,22 butane sultone (BS), 23 vinylethylene carbonate (VEC), 24,25 lithium bis(oxalate)borate (LiBOB), 26 lithium oxalatodifluoro borate (LiODFB), 27 and lithium difluorophosphate (Li 2 PO 2 F 2 ). 28 Among them, PS, BS, and VEC generally act as high-temperature-type additives, while LiBOB, LiODFB, and Li 2 PO 2 F 2 are commonly used as low-temperature-type additives.…”

Solvate Structures and Computational/Spectroscopic Characterization of Lithium Difluoro(oxalato)borate (LiDFOB) Electrolytes

“…The difluoro(oxalato)borate (DFOB – ) anion, also known as oxalyldifluoroborate (ODFB – ), was first reported in a patent application filed in 1999 by Metallgesellschaft AG and in a publication in 2006 by the U.S. Army Research Laboratory (ARL) . The lithium salt with this anion (LiDFOB) has garnered significant interest in recent years for Li-ion battery electrolytes. − Little is known at present, however, about the molecular-level ionic interactions present once this salt is dissolved in the aprotic solvents used for electrolytes. Such knowledge is necessary to understand the origin of electrolyte properties as solvent–salt mixtures consist of a diverse range of solvate species. , …”

Formulation of Blended‐Lithium‐Salt Electrolytes for Lithium Batteries

“…[25][26][27][28][29][30][31] For the development of high-energy and high-performance LIBs (especially over a wide temperature range), blended-salt electrolytes based on LiBF 4 , which is favorable at low temperature (but shows poor compatibility with the graphite anode in alkyl carbonate solvents), and LiBOB or LiDFOB, which are favorable at high temperature (and also with respect to the SEI layer), have been proposed. [41,[74][75][76][77][78][79] Duncan et al reported that blended-salt electrolytes based on 1m LiBF 4 and 0.1m LiBOB with dinitriles (chain lengths of n = 4-8) as the only solvent or mixed with EC as a second solvent could not well sustain a high-voltage (5 V class) LiNi 0.5 Mn 1.5 O 4 /Li cell except when DMC was added as an additional solvent. [75] It was demonstrated that DMC had the ability to suppress the oxidative decomposition of the LiBF 4 salt at high voltage, by itself decomposing.…”