Li‐Ion Battery Electrolyte Formulated for Low‐Temperature Applications

Abstract

Low‐temperature (<0°C) applications of Li‐ion batteries have prompted the search for improved, high‐conductivity electrolytes. Because the performance of the carbonaceous anode is highly sensitive to changes in electrolyte composition, we focused our efforts on this electrode. Electrolytes containing LiAsF6,LiPF6,normalLiNfalse(SO2CF3)2 [lithium bis(trifluoromethanesulfonyl)imide], or LiIm, and normalLiCfalse(SO2CF3)3 [lithium tris(trifluoromethanesulfonyl)methide], or LiMe, in methyl formate (MF)‐ethylene carbonate (EC) solvent mixtures were tested in lithium‐graphite half‐cells. The graphite electrodes could be cycled at ambient temperature with high reversible capacity. The best supporting electrolyte was found to be LiAsF6 , and the presence of a high concentration of ethylene carbonate and up to 300 ppm H2O in the solution considerably increased the reversible capacity upon cycling. The conductivity values of a binary solvent mixture of methyl formate and ethylene carbonate containing LiAsF6 or LiMe were measured between −40°C and room temperature. Graphite electrodes cycled at −2°C in these electrolytes obtained reasonable reversible capacity, approaching 50%.

Variable temperature performance of intermetallic lithium-ion battery anode materials

“…At −30 • C, the electrode had little or no capacity at the rates used. The drop-off in capacity as a function of temperature and rate is in good agreement with previously reported results [7,33].…”

Nonaqueous Liquid Electrolytes for Lithium-Based Rechargeable Batteries

“…Therefore, the authors speculated that the SEI formed in the presence of low molecular weight esters appeared to be resistive and inadequately protective, whereas, in the presence of esters of higher molecular weight, the SEI could be formed with more desirable attributes. Combining the observations of Ein-Eli et al, 102 Smart et al, 461,462 and Herreyre et al, 406 it could be tentatively concluded that longer alkyl chains in the carboxylic acid section of the esters play a critical role in determining the cathodic stability of this component on a graphite anode. The tests in AA-size full lithium ion cells were only reported for EA-and MA-based quaternary electrolytes, and Figure 59 shows the discharging profiles of these cells at -40°C.…”

Temperature effect on electrochemical performances of Li-ion hybrid capacitors

“…As the performances of LIC cells at low temperature are mainly limited by carbon anode [25], further work on anode electrode remains to be undertaken, such as: (i) forming more effective conductive network to enhance the electric conductivity by the addition of carbon nanotube and/or graphene [35]; (ii) forming porous anode electrode to increase electrolyte uptake and reduce ionic transport path, facilitating lithium-ion diffusion from/to lithium intercalation sites by the adoption of porous graphite or nongraphite carbon [7,36,37]; (iii) using special electrolytes which are suitable for low-temperature operation to improve the lithium-ion concentration and mobility [24]; (iv) increasing lithium capacity of anode by raising the mass of active materials in anode or reducing the pre-lithiation degree. Nevertheless, the lithium plating and the growth of lithium dendrites in anode should be managed to be avoided during high-rate charging process at low temperatures.…”

“…It increases the risk of the lithium dendrite formation and growth on anode surface at high-rate charging processes, which can lead to the internal short-circuit failure of cells. The low cut-off potential of anode at low temperature is due to the decrease of the concentration of salt (LiPF 6 ) and the lithium-ion mobility [24] and the increase of the activation energy for lithium-ion diffusion and intercalation in carbon anode [25]. For LIC cells, the AC cathode is involved in the anion double-layer formation without obvious bulk redox.…”