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Title: Wide-Temperature Electrolytes for Lithium-Ion Batteries

Abstract

Formulating electrolytes with solvents of low freezing points and high dielectric constants is a direct approach to extend the service temperature range of lithium (Li)-ion batteries (LIBs), for which propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl butyrate (MB) are excellent candidates. In this work, we report such low temperature electrolyte formulations by optimizing the content of ethylene carbonate (EC) in the EC-PC-EMC ternary solvent system with LiPF6 salt and CsPF6 additive. An extended service temperature range from 40°C to 60°C was obtained in LIBs with lithium nickel cobalt aluminum mixed oxide (LiNi0.80Co0.15Al0.05O2, NCA) as cathode and graphite as anode. The discharge capacities at low temperatures and the cycle life at room and elevated temperatures were systematically investigated in association with the ionic conductivity and phase transition behaviors. The most promising electrolyte formulation was identified as 1.0 M LiPF6 in EC-PC-EMC (1:1:8 by wt.) with 0.05 M CsPF6, which was demonstrated in both coin cells of graphite||NCA and 1 Ah pouch cells of graphite||LiNi1/3Mn1/3Co1/3O2. This optimized electrolyte enables excellent wide-temperature performances, as evidenced by the 68% capacity retention at 40C and C/5 rate, and nearly identical stable cycle life at room and elevated temperatures up to 60C.

Authors:
; ; ORCiD logo; ORCiD logo; ; ; ORCiD logo; ; ORCiD logo; ORCiD logo
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE Office of Energy Efficiency and Renewable Energy (EERE), Vehicle Technologies Office (EE-3V)
OSTI Identifier:
1363998
Report Number(s):
PNNL-SA-124731
Journal ID: ISSN 1944-8244; 49321
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: ACS Applied Materials and Interfaces; Journal Volume: 9; Journal Issue: 22
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE; wide temperature performance; low temperature discharge; electrolyte; cesium cation; Environmental Molecular Sciences Laboratory

Citation Formats

Li, Qiuyan, Jiao, Shuhong, Luo, Langli, Ding, Michael S., Zheng, Jianming, Cartmell, Samuel S., Wang, Chong-Min, Xu, Kang, Zhang, Ji-Guang, and Xu, Wu. Wide-Temperature Electrolytes for Lithium-Ion Batteries. United States: N. p., 2017. Web. doi:10.1021/acsami.7b04099.
Li, Qiuyan, Jiao, Shuhong, Luo, Langli, Ding, Michael S., Zheng, Jianming, Cartmell, Samuel S., Wang, Chong-Min, Xu, Kang, Zhang, Ji-Guang, & Xu, Wu. Wide-Temperature Electrolytes for Lithium-Ion Batteries. United States. doi:10.1021/acsami.7b04099.
Li, Qiuyan, Jiao, Shuhong, Luo, Langli, Ding, Michael S., Zheng, Jianming, Cartmell, Samuel S., Wang, Chong-Min, Xu, Kang, Zhang, Ji-Guang, and Xu, Wu. 2017. "Wide-Temperature Electrolytes for Lithium-Ion Batteries". United States. doi:10.1021/acsami.7b04099.
@article{osti_1363998,
title = {Wide-Temperature Electrolytes for Lithium-Ion Batteries},
author = {Li, Qiuyan and Jiao, Shuhong and Luo, Langli and Ding, Michael S. and Zheng, Jianming and Cartmell, Samuel S. and Wang, Chong-Min and Xu, Kang and Zhang, Ji-Guang and Xu, Wu},
abstractNote = {Formulating electrolytes with solvents of low freezing points and high dielectric constants is a direct approach to extend the service temperature range of lithium (Li)-ion batteries (LIBs), for which propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl butyrate (MB) are excellent candidates. In this work, we report such low temperature electrolyte formulations by optimizing the content of ethylene carbonate (EC) in the EC-PC-EMC ternary solvent system with LiPF6 salt and CsPF6 additive. An extended service temperature range from 40°C to 60°C was obtained in LIBs with lithium nickel cobalt aluminum mixed oxide (LiNi0.80Co0.15Al0.05O2, NCA) as cathode and graphite as anode. The discharge capacities at low temperatures and the cycle life at room and elevated temperatures were systematically investigated in association with the ionic conductivity and phase transition behaviors. The most promising electrolyte formulation was identified as 1.0 M LiPF6 in EC-PC-EMC (1:1:8 by wt.) with 0.05 M CsPF6, which was demonstrated in both coin cells of graphite||NCA and 1 Ah pouch cells of graphite||LiNi1/3Mn1/3Co1/3O2. This optimized electrolyte enables excellent wide-temperature performances, as evidenced by the 68% capacity retention at 40C and C/5 rate, and nearly identical stable cycle life at room and elevated temperatures up to 60C.},
doi = {10.1021/acsami.7b04099},
journal = {ACS Applied Materials and Interfaces},
number = 22,
volume = 9,
place = {United States},
year = 2017,
month = 5
}
  • The low-temperature performance of lithium-ion cells is mainly limited by the electrolyte solution, which not only determines the ionic mobility between electrodes but also strongly affects the nature of surface films formed on the carbonaceous anode. The surface films provide kinetic stability to the electrode (toward electrolyte) and permit charge (electron) transfer across them, which in turn determine the cycle life and rate capability of lithium-ion cells. Aiming at enhancing low-temperature cell performance, the authors have studied electrolyte solutions based on different ratios of alkyl carbonate solvent mixtures, i.e., ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC), inmore » terms of electrolyte conductivity, film resistance, film stability, and kinetics of lithium intercalation and deintercalation, at various temperatures. Electrolytes based on the ternary mixtures of EC, DEC, and DMC emerged as preferred combination compared to the binary analogues both in terms of conductivity and surface film characteristics, especially at low temperatures. These studies are further corroborated in sealed AA cells, which showed a synergistic effect of high durability from the DMC-based solutions and improved low-temperature performance from the DEC-based electrolytes.« less
  • Tetrahydrofuran (THF): 2-methyl-tetrahydrofuran (2Me-THF)/LiAsF/sub 6/ mixed solutions, despite their lower conductivity, have allowed significantly better low temperature performance in Li/TiS/sub 2/ cells than have THF/LiAsF/sub 6/, /sup 13/C NMR data suggest that this may be related to the structurally disordered Li/sup +/-solvates that exist in the mixed ether solutions. High cycling efficiencies for the Li electrode in THF:2Me-THF/LiAsF/sub 6/ solutions have been achieved by the use of 2Me-F as an additive. A 5 Ah capacity Li/TiS/sub 2/ cell has been cycled more than 100 times at 100, depth-of-discharge, with the cell capacity remaining at over 3 Ah at the 100thmore » cycle.« less
  • Carbonaceous anode materials in lithium-ion rechargeable cells exhibit irreversible capacity, mainly due to reaction of lithium during the formation of passive surface films. The stability and kinetics of lithium intercalation into the carbon anodes are determined by these films. The nature, thickness, and morphology of these films are in turn affected by the electrolyte components, primarily the solvent constituents. In this work, the films formed on graphite anodes in low-temperature electrolytes, i.e., solutions with different mixtures of alkyl carbonates and low-viscosity solvent additives, are examined using electrochemical impedance spectroscopy (EIS) and solid-state {sup 7}Li nuclear magnetic resonance techniques. In addition,more » other ex situ studies such as X-ray diffraction, transmission electron microscopy, and electron energy loss spectroscopy were carried out on the graphite anodes to understand their microstructures.« less
  • Rechargeable lithium (Li) metal batteries with conventional LiPF6-carbonate electrolytes have been reported to fail quickly at charging current densities of about 1.0 mA cm-2 and above. In this work, we demonstrate the rapid charging capability of the Li||LiNi0.8Co0.15Al0.05O2 (NCA) cells enabled by a dual-salt electrolyte of LiTFSI-LiBOB in a carbonate solvent mixture. It is found that the thickness of solid electrolyte interphase (SEI) layer on Li metal anode largely increases with increasing charging current density. However, the cells using the LiTFSI-LiBOB dual-salt electrolyte significantly outperforms those using the LiPF6 electrolyte at high charging current densities. At the charging current densitymore » of 1.50 mA cm-2, the Li||NCA cells with the dual-salt electrolyte can still deliver a discharge capacity of 131 mAh g-1 and a capacity retention of 80% after 100 cycles, while those with the LiPF6 electrolyte start to show fast capacity fading after the 30th cycle and only exhibit a low capacity of 25 mAh g-1 and a low retention of 15% after 100 cycles. The reasons for the good chargeability and cycling stability of the cells using LiTFSI-LiBOB dual-salt electrolyte can be attributed to the good film-formation ability of the electrolyte on lithium metal anode and the highly conductive nature of the sulfur-rich interphase layer.« less