Abstract
Improving the fast charging performance of lithium ion batteries (LIBs) has the promise to increase the widespread adoption of electric vehicles (EVs). Electrolyte development plays an important role in enabling fast charging. In this study, fast charging performance of LIBs is studied with different electrolytes of 1.2 M LiPF6 in Ethylene Carbonate (EC)/Ethyl Methyl Carbonate (EMC)/co-solvents at 30/50/20 wt%. The co-solvents are methyl acetate (MA), ethyl acetate (EA), ethyl formate (EF), dimethyl carbonate (DMC) and EMC. Long term cycling performance under fast charging shows different capacity retention behaviors for different co-solvents. The structural changes in the electrode material are studied by X-ray absorption spectroscopy (XAS) and X-ray diffraction (XRD). The molarity changes in electrolyte is investigated by inductively coupled plasma-optical emission spectroscopy (ICP-OES). The electrode/electrolyte interfaces before and after fast charging are analyzed by X-ray photoemission spectroscopy (XPS). The characterization results are in good agreement with the long-term cycling performance. DMC shows the highest fast-charging capability among the five studied co-solvents due to its increased conductivity, improved electrode/electrolyte interface and stable electrode structural integrity.
| Original language | English |
|---|---|
| Article number | 136453 |
| Journal | Electrochimica Acta |
| Volume | 353 |
| DOIs | |
| State | Published - Sep 1 2020 |
Funding
This research at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy ( DOE ) under contract DE-AC05-00OR22725 , was sponsored by the Office of Energy Efficiency and Renewable Energy ( EERE ) Vehicle Technologies Office ( VTO ) (Technology Manager: Brian Cunningham). XRD was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357 . The XPS study was performed at the Surface Analysis Laboratory in Department of Chemistry at Virginia Tech, which is supported by the National Science Foundation under Grant No. CHE-1531834. We acknowledge James Kwon in assistance with the Karl Fisher Titration test. This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan ( http://energy.gov/downloads/doe-public-access-plan ). The surface chemistry on both cathodes and anodes was studied by XPS after formation and after 200 fast-charging cycles. Fig. 8 and Fig. 9 show the detailed analysis of F 1s, C 1s, O 1s and P 2p of solid electrolyte interphase (SEI) on graphite electrodes and cathode electrolyte interphase (CEI) on NMC622 electrodes. It is well known that the SEI and CEI consist mainly of organic components including (CH2>OCO2Li)2 (lithium ethylene decarbonate, LEDC), other organic carbonates (R2CO3), polyethylene glycol (PEO) oligomer, etc., and inorganic compounds such as Li2CO3, LiF, Li2O, LiPFxOy and LixPFy [40?43]. The detailed peak assignments for the SEI/CEI layers are summarized in Table S2 and S3 (supporting information).This manuscript has been authored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/downloads/doe-public-access-plan).This research at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) under contract DE-AC05-00OR22725, was sponsored by the Office of Energy Efficiency and Renewable Energy (EERE) Vehicle Technologies Office (VTO) (Technology Manager: Brian Cunningham). XRD was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. The XPS study was performed at the Surface Analysis Laboratory in Department of Chemistry at Virginia Tech, which is supported by the National Science Foundation under Grant No. CHE-1531834. We acknowledge James Kwon in assistance with the Karl Fisher Titration test.
| Funders | Funder number |
|---|---|
| DOE Office of Science | |
| DOE Public Access Plan | |
| United States Government | |
| National Science Foundation | CHE-1531834 |
| U.S. Department of Energy | DE-AC05-00OR22725 |
| Battelle | |
| Office of Science | |
| Office of Energy Efficiency and Renewable Energy | |
| Argonne National Laboratory | DE-AC02-06CH11357 |
| Oak Ridge National Laboratory | |
| UT-Battelle |
Keywords
- Electrode/electrolyte interphase
- Electrolyte
- Fast charging
- Li-ion cells
