TY - JOUR
T1 - Improving Cell Resistance and Cycle Life with Solvate-Coated Thiophosphate Solid Electrolytes in Lithium Batteries
AU - Philip, Maria A.
AU - Sullivan, Patrick T.
AU - Zhang, Ruixian
AU - Wooley, Griffin A.
AU - Kohn, Stephanie A.
AU - Gewirth, Andrew A.
N1 - Funding Information:
This work was supported as part of the Center for Electrochemical Energy Science, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences. This research was carried out in part in the Frederick Seitz Materials Research Laboratory Central Research Facilities, University of Illinois. We would like to thank Minjeong Shin and Kenneth Madsen of the Department of Chemistry at the University of Illinois at Urbana-Champaign for valuable input. We thank Jaroslaw Syzdek of BioLogic Science Instruments for helpful discussions on EIS.
Publisher Copyright:
© 2018 American Chemical Society.
PY - 2019/1/16
Y1 - 2019/1/16
N2 - Solid electrolytes (SEs) have become a practical option for lithium ion and lithium metal batteries because of their improved safety over commercially available ionic liquids. The most promising of the SEs are the thiophosphates, whose excellent ionic conductivities at room temperature are comparable to those of commercially utilized ionic liquids. Hybrid solid-liquid electrolytes exhibit higher ionic conductivities than their bare SE counterparts because of decreased grain boundary resistance, enhanced interfacial contact with electrodes, and decreased degradation at the interface. In this study, we add lithium bis(trifluoromethane sulfonyl)imide and a highly fluorinated ether solvate electrolyte to the surface of Li 7 P 3 S 11 (LPS) and Li 10 GeP 2 S 12 (LGPS) pellets and evaluate their overall cell resistance in Li-Li symmetric cells relative to their bare Li/SE/Li counterparts. Time-resolved electrochemical impedance spectroscopy shows an order of magnitude lower cell resistance for LGPS-solvate than for bare LGPS. In contrast, the LPS-solvate system exhibits a higher cell resistance than bare LPS. Scanning electron microscopy and energy dispersive X-ray spectroscopy show that LGPS allows for the total permeation of the solvate into the bulk SE. Although LPS has smaller grain sizes and higher porosity, it has a higher solubility in 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE), which results in an LPS-TTE interlayer on the surface of the pellet, thereby increasing overall cell resistance. Cyclic voltammetry of the bare and hybrid SE cells shows an order of magnitude higher current density for the LGPS-solvate cell over the bare LGPS. Bare LPS shorts after two cycles, whereas the LPS-solvate cell does not short within the timeframe of the experiment (100 cycles). This study suggests that solvates can be used to improve the cell resistance and current density of SEs by altering the grain boundary structures and the interphase between electrode and electrolyte.
AB - Solid electrolytes (SEs) have become a practical option for lithium ion and lithium metal batteries because of their improved safety over commercially available ionic liquids. The most promising of the SEs are the thiophosphates, whose excellent ionic conductivities at room temperature are comparable to those of commercially utilized ionic liquids. Hybrid solid-liquid electrolytes exhibit higher ionic conductivities than their bare SE counterparts because of decreased grain boundary resistance, enhanced interfacial contact with electrodes, and decreased degradation at the interface. In this study, we add lithium bis(trifluoromethane sulfonyl)imide and a highly fluorinated ether solvate electrolyte to the surface of Li 7 P 3 S 11 (LPS) and Li 10 GeP 2 S 12 (LGPS) pellets and evaluate their overall cell resistance in Li-Li symmetric cells relative to their bare Li/SE/Li counterparts. Time-resolved electrochemical impedance spectroscopy shows an order of magnitude lower cell resistance for LGPS-solvate than for bare LGPS. In contrast, the LPS-solvate system exhibits a higher cell resistance than bare LPS. Scanning electron microscopy and energy dispersive X-ray spectroscopy show that LGPS allows for the total permeation of the solvate into the bulk SE. Although LPS has smaller grain sizes and higher porosity, it has a higher solubility in 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE), which results in an LPS-TTE interlayer on the surface of the pellet, thereby increasing overall cell resistance. Cyclic voltammetry of the bare and hybrid SE cells shows an order of magnitude higher current density for the LGPS-solvate cell over the bare LGPS. Bare LPS shorts after two cycles, whereas the LPS-solvate cell does not short within the timeframe of the experiment (100 cycles). This study suggests that solvates can be used to improve the cell resistance and current density of SEs by altering the grain boundary structures and the interphase between electrode and electrolyte.
KW - CV
KW - EIS
KW - Solid electrolyte
KW - highly fluorinated ether
KW - hybrid electrolyte
KW - solvate
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U2 - 10.1021/acsami.8b16116
DO - 10.1021/acsami.8b16116
M3 - Article
C2 - 30561181
AN - SCOPUS:85060156340
SN - 1944-8244
VL - 11
SP - 2014
EP - 2021
JO - ACS applied materials & interfaces
JF - ACS applied materials & interfaces
IS - 2
ER -