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Title: Poly(vinylidene fluoride) (PVDF) Binder Degradation in Li–O 2 Batteries: A Consideration for the Characterization of Lithium Superoxide

We show that a common Li–O 2 battery cathode binder, poly(vinylidene fluoride) (PVDF), degrades in the presence of reduced oxygen species during Li–O 2 discharge when adventitious impurities are present. This degradation process forms products that exhibit Raman shifts (~1133 and 1525 cm –1) nearly identical to those reported to belong to lithium superoxide (LiO 2), complicating the identification of LiO 2 in Li–O 2 batteries. We show that these peaks are not observed when characterizing extracted discharged cathodes that employ poly(tetrafluoroethylene) (PTFE) as a binder, even when used to bind iridium-decorated reduced graphene oxide (Ir-rGO)-based cathodes similar to those that reportedly stabilize bulk LiO 2 formation. We confirm that for all extracted discharged cathodes on which the 1133 and 1525 cm –1 Raman shifts are observed, only a 2.0 e /O 2 process is identified during the discharge, and lithium peroxide (Li 2O 2) is predominantly formed (along with typical parasitic side product formation). In conclusion, our results strongly suggest that bulk, stable LiO 2 formation via the 1 e /O 2 process is not an active discharge reaction in Li–O 2 batteries.
Authors:
ORCiD logo [1] ;  [2] ; ORCiD logo [1] ;  [1] ;  [3] ;  [4] ;  [2] ; ORCiD logo [1]
  1. Univ. of California, Berkeley, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
  3. Stanford Univ., Stanford, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
  4. IBM Almaden Research Center, San Jose, CA (United States)
Publication Date:
Grant/Contract Number:
AC02-76SF00515; AC02-05CH11231; DGE-1106400; NNX16AM56H; CBET-1604927
Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry Letters
Additional Journal Information:
Journal Volume: 8; Journal Issue: 6; Journal ID: ISSN 1948-7185
Publisher:
American Chemical Society
Research Org:
SLAC National Accelerator Lab., Menlo Park, CA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE
OSTI Identifier:
1360209