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Title: Electrochemical Oxidation of Lithium Carbonate Generates Singlet Oxygen

Solid alkali metal carbonates are universal passivation layer components of intercalation battery materials and common side products in metal-O 2 batteries, and are believed to form and decompose reversibly in metal-O 2/CO 2 cells. In these cathodes, Li 2CO 3 decomposes to CO 2 when exposed to potentials above 3.8 V vs. Li/Li +. However, O 2 evolution, as would be expected according to the decomposition reaction 2 Li 2CO 3 → 4 Li ++4 e +2 CO 2+O 2, is not detected. O atoms are thus unaccounted for, which was previously ascribed to unidentified parasitic reactions. Here, we show that highly reactive singlet oxygen ( 1O 2) forms upon oxidizing Li 2CO 3 in an aprotic electrolyte and therefore does not evolve as O 2. These results have substantial implications for the long-term cyclability of batteries: they underpin the importance of avoiding 1O 2 in metal-O 2 batteries, question the possibility of a reversible metal-O 2/CO 2 battery based on a carbonate discharge product, and help explain the interfacial reactivity of transition-metal cathodes with residual Li 2CO 3.
Authors:
ORCiD logo [1] ; ORCiD logo [2] ; ORCiD logo [2] ; ORCiD logo [1]
  1. Graz Univ. of Technology, Graz (Austria)
  2. Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Univ. of California, Berkeley, CA (United States)
Publication Date:
Grant/Contract Number:
AC02-05CH11231
Type:
Published Article
Journal Name:
Angewandte Chemie (International Edition)
Additional Journal Information:
Journal Name: Angewandte Chemie (International Edition); Journal Volume: 57; Journal Issue: 19; Related Information: © 2018 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.; Journal ID: ISSN 1433-7851
Publisher:
Wiley
Research Org:
Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
Language:
English
Subject:
25 ENERGY STORAGE; electrochemistry; lithium batteries; lithium carbonate; reaction mechanisms; singlet oxygen
OSTI Identifier:
1433266
Alternate Identifier(s):
OSTI ID: 1433267; OSTI ID: 1460317