Premium
Mechanistic Study Revealing the Role of the Br 3 − /Br 2 Redox Couple in CO 2 ‐Assisted Li–O 2 Batteries
Author(s) -
Marques Mota Filipe,
Kang JinHyuk,
Jung Younguk,
Park Jiwon,
Na Moony,
Kim Dong Ha,
Byon Hye Ryung
Publication year - 2020
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201903486
Subject(s) - redox , catalysis , electrolyte , overpotential , materials science , lithium (medication) , inorganic chemistry , chemical engineering , chemistry , electrochemistry , electrode , organic chemistry , medicine , engineering , endocrinology
Abstract Replacing oxygen (O 2 ) with air is a critical step in the development of lithium (Li)–air batteries. A trace amount of carbon dioxide (CO 2 ) in the air is, however, influentially involved in the O 2 chemistry, which indicates that a fundamental understanding of the effect of CO 2 is required for the design of practical cells. When up to 30% CO 2 is added to Li–O 2 cells, CO 2 acts as an O 2 − scavenger. Their chemical reactions form soluble products, CO 4 2− and C 2 O 6 2− , in the tetraglyme electrolyte solution, and enhance full capacity and cell cyclability. A critical challenge is, however, the sluggish decomposition of the coproduct Li 2 CO 3 during recharge. To lower the charging overpotential, a Br 3 − /Br 2 redox couple is incorporated and its redox behavior is investigated using spectroscopic methods. The redox shuttle of Br 3 − /Br 2 decomposes amorphous Li 2 CO 3 more efficiently than its crystalline counterpart. It is revealed that Br 2 combines with Br 3 − to form a Br 2 ···Br 3 − complex, which acts as a mobile catalyst in the electrolyte solution without swift precipitation of the nonpolar Br 2 . This comprehensive study, revealing the molecular structure and redox process of mobile catalysts, provides an insight into improving the design of redox couples toward superior cycling performance.