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Redox Mediators for Li–O 2 Batteries: Status and Perspectives
Author(s) -
Park JinBum,
Lee Seon Hwa,
Jung HunGi,
Aurbach Doron,
Sun YangKook
Publication year - 2018
Publication title -
advanced materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.707
H-Index - 527
eISSN - 1521-4095
pISSN - 0935-9648
DOI - 10.1002/adma.201704162
Subject(s) - oxidizing agent , redox , battery (electricity) , materials science , electrolyte , organic radical battery , electrocatalyst , catalysis , electrochemistry , chemical engineering , energy storage , nanotechnology , carbon fibers , electrode , inorganic chemistry , power (physics) , chemistry , metallurgy , organic chemistry , composite material , thermodynamics , physics , composite number , engineering
Li–O 2 batteries have received much attention due to their extremely large theoretical energy density. However, the high overpotentials required for charging Li–O 2 batteries lower their energy efficiency and degrade the electrolytes and carbon electrodes. This problem is one of the main obstacles in developing practical Li–O 2 batteries. To solve this problem, it is important to facilitate the oxidation of Li 2 O 2 upon charging by using effective electrocatalysis. Using solid catalysts is not too effective for oxidizing the electronically isolating Li‐peroxide layers. In turn, for soluble catalysts, red‐ox mediators (RMs) are homogeneously dissolved in the electrolyte solutions and can effectively oxidize all of the Li 2 O 2 precipitated during discharge. RMs can decompose solid Li 2 O 2 species no matter their size, morphology, or thickness and thus dramatically increase energy efficiency. However, some negative side effects, such as the shuttle reactions of RMs and deterioration of the Li‐metal occur. Therefore, it is necessary to study the activity and stability of RMs in Li–O 2 batteries in detail. Herein, recent studies related to redox mediators are reviewed and the mechanisms of redox reactions are illustrated. The development opportunities of RMs for this important battery technology are discussed and future directions are suggested.