文章基本信息

标题：Tuning anion solvation energetics enhances potassium–oxygen battery performance
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作者：Shrihari Sankarasubramanian ; Shrihari Sankarasubramanian ; Joshua Kahky 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2019
卷号：116
期号：30
页码：14899-14904
DOI：10.1073/pnas.1901329116
出版社：The National Academy of Sciences of the United States of America
摘要：The oxygen reduction reaction (ORR) is a critical reaction in secondary batteries based on alkali metal chemistries. The nonaqueous electrolyte mediates ion and oxygen transport and determines the heterogeneous charge transfer rates by controlling the nature and degree of solvation. This study shows that the solvent reorganization energy ( λ ) correlates well with the oxygen diffusion coefficient ( D O 2 ) and with the ORR rate constant ( k ) in nonaqueous Li–, Na–, and K–O2 cells, thereby elucidating the impact of variations in the solvation shell on the ORR. Increasing cation size (from Li+ to K+) doubled k / λ , indicating an increased sensitivity of k to the choice of anion, while variations in D O 2 were minimal over this cation size range. At the level of a symmetric K–O2 cell, both the formation of solvent-separated ion pairs [K+–(DMSO)n–ClO4− + (DMSO)m–ClO4−] and the anions being unsolvated (in case of PF6−) lowered ORR activation barriers with a 200-mV lower overpotential for the PF6− and ClO4− electrolytes compared with OTf− and TFSI− electrolytes with partial anion solvation [predominantly K+–(DMSO)n–OTf−]. Balancing transport and kinetic requirements, KPF6 in DMSO is identified as a promising electrolyte for K–O2 batteries.
关键词：metal;oxygen battery ; oxygen reduction reaction ; electrochemical kinetics ; solvent reorganization energy