Toward a Lithium鈥撯€淎ir鈥?Battery: The Effect of CO2 on the Chemistry of a Lithium鈥揙xygen Cell

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• 作者：Hyung-Kyu Lim ; Hee-Dae Lim ; Kyu-Young Park ; Dong-Hwa Seo ; Hyeokjo Gwon ; Jihyun Hong ; William A. Goddard ; III ; Hyungjun Kim ; Kisuk Kang
• 刊名：The Journal of the American Chemical Society
• 出版年：2013
• 出版时间：July 3, 2013
• 年：2013
• 卷：135
• 期：26
• 页码：9733-9742
• 全文大小：626K
• 年卷期：v.135,no.26(July 3, 2013)
• ISSN：1520-5126

文摘

Lithium鈥搊xygen chemistry offers the highest energy density for a rechargeable system as a 鈥渓ithium鈥揳ir battery鈥? Most studies of lithium鈥揳ir batteries have focused on demonstrating battery operations in pure oxygen conditions; such a battery should technically be described as a 鈥渓ithium鈥揹ioxygen battery鈥? Consequently, the next step for the lithium鈥撯€渁ir鈥?battery is to understand how the reaction chemistry is affected by the constituents of ambient air. Among the components of air, CO₂ is of particular interest because of its high solubility in organic solvents and it can react actively with O₂^{鈥撯€?/sup>, which is the key intermediate species in Li鈥揙₂ battery reactions. In this work, we investigated the reaction mechanisms in the Li鈥揙₂/CO₂ cell under various electrolyte conditions using quantum mechanical simulations combined with experimental verification. Our most important finding is that the subtle balance among various reaction pathways influencing the potential energy surfaces can be modified by the electrolyte solvation effect. Thus, a low dielectric electrolyte tends to primarily form Li₂O₂, while a high dielectric electrolyte is effective in electrochemically activating CO₂, yielding only Li₂CO₃. Most surprisingly, we further discovered that a high dielectric medium such as DMSO can result in the reversible reaction of Li₂CO₃ over multiple cycles. We believe that the current mechanistic understanding of the chemistry of CO₂ in a Li鈥揳ir cell and the interplay of CO₂ with electrolyte solvation will provide an important guideline for developing Li鈥揳ir batteries. Furthermore, the possibility for a rechargeable Li鈥揙₂/CO₂ battery based on Li₂CO₃ may have merits in enhancing cyclability by minimizing side reactions.}