Multiple Roles of Superoxide on Oxygen Reduction Reaction in Li+-Containing Nonaqueous Electrolyte: Contribution to the Formation of Oxide as Well as Peroxide

详细信息    查看全文

• 作者：V. S. Dilimon ; Dong-Gyu Lee ; Sung-Dae Yim ; Hyun-Kon Song
• 刊名：Journal of Physical Chemistry C
• 出版年：2015
• 出版时间：February 19, 2015
• 年：2015
• 卷：119
• 期：7
• 页码：3472-3480
• 全文大小：428K
• ISSN：1932-7455

文摘

Oxygen reduction reaction (ORR) on carbon in lithium-ion-containing nonaqueous electrolytes is supposed to follow a three-step mechanism: oxygen (O₂⁰) to superoxide (O₂^{鈥?/sup> or LiO₂) to peroxide (O₂2鈥?/sup> or Li₂O₂) to oxide (O2鈥?/sup> or Li₂O). This work attempts to solve three controversial issues: (1) whether the superoxide is really formed; (2) whether the superoxide can be stable or immediately converts to peroxide; (3) whether the formation of oxide is feasible at the typical discharge potentials of lithium鈥揳ir battery or the discharge product is only peroxide. ORR on carbon was studied in LiClO₄ or LiPF₆ containing dimethyl sulfoxide. The staircase cyclic voltammetry combined with Fourier transform electrochemical impedance spectroscopy (SCV-FTEIS) was used for the in situ investigation of ORR during potential scans. Oxygen was quasi-reversibly reduced to superoxide in the first step. Superoxide showed chemical stability in electrolyte. The superoxide was further reduced to surface-adsorbed peroxide, and the reduction proceeded to produce oxide at higher overpotentials. We identified a novel chemical route resulting in oxide formation even at not-enough overpotentials: peroxide is reduced to oxide by superoxide as an in situ formed one-electron reducing agent. The electrolyte/electrode decomposition product, Li₂CO₃, was observed only in electrolyte with LiClO₄.}