Bogle Xavier, Vazquez Rafael, Greenbaum Steven, Cresce Arthur von Wald, Xu Kang
‡Graduate Center of the City University of New York, New York, New York 10065 and 10016, United States.
§Electrochemistry Branch, U.S. Army Research Laboratory, Adelphi, Maryland 20783, United States.
J Phys Chem Lett. 2013 May 16;4(10):1664-8. doi: 10.1021/jz400661k. Epub 2013 May 1.
To understand how Li(+) interacts with individual carbonate molecules in nonaqueous electrolytes, we conducted natural abundance (17)O NMR measurements on electrolyte solutions of 1 M LiPF6 in a series of binary solvent mixtures of ethylene carbonate (EC) and dimethyl carbonate (DMC). It was observed that the largest changes in (17)O chemical shift occurred at the carbonyl oxygens of EC, firmly establishing that Li(+) strongly prefers EC over DMC in typical nonaqueous electrolytes, while mainly coordinating with carbonyl rather than ethereal oxygens. Further quantitative analysis of the displacements in (17)O chemical shifts renders a detailed Li(+)-solvation structure in these electrolyte solutions, revealing that maximum six EC molecules can coexist in the Li(+)-solvation sheath, while DMC association with Li(+) is more "noncommittal" but simultaneously prevalent. This discovery, while aligning well with previous fragmental knowledge about Li(+)-solvation, reveals for the first time a complete picture of Li(+) solvation structure in nonaqueous electrolytes.
为了理解Li(+)在非水电解质中如何与单个碳酸酯分子相互作用，我们对碳酸亚乙酯（EC）和碳酸二甲酯（DMC）的一系列二元混合溶剂中1 M LiPF6的电解质溶液进行了天然丰度(17)O NMR测量。结果发现，(17)O化学位移的最大变化发生在EC的羰基氧处，这有力地证明了在典型的非水电解质中，Li(+)相比于DMC强烈偏好EC，并且主要与羰基氧而非醚氧配位。对(17)O化学位移位移的进一步定量分析给出了这些电解质溶液中详细的Li(+)-溶剂化结构，表明在Li(+)-溶剂化鞘层中最多可共存六个EC分子，而DMC与Li(+)的缔合则更“不确定”但同时普遍存在。这一发现虽然与先前关于Li(+)-溶剂化的零散知识高度吻合，但首次揭示了非水电解质中Li(+)溶剂化结构的全貌。
