采用密度泛函理论方法，研究锂离子电池碳酸丙烯酯（PC）基电解液体系中锂盐离子与溶剂分子静电相互作用形成的可能结构. 计算结果表明，电解液中溶剂分子-离子的结构取决于体系的溶剂分子数. 在PC基电解液，Li+最多只能与4个PC溶剂分子相结合，锂盐阴离子与带正电的PC分子烷基基团相结合，而不以自由离子形式存在. 本文的计算结果能很好地解释文献报道的实验结果.
In this work, the possible structures of solvent-ion complex, resulting from the electrostatic interaction in the propylene carbonate (PC) base electrolyte of lithium ion battery, have been investigated using the density functional theory. The calculated results show that the structure of solvent-ion complex depends on the solvent number. In the PC base electrolyte, maximum number of PC solvents that coexist in the Li+-solvent sheath is four. Additionally, the salt anion exists in a complex with the positively charged alkyl group of PC rather than in a free state. The calculated results give a good explanation to the reported experimental observations.
[1] Li W S(李伟善). Research progresses on materials of lithium ion battery for energy storage[J]. Advance in New and Renewable Energy(新能源进展), 2013, 1(1): 95-105.
[2] Xing L D(邢丽丹), Xu M Q(许梦清), Li W S(李伟善). Research processes on high-voltage electrolyte of lithium ion battery[J]. Science in China B(中国科学B辑 化学), 2014, 44(8): 1289-1297.
[3] Xu K, Lam Y F, Sheng S, et al. Solvation sheath of Li+ in nonaqueous electrolytes and its implication of graphite/electrolyte interface chemistry[J]. Journal of Physical Chemistry C, 2007, 111(20): 7411-7421.
[4] Xing L D, Vatamanu J, Bedrov D, et al. Electrode/electrolyte interface in sulfolane-based electrolytes for Li ion batteries: A molecular dynamics simulation study[J]. Journal of Physical Chemistry C, 2012, 116(45): 23871-23881.
[5] Xing L D, Borodin O, Grant S, et al. A density function theory study of the role of anions on the oxidative decomposition reaction of propylene carbonate[J] Journal of Physical Chemistry A, 2011, 115(47): 13896-13905.
[6] Wang Y T, Xing L D, Li W S, et al. Why do sulfone-based electrolytes show stability at high voltages? Insight from density functional theory[J]. Journal of Physical Chemistry Letter, 2013, 4(22): 3992-3999.
[7] Li S, Cao Z, Peng Y, et al. Molecular dynamics simulation of LiTFSI-acetamide electrolytes: Structural properties[J]. Journal of Physical Chemistry B, 2008, 112(20): 6398-6410.
[8] Tsunekawa H, Narumi A, Sano M, et al. Solvation and ion association studies of LiBF4-propylenecarbonate and LiBF4-propylene carbonate-trimethyl phosphate solutions[J]. Journal of Physical Chemistry B, 2003, 107(39): 10962-10966.
[9] Wang Y X, Balbuena P B. Theoretical insights into the reductive decompositions of propylene carbonate and vinylene carbonate: Density functional theory studies[J]. Journal of Physical Chemistry B, 2002, 106(17): 4486-4495.
[10] Fukushima T, Matsuda Y, Hashimoto H, et al. Studies on solvation of lithium ions in organic electrolyte solutions by electrospray ionization-mass spectroscopy[J]. Electrochemical and Solid-State Letter, 2001, 4(8): A127-A128.
[11] Li T, Balbuena P B. Theoretical studies of lithium perchlorate in ethylene carbonate, propylene carbonate, and their mixtures[J]. Journal of The Electrochemical Society, 1999, 146(10): 3613-3622.
[12] Masia M, Probst M, Rey R. Ethylene carbonate-Li+: A theoretical study of structural and vibrational properties in gas and liquid phases[J]. Journal of Physical Chemistry B, 2004, 108(6): 2016-2027.
[13] Brooksby P A, Fawcett W R. Infrared (attenuated total reflection) study of propylene carbonate solutions containing lithium and sodium perchlorate[J]. Spectrochim Acta A, 2006, 64(2): 372-382.
[14] Kondo K, Sano M, Hiwara A, et al. Conductivity and solvation of Li+ ions of LiPF6 in propylene carbonate solutions[J]. Journal of Physical Chemistry B, 2000, 104(20): 5040-5044.
[15] Xing L D, Li W S, Wang C Y, et al. Theoretical investigations on oxidative stability of solvents and oxidative decomposition mechanism of ethylene carbonate for lithium-ion battery use[J]. Journal of Physical Chemistry B, 2009, 113(52): 16596-16602.
[16] Frisch M J, Trucks G W, Schlegel H B, et al. Gaussian 09, Revision A[CP]. Gaussian, Inc., Wallingford, CT, 2009.
[17] Bogle X, Vazquez R, Greenbaum S, et al. Understanding Li+-solvent interaction in nonaqueous carbonate electrolytes with 17O NMR[J]. Journal of Physical Chemistry Letter, 2013, 4(10): 1664-1668.
[18] Naejus R, Coudert R, Willmann P, et al. Ion solvation in carbonate-based lithium battery electrolyte solutions[J]. Electrochimica Acta, 1998, 43(3/4): 275-284.
