Novel silane compounds as electrolyte
solvents for Li-ion batteries
Khalil Amine, Qingzheng Wanga, Donald R. Vissersa, Zhengcheng Zhangb,
Nicholas A.A. Rossib and Robert Westb
aChemical Engineering Division, Argonne National Laboratory,
Electrochemical Technology Program, Argonne, IL 60439, United States
bOrganosilicon Research Center, Department of Chemistry, University
of Wisconsin, Madison, WI 53706, United States
Abstract
Novel silane compounds such as {2-[2-(2-methoxyethoxy)ethoxy]ethoxy}
trimethylsilane (1), bis{2-[2-(2-methoxyethoxy)ethoxy]ethoxy}dimethylsilane (2),
{3-[2-(2-(2-methoxyethoxy)ethoxy)ethoxy]-propyl}trimethylsilane (3) and
{[2-(2-(2-methoxyethoxy)ethoxy)ethoxy]-methyl} trimethylsilane (4) have been
synthesized and used as non-aqueous electrolyte solvents in lithium-ion
batteries. These silane molecules can easily dissolve most lithium salts
including lithium bis(oxalato)borate (LiBOB), LiPF6, LiBF4,
and lithium trifluoromethylsulfonimide. The LiBOB salt was found to be very
appropriate for these silane molecules because, unlike LiPF6, LiBOB
can provide a good passivation film on a graphite anode. Cyclic voltammetry
analyses show that silane-based electrolytes with a 0.8 M LiBOB salt
concentration are stable to 4.4 V; they also exhibit very high lithium-ion
conductivities up to 1.29 × 10−3 S/cm at room temperature. Full cell
performance tests with LiNi0.08Co0.15Al0.05O2
as the positive electrode and MCMB graphite as the negative electrode have shown
excellent cyclability both at room temperature and at 40 °C. Cells with these
new silane electrolytes exhibit long calendar life; they show no impedance rise
after aging at 80% state of charge and 55 °C for one year. The results suggest
that silane-based electrolytes have great potential for use in lithium-ion
batteries.
Copyright © 2006 Elsevier B.V.
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