| Summary: | 博士 === 國立清華大學 === 化學工程學系 === 85 === This work examines the formation of passive film on the carbon
electrode of lithium batteries. According to those results,
with a single solvent of EC (ethylene carbonate), the
structure of the passive film was found to be (CH2OCOOLi)2
on the carbon electrode''s surface. In the DEC (diethyl
carbonate) or DMC(dimethyl carbonate) system, C2H5OCOOLi and Li2
CO3 were formed on the carbon electrode''s surface. According to
mass spectra, CO2 gas is the main product when EC is
decomposed. In addition , DEC is decomposed into CO and C2H6
and DMC into CO and CH4 as well. Those results suggest the
composition ofpassive film depends on the solvent''s property. In
a binary solvent system which contains EC, the passive film
still contains chiefly (CH2OCOOLi)2, which is identical to
a single EC solventsystem. This
work examines the interface between carbon electrode and organic
electrolyte of lithium ion battery by AC impedance technology. A
five RC circuits model was adopted to investigate the
interfacial property. It was found in EC or DMC electrolyte
system, the total interfacial resistance and the passive film''
s thickness increase with a decreasing intercalation
potential. However, in DEC system, the total interfacial
resistance and the passive film''s thickness decrease as
intercalation proceeds. The porous layer of the passive film
obviously affects the total interfacial resistance in a single
which organic electrolyte. Furthermore, the total interfacial
resistance and the passive film''s thickness remain constant
after the initial intercalation. This finding suggests that the
passive film''s property is steady in a single electrolyte
system. In the binary electrolyte system such as EC/DEC or EC/
DMC system, the effects of porous parts on the total
interfacial resistance are slight. However, the total
interfacial resistance and the passive film''s thickness are
smaller than that in a single electrolytesystem. In addition,
the variation of the total interfacial resistance and the
passive film''s thickness in EC/DEC (or EC/DMC) electrolyte are
similar to DEC (or DMC) electrolyte during intercalation
progress, respectively.
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