Structural and electrochemical characterization of graphite materials for Li ion batteries
The purpose of this study is to find a correlation between the crystallite sizes in the
basal plane direction of graphite materials, used in carbon anodes in Lithium-ion
batteries. Carbon anodes are the most common type of anode used in rechargeable
Lithium-ion batteries today. The two major causes of capacity fading in graphite anodes
is structural disordering during cycling and SEI (solid electrolyte interface) formation,
which causes a loss of active graphite material and loss of active lithium-ion
On this basis, the crystallite size in the basal plane direction La of graphite are
measured by structural characterization methods for later comparison with the performance
of the graphite powder when used as a carbon anode. In this work, three characterization
methods have been utilized to characterize four different types of graphite
powders. These three characterization methods are Raman spectroscopy, X-ray powder
diffraction and SEM analysis, with special emphasis on Raman spectroscopy due
to its flexibility when it comes to sample preparation methods. Three different sample
preparation methods have been carried out on the graphite powders before doing
A comparison of the results from the Raman measurements shows a clear trend in
which the calculated R-ratio is dependent on the sample preparation method, where
the R-ratio is largest for samples prepared as carbon anodes. It is very likely that this
trend is attributed to the increase in R-ratio due to mechanical milling of the graphite
powders as a part of the processing steps of the carbon anode sample.
Determining the La value with X-ray powder diffraction is usually a difficult task
due to poor resolution of the diffraction peaks necessary to derive the La value. This
is due to preferred orientation of non-spherical shaped graphite powders when the
powder is applied directly on a Si-sample holder for X-ray diffraction measurements.
However, by air spraying the graphite powders mixed with ethanol, the particle are
more random oriented, giving visible diffraction peaks needed to derive the La value.
It has been shown that Raman spectroscopy is an unreliable method for determining
the La value by comparing the results from X-ray with the results from Raman measurements.
However, if Raman spectroscopic measurements are used together with
X-ray measurements, a new linear relationship between the X-ray measured La value
and the Raman R-ratio can be derived.
Place, publisher, year, edition, pages
Institutt for materialteknologi , 2012. , 76 p.
IdentifiersURN: urn:nbn:no:ntnu:diva-21147Local ID: ntnudaim:6874OAI: oai:DiVA.org:ntnu-21147DiVA: diva2:631284
Vullum, Fride, FørsteamanuensisFossdal, Anita