Lithium-ion batteries have gained considerable popularity for powering everything from portable electron devices, to hybrid and electric vehicles, to storage from power sources. The useful tools are not perfect, however, and researchers around the world strive to improve their recharging times, capacity, environmental impact, safety and costs.
Developing better materials for lithium-ion batteries requires a number of analytical methods, evaluation materials and a better understanding of the mechanisms involved in charge/discharge cycles.
Bulk analysis of components is a first step, but it is also important to understand surface interactions and interfaces. Electrochemical evaluation of cells includes conductivity measurements, electrochemical stability of components, cell capacity, ion mobility, discharge rates, and cycling behavior.
Materials characterization of the various cell components can include analytical techniques such as X-ray photoelectron spectroscopy, x-ray fluorescence, x-ray diffraction, microCT, electron microscopy, energy dispersive (x-ray) spectroscopy, AFM, TGA and DSC.
One technique rapidly growing in popularity for its analysis of materials, Raman spectroscopy, exhibits many advantages for battery applications. Raman analysis can involve subtle changes in molecular structure or local chemical environments. The spectral results can usually be correlated with the electrochemical performance.
A commonly used material for lithium-ion battery anodes is graphite, however other allotropes of carbon are being investigated for anode materials as battery improvements. Here, Raman spectroscopy stands out as an excellent choice for analyzing the different allotropes of carbon. Various carbon coatings using graphene, single- and multi-wall carbon nanotubes, diamond-like carbon or fullerenes (C60) have been analyzed on anode materials such as silicon, tin dioxide and tin disulfide. Raman spectroscopy has also been used to report on improvements in the conductivity of lithium transition metal oxides such as Li4Ti5O12 using carbon coatings.