ANALYTICAL TOOLS FOR COMPREHENSIVE
CHARACTERIZATION OF LI-ION BATTERIES
The increased demand for portable electronic devices, including mobile phones, laptops and new ‘wearables’, has
required advances in battery technology to provide a low-cost, lightweight, long-lasting and stable power source.
With fossil fuels dwindling and CO 2 regulations becoming more stringent, battery technology is increasingly being
used in applications such as renewable energy storage and electric vehicles, which require ever more lightweight,
safe, high-power and fast-charging batteries.
Schematic of a Li-ion battery. During
discharge, lithium ions (Li + ) move from
the anode to the cathode, conducted
via the electrolyte, with flow in the
reverse direction occurring when the
battery is charged. Anodes are typically
graphite-based, while cathodes are
often manufactured using lithium-
iron phosphate, lithium-cobalt oxide,
lithium-manganese oxide, lithium-nickel
cobalt manganese oxide, etc.
The cornerstones of battery performance are power, which
impacts current and discharge characteristics, and energy Manufacture of the cathodes and anodes involves mixing
the active electrode material with some form of conductive
storage capacity. Battery power is determined by the rate of
reaction between the electrodes and the electrolyte, while
storage capacity is a function of the volume of electrolyte
within the cell. These properties are intrinsically linked to additive such as carbon (e.g. carbon black and/or graphite) and
a polymeric binder dissolved in a solvent to form a slurry. The
slurry/suspension is then applied to a metal foil in a continuous
coating process and the solvent driven off to produce a dried
coating which is subjected to calendaring, a compression
process that involves feeding the coated foil through a series of
rollers. The electrodes are then punched or cut to size prior to
the intercalation structure and primary particle size of the
electrode particles, which determine how well the mobile
ions are taken up and released by the electrode 1 . Particle
size distribution and particle shape also influence particle
packing and hence the volume of electrolyte that can be
accommodated within the interstitial voids of the electrode,
which affects storage capacity.
Particle sizing of electrode materials is commonly performed
using laser diffraction technology, such as the Mastersizer 3000;
although the Zetasizer Pro and Zetasizer Ultra can also be
employed for analyzing the much smaller particles used for
electrode materials or separators. Automated imaging
(Morphologi 4) is commonly employed for particle shape
analysis but can also be coupled with Raman spectroscopy to
give particle-specific structural information. The primary tool for
studying the structure of electrode materials, however, is X-ray
diffraction (XRD) with Aeris or Empyrean diffractometers widely
used in this sector. Empyrean also allows small-angle X-ray
scattering (SAXS), an important tool for evaluating the primary
particle size or crystallite size of nanoparticle electrodes which
tend to exist in aggregated form.
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winding or stacking between the separator film before inserting
into the case, wetting with electrolyte, and sealing. The cells are
then activated over several weeks through a series of charge/
discharge cycles.
These processes exert a significant influence on electrode
structure and are related to the rheological, or flow properties,
of the battery slurry. These properties can be influenced by the
extent to which raw materials are dispersed during the slurry
manufacturing process, affecting the size of particles deposited
on the foil or the impact of compressive forces applied during
calendaring, which affects the porosity of the finished coating.
These are not discrete effects - rather changes made during one
step can have an impact on consecutive processes, as well as the
properties of the finished electrode 2 .