|M.Sc Student||Yehezkel Shani|
|Subject||Development of Carbon Fabric as a Lightweight Highly|
Conductive Current Collector for Li-ion Battery
|Department||Department of Energy||Supervisor||Professor Yair Ein-Eli|
|Full Thesis text|
Nowadays, Lithium-Ion is the most commonly used battery type. However, energy demands by portable electronic devices and mostly electric vehicles are getting higher with the advancements of those technologies, making the current Li-Ion technology insufficient, and therefore requiring the development of an improved Li-ion battery with higher specific energy. Carbon nanotubes (CNT) fabrics were studied and evaluated as anode current collectors, replacing the traditional copper foil current collector in Li-ion batteries. CNT fabrics are highly conductive, ultra-light weighted, thin, flexible and cost effective and therefore considered a superior candidate in the replacement of the copper foil. In this research, two approaches towards the implementation of the CNT fabric as the current collector were studied.
approach suggests the use of a bare CNT fabric current collector aiming for
Galvanostatic measurements reveal high values of irreversible capacities (as
high as 28%), resulted mainly from the formation of the solid electrolyte interphase
(SEI) layer at the CNT fabric surface. Various pre-treatments to the CNT fabric
prior to active anode material loading have shown that the lowest irreversible
capacity is achieved by immersing and washing the CNT fabric with iso-propanol
(IPA) or tert-butanol (T-butanol), which dramatically modified the fabric
surface. Additionally, the use of very thin CNT fabrics (5 µm) results in a
substantial irreversible capacity minimization. A combination of IPA rinse
action and utilization of the thinnest CNT fabric provides the lowest
irreversible capacity of 13%.
approach suggests the use of a
CNT fabric current collector aiming for high power applications.
Electrodeposition of copper on the surface of carbon nanotubes (CNT) fabrics is
demonstrated upon immersion in two copper electrolytes: acid copper
sulfate (pH 0.5) and alkaline copper pyrophosphate (pH 8.6). The
cathodic electrochemical behavior of the CNT fabric in the two electrolytes was
evaluated and potentiodynamic characteristics were presented. Potentiostatic
copper deposition on the outer surface of the CNT fabrics revealed different
surface morphologies obtained from the two electroplating baths. Other factors
affecting the copper surface morphology were presented such as CNT cleaning
procedure, CNT thickness and various electrolyte additives. It was established
that the deposited copper films are characterized by high uniformity,
homogeneity and planarity and excellent adhesion of the copper films to CNT fabric
was obtained. Finally, the performance of the coated CNT fabric as the anode
current collector in a Li-ion battery is demonstrated.
The novelty of this research lies in improving both gravimetric and volumetric energy densities of the Li-ion battery without changing the chemistry of the cell. Furthermore, this research reports on two simple procedures to overcome the high irreversible capacity value while using graphite active material, and therefore preserve the high voltage when a CNT fabric current collector is used.