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<p>The majority of consumer electronic devices, electric vehicles, and aerospace electronics
are powered by lithium ion batteries because of their high energy and power densities.
Commercially available lithium ion batteries consist of electrodes, separators and
current collectors fabricated in multilayer rolls that are packaged in cylindrical
or rectangular cases. The size and shape of the package as well as the composition
of the electrode has a significant impact on the battery life and design of the products
they power. For example, the battery life and shape of portable electronics such as
cell phones or laptops, is governed by the volume that is dedicated to the battery.
In the case of electric vehicles, decreasing the size and weight of the battery while
increasing capacity is an engineering challenge that affects vehicle range and cost.
Therefore, the of my dissertation consists of the development of a novel 3D printable
lithium ion battery nanocomposites and the integration of conductive metal nanomaterials
into conventional lithium ion anodes. Here, we report the development of PLA-anode,
cathode, and separator materials that enable 3D printing of complete lithium ion batteries
with a low-cost FFF printer for the first time. The most common 3D printing polymer
polylactic acid (PLA) is an insulator. However, our work demonstrates that 3D printed
PLA can be infused with a mixture of ethyl methyl carbonate, propylene carbonate,
and LiClO4 provides an ionic conductivity of 2.3 x 10−4 S cm−1 which is comparable
to that of polymer and hybrid electrolytes (10−3 to 10−4 S cm−1). It was found that
up to 12-30 volume % of solids, depending on the filler morphology, could be mixed
into PLA without causing it to clog during 3D printing. It was also found that not
only is electrical conductivity crucial to the performance of a 3D printed lithium
ion battery, but efficient electrical contact to the active materials is as well.
To that effect, we investigated the effect of aspect ratio of silver-copper core-shell
nanowires on the performance enhancement of a commercially fabricated graphite lithium
ion anodes. Currently, carbon is the most common conductive filler used in commercial
lithium ion battery anodes. We hypothesize that a more conductive, high aspect ratio
would improve the performance of a lithium ion battery. We examined the effect of
exchanging carbon with CuAg nanowires as the conductive filler in graphite lithium
ion batteries. We tested 4 different aspect ratios and found that not only does aspect
ratio matter, diameter and length have profound effect on capacity and energy of the
anode at the same volume percent as carbon conductive filler.</p>
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