Page 18 - Industrial Technology April 2021 issue

DESIGN ENGINEERING

‘VEGGIE’ BATTERY

BATTERIES

RECYCLABLE ‘VEGGIE’ BATTERY TECHNOLOGY COULD
POWER FUTURE DEVICES MORE EFFICIENTLY

new type of 3D-printed battery which uses electrode, thereby limiting the
electrodes made from vegetable starch and specific energy of lithium-ion
carbon nanotubes could provide mobile devices batteries. Increasing
Awith a more environmentally-friendly, higher- electrodes’ thickness also
capacity source of power. A team of engineers led from the decreases their strain-
University of Glasgow have developed the battery in a bid tolerance, making them more
to make more sustainable lithium-ion batteries capable of prone to cracking. Once an
storing and delivering power more efficiently. electrode breaks, the battery is
Lithium-ion batteries provide a useful combination of rendered useless.
lightweight, compact form factors and the ability to The Glasgow-led team’s
withstand many cycles of charging and discharging. That battery aims to strike a better
has made them ideally suited for use in a wide array of balance between the size and
devices, including laptops, mobile phones, smart the surface area of electrodes
watches, and electric vehicles. by introducing tiny nanoscale
Like many batteries, lithium-ion batteries comprise a and microscale holes, or pores,
positive electrode, often made from lithium into their design. By riddling
cobalt/manganese oxide or lithium iron phosphate, and a the surface and interior of the
negative electrode, often made from lithium metal. During electrodes with pores, they can
charging, lithium ions flow through an electrolyte from the greatly increase the surface
positive electrode to the negative electrode where they are area compared to a solid electrode of the same external Optical and SEM images of 3D printed cellular nanocomposites
stored. During use, the ions flow in the opposite direction, dimensions. (300 µm thickness)
generating energy to power devices through an To do so, they used an additive manufacturing
electrochemical reaction. technique to tightly control the size and placement of each same thickness. The increased porosity, and thus the
One of the physical limitations on the amount of and every pore in their electrodes. They loaded their 3D larger surface area, of the thickest 300-micron electrode
energy current designs of lithium-ion batteries can store printer with a material they developed which combines also influenced the battery’s areal capacity. The thicker
and release is the thickness of their electrodes. Thicker polylactic acid, lithium-iron phosphate and carbon electrode was capable of storing 4.4 milliampere-hour per
electrodes restrict diffusion of lithium ions across the nanotubes. The polylactic acid is a biodegradable material square centimetre (mAh/cm 2 ) compared to 1.7 mAh/cm 2
processed from the starch of corn, sugar cane, and sugar achieved in the 100-micron electrode, a gain of 158
High resolution SEM images (cross-sectional) of 3D printed cellular beet, increasing the battery’s recyclability. percent.
nanocomposites with (a) 3, (b) 5, (c) 7, and (d) 10% CNT loading They experimented with making circular electrodes at The research was led by Dr Shanmugam Kumar from
three different thicknesses of the University of Glasgow’s James Watt School of
100, 200 and 300 microns. Engineering, alongside colleagues from Khalifa University
Each electrode was tested with of Science and Technology in Abu Dhabi, and Texas A&M
different combinations of University and Arizona State University in the USA. Dr
materials, varying the amount Kumar said: “Lithium-ion batteries are increasingly
of carbon nanotubes in the common in everyday life and are likely to continue to
material mixture from 3 to 10 increase in ubiquity as we move towards more
percent by weight, and the electrification of transport and a more sustainable world.
porosity from 10 to 70 percent However, lithium-ion batteries have their own
by introducing tightly-controlled sustainability issues, so it’s important that we look to find
grids of holes throughout the new ways to make them better and more environmentally-
electrode. friendly.
The team’s 300-micron “The 3D printing process we’ve used in this research
electrode battery with 70% gives us a remarkable amount of control over the
porosity performed the best electrodes’ porosity, allowing us to engineer very precisely
during testing, with a specific a new metamaterial capable of addressing some of the
capacity of 151 milliampere- shortcomings of the current generation of lithium-ion
hour per gram (mAh/g) – the batteries. We’ve created a battery with a high specific
standard measurement of how capacity and areal capacity with excellent cyclability.
much charge a battery can “These are promising initial results, and we’re keen to
hold. That is around two to continue to explore the possibilities that this kind of
three times the performance of microarchitected materials offer to create better, more
a traditional lithium-ion battery recyclable batteries for future consumers.”
with a solid electrode of the MORE INFORMATION: www.glasgow.ac.uk

18 INDUSTRIAL TECHNOLOGY • March/April 2021