B A T T E R I E S
NANOCHAINS
Frigel is calling itself the process cooling
pioneer – and it just might be right - by
introducing the Ecodry System for the
plastics industry.
How long the battery of your phone or computer
lasts depends on how many lithium ions can
be stored in the battery’s negative electrode
material. If the battery runs out of these ions, it
can’t generate an electrical current to run a device
and ultimately fails.
Materials with a higher lithium ion storage
capacity are either too heavy or the wrong
shape to replace graphite, the electrode material
currently used in today’s batteries.
Purdue University scientists and engineers have
introduced a potential way that these materials
could be restructured into a new electrode design
that would allow them to increase a battery’s
lifespan, make it more stable and shorten its
charging time.
The study, appearing as the cover of the
September issue of Applied Nano Materials,
created a net-like structure, called a “nanochain,”
of antimony, a metalloid known to enhance lithium
ion charge capacity in batteries. The researchers
compared the nanochain electrodes to graphite
electrodes, finding that when coin cell batteries
with the nanochain electrode were only charged
for 30 minutes, they achieved double the lithiumion
capacity for 100 charge-discharge cycles.
Some types of commercial batteries already use
carbon-metal composites similar to antimony
metal negative electrodes, but the material tends
to expand up to three times as it takes in lithium
ions, causing it to become a safety hazard as the
battery charges.
“You want to accommodate that type of
expansion in your smartphone batteries. That way
you’re not carrying around something unsafe,”
says Vilas Pol, a Purdue associate professor of
chemical engineering.
Through applying chemical compounds – a
reducing agent and a nucleating agent – Purdue
scientists connected the tiny antimony particles
into a nanochain shape that would accommodate
the required expansion. The particular reducing
agent the team used, ammonia-borane, is
responsible for creating the empty spaces – the
pores inside the nanochain – that accommodate
expansion and suppress electrode failure.
The team applied ammonia-borane to several
different compounds of antimony, finding that
only antimony-chloride produced the nanochain
structure.
“Our procedure to make the nanoparticles
consistently provides the chain structures,”
says P. V. Ramachandran, a professor of organic
chemistry at Purdue.
The nanochain also keeps lithium ion capacity
stable for at least 100 charging-discharging
cycles. “There’s essentially no change from cycle
1 to cycle 100, so we have no reason to think that
cycle 102 won’t be the same,” Pol said.
Henry Hamann, a chemistry graduate student
at Purdue, synthesized the antimony nanochain
structure and Jassiel Rodriguez, a Purdue
chemical engineering postdoctoral candidate,
tested the electrochemical battery performance.
The electrode design has the potential to be
scalable for larger batteries, the researchers say.
The team plans to test the design in pouch cell
batteries next.
COULD INCREASE BATTERY CAPACITY,
CUT CHARGING TIME
Artistic depiction of a coin cell battery
with a copper electrode (left) containing
a black nanochain structure, which
researchers have discovered could
increase the capacity of a battery and
cut charging time. (Purdue University
illustration/Henry Hamann)
40 November 2019