BATTERY
HEALTH & SAFETY
Research into how lithium batteries age is throwing up some
interesting findings, as Neil Tyler discovers
is another area of interest but
being able to capture energy
from electromagnetic waves is
challenging. A team of researchers
have developed a rectenna (radio
wave harvesting antenna) that is only
several atoms thick and could be
incorporated into devices so that AC
power can be harvested from Wi-Fi in
the air and converted to DC to power
a device directly.
These are just a sample of the
range and variety of technologies
that are under investigation or being
developed, but lithium-ion batteries
remain everywhere and the number of
use cases continues to grow.
All lithium-ion batteries wear down
over time and lose capacity, so a lot
of the research is focused on their
management.
Battery performance degrades
Above: Top view of
ILL’s high flux reactor
due to what is a complex network of
subtle chemical processes, each of
which do not have much of an effect
on a battery’s performance, but
collectively can severely shorten its
performance and lifespan.
The lifespan of a battery is usually
specified in charge cycles, where one
cycle is a charge to a specific level
and full discharge to termination
voltage. For example, if a battery lasts
250 cycles, you can recharge it 250
times before the capacity drops below
the end of life level.
How that cycle rating is measured
is rarely specified for many devices,
but it is possible to use knowledge
built up over time about how lithiumion
batteries behave to better manage
the cycle life.
It is known, for example, that
charging to a specific voltage will
Lithium-ion batteries are popular
because they have a number of
important advantages. They’re
lighter when compared to other types
of rechargeable battery and lithium,
being highly reactive, can store a lot
of energy in its atomic bonds.
While these are obvious
advantages lithium batteries are not
as robust as some other technologies
and require protection from being
over-charged and discharged too far.
Market requirements for batteries
are changing rapidly so a growing
body of research has been focused
on finding alternatives to lithium, and
while there’s not been a significant
advance in battery technology in
recent years many believe that we are
on the verge of a ‘power revolution’.
Lithium-ion batteries are found
everywhere - they are used to power
smart phones, laptops, wearable
device and cars, and work by storing
energy in a very small space.
However, these batteries are
problematic for some industries
in particular for technology and
automotive companies, especially
the latter which is looking to exploit
developments in electric vehicles. For
many consumer devices, while they
are becoming more efficient, charging
is still required every 1-2 days for
smartphones and other forms of
wearable devices.
Some of the battery technologies
that are showing promise include
lithium-sulphur batteries, which
have a lower environmental impact
than lithium and researchers in
the US have been able to develop
a lithium-sulphur battery that can
power a smartphone for up to 5 days,
outperforming lithium-ion and which
is, in turn, cheaper to manufacture.
IBM Research is claiming to have
discovered a new battery chemistry
that is free from heavy metals like
nickel and cobalt and which, they say,
can be charged faster than lithiumion
and is able to pack in both higher
power and energy densities.
Wireless inductive charging
10 28 April 2020 www.newelectronics.co.uk
© T.Arlt, I. MankeHZB, R. ZiescheUCL
/www.newelectronics.co.uk