When was the last time that you had change your plans, miss
an event or be late because of your phone battery dying?
Dr Richard Binns, Head of the Department of Mathematics, Physics and Electrical Engineering, and student Arturas Matusevicius explain more about how battery technologies are developing and improving. Arturas is studying on Northumbria's MSC in Electrical Power Engineering.
Be it phones, laptops,
or electric vehicles, they all share a common limitation. Batteries, the one thing
that unanimously powers them. Ever since the mobile phone was invented, their
growth has been phenomenal. Our smart phones, for example, have become an
extension of ourselves that we use to connect to people around us, yet that is
rendered inaccessible at the sight of 1% on the battery indicator, with no
charger nearby.
Most people would not consider buying a diesel or petrol car
which had a fuel tank that has shrunk by 20% after a few years of use (or any reduction,
for that matter). However, that’s the
status quo for modern Lithium-polymer batteries, which may suffer a 20% loss of
capacity in a single year [1]. If our devices malfunction in a dangerous way,
it will be due to the battery [2]. To fulfil
the energy needs for phones both current and past, it’s common to have
batteries that account for 30% of both mass and volume of a smartphone.
Batteries
have come a long way
With all the reasons and flaws that I mentioned earlier, it’s
easy to be disappointed with the current state of battery technology, but
that’s not the full picture. The first handheld phones released by Nokia in
1987 used Nickel-Cadmium batteries, which were prone to degrading rapidly,
having a very short talk-time, and taking hours to charge. However, it’s normal
for any emergent technology to be underdeveloped by current standards. If we take a closer look at the capacity of
batteries in the last 10 years, it might paint a more informative picture.
Modern devices use Lithium ion or Lithium-polymer chemistries, as they feature
the highest energy density. While it may be potentially unnoticed due to the
higher energy consumption of modern devices being higher, any device shipped in
2012 would ship with an energy density that’s at least 30% lower than one made
today.
Research in battery tech leads to minor incremental changes
that add up over time to significant improvements. Recently, a company has shown that battery capacity
can be increased by changing the stacking geometry in a prismatic-cells used in
phones, computers and potentially electric cars.
Stacking layers of electrodes alternating is better than
rounding at the corners and the volumetric density increases by 13% due to less
wasted space [4].
Fast charging is also a concept that didn’t have widespread
adoption, as it was simply not viable and would damage batteries due to
internal heat build-up from the large currents employed. However, now, a smart
phone battery can be charged up to 6 times faster than 5 years ago [5].
Furthermore, the cost of lithium batteries has plummeted, as
a result of mass production, allowing for use in electric vehicles at ever more
affordable prices. Lithium-ion technology has dropped in price by 50% in the
last 5 years alone, and by a factor of 12 over a decade[6].
Batteries
will get much better
If the bar for batteries has been set higher, though demand
for longer lasting smart phones and the range anxiety of electric vehicle (EV)
drivers, what do the next 5 or 10 years hope to improve on and what type of
advancements can we hope to see?
Mitigating battery degradation
Battery capacity loss is a problem for all devices that utilise
batteries, however, the push for increased longevity has been mainly driven by
EV requirements. The reasoning behind this is that while phone batteries can be
replaced relatively affordably, an EV battery replacement can run in the tens
of thousands of pounds. One team of researchers managed to reduce dendritic
crystal growth by adding an inhibitory polymer into the electrolyte [7]. Others
have shown that tab cooling, as opposed to cooling on the sides provides a
further improvement in capacity, reaching up to 25% less degradation [8]. If
your EV battery holds charge better for longer your EV battery may last years
longer, and therefore make both range anxiety and the cost of ownership more
acceptable. Finally, new charging
methods are possibly one of the simplest ways to prolong the battery life,
combine this with effective colling, and better chemistry, batteries will last
longer.
Hybrid
batteries
Batteries employing conventional electrodes are limited in
their charge and discharge rates due to electrode resistance, which imposes
thermal problems and accelerated degradation. Addition of graphite to the battery electrodes
can reduce the resistance due to the higher electrode mobility of graphene.
Tests from Samsung show an improvement of about 45% in capacity.[9]
Solid state
Li-po cells
Every Lithium cell used in consumer applications uses
batteries that have the electrodes submerged in an ionic electrolyte, with a
separator in between, all contained by a pouch of a plastic sheath. Solid state
batteries do away with the liquid electrolyte and instead utilise a solid
electrolyte [10]. The potential for this to be a game changer is high,
considering that the capacity of such batteries can surpass current Lithium
cells by a factor of 50%. They also solve the issue of safety completely, as
they are unable to self-ignite, even with metal object puncturing the cells[11].
Novel
chemistry
While minor improvements have been able to improve batteries
thus far, to truly make a difference, transitioning away from conventional
chemistries might be inevitable. Lithium is a rare earth metal and the supply (which
is constrained) for it will not be able to keep up with demand indefinitely.
Considering that aluminium makes up 8% of the Earth’s crust, it is a suitable earth
abundant replacement material for lithium in our batteries. Furthermore, cells
using aluminium as the main electrode material have demonstrated resilience
with up to 10000 cycles in a lab environment. Lastly, aluminium has 3 electrons
in it’s valence shell, which gives it the potential to surpass even diesel in
its volumetric energy density by a factor of 2.7.
Conclusion
There are many improvements that can be further developed to
help make battery technology ‘invisible’, and there are many research labs all
around the globe that are working on new ways to construct batteries cheaper
and at larger energy densities. And the improvements that are to come will
allow us to be free and not have to worry about your charge indicator going to
0.
References:
[1] Battery
loss https://www.businessinsider.com/smartphone-batteries-are-only-meant-to-last-a-year-2015-10?r=US&IR=T#:~:text=According%20to%20Battery%20University%2C%20your,could%20reduce%2015%2D22%25.
[2] Battery
danger https://uk.pcmag.com/mobile-phones/135383/why-phones-explode-and-how-to-prevent-it-from-happening-to-you
[3] Bloomberg
figure https://cleantechnica.com/2020/02/19/bloombergnef-lithium-ion-battery-cell-densities-have-almost-tripled-since-2010/
[4] Stacked
cells
https://www.grepow.com/blog/cell-stacking-definition-grepow-battery-technology/
[5] Quick
charge: https://www.belkin.com/uk/resource-center/quick-charge/
[6] nature
figure https://www.nature.com/articles/d41586-021-02222-1
[7] Dendrite
inhibition https://cen.acs.org/energy/energy-storage-/Video-Battery-scientists-tackle-dendrite/97/i48
[8] Tab
cooling https://www.coolingzone.com/index.php?read=1294
[9] Graphene battery https://www.sammobile.com/news/samsung-phone-with-graphene-battery-coming-by-2021/
[10] https://thenextweb.com/news/why-solid-state-ev-batteries-are-better-than-lithium-ion-counterpart#:~:text=Higher%20energy%20density%20and%20faster,80%25%20charge%20within%2012%20minutes.
[11] Nail
test: https://www.youtube.com/watch?v=5rsafxxTkv4&t=4s&ab_channel=ProLogium%E8%BC%9D%E8%83%BD%E7%A7%91%E6%8A%80%E8%82%A1%E4%BB%BD%E6%9C%89%E9%99%90%E5%85%AC%E5%8F%B8
