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Will Batteries Power The World? | The Limits Of Lithium-ion

This video was made possible by Anker – more
on that later. Over the last twenty years, a slew of ever-lighter,
ever-more-powerful rechargeable batteries has enabled the rise of smartphones, miniature
high definition cameras, drones, commercially competitive electric cars, wireless headphones,
and so on. It seems like we’re moving towards a future
where the entire planet is battery-powered, but there are two big factors that will come
into play: 1) how light and energy dense we can make batteries, and 2) whether we’ll
even be able to physically manufacture enough batteries. This video covers part 1 of this question,
and Brian of Real Engineering is covering part 2 – we’ll link to his video at the
end. Ok, so batteries have been getting better
and better, and nowadays, they can store over twice as much energy per kilogram as in the
1990s , which means they’re half the weight for the same energy stored. Hence all the drones and smart phones. So what’s the limit to this trend? Batteries are, in principle, fairly simple:
take two partially dissolved metals, one whose atoms want to dissolve more and give up electrons,
and one whose atoms want to deposit back on the solid bit but need spare electrons to
do so. When you put these two together connected
with a wire or some other conductor , they’ll satisfy each others’ wants, either dissolving
more or depositing more, and sending the electrons to each other along the wire. Voilá: electricity! And if you force electricity backwards through
the wire they’ll reverse their dissolving and depositing, otherwise known as “re-charging”. The intrinsic limits to how lightweight batteries
can be are imposed by two factors: the weight of the two materials you use, and how much
energy they give off per electron traded. So you want the lightest materials that produce
the most energy per electron. Metals from the left side of the periodic
table, like lithium, sodium and beryllium, really want to lose electrons, while atoms
from the right side like fluorine, oxygen, and sulfur really want electrons. And atoms close to the top are lighter weight,
so we can just slap together lithium and fluorine and make a perfect battery, right? Unfortunately, no – lithium and fluorine
are way too reactive – one of the only well-documented practical uses of a lithium fluorine reaction
I could find was incredibly powerful and dangerous rocket fuel. In practice, the electrochemistry of batteries
is incredibly complicated, and requires combining metals that work well together chemically,
electrically, and controllably at normal temperatures and pressures . For example, oxygen is a gas,
sulfur is a horrible conductor, and sodium needs to be molten – challenges to using
any of them to make batteries. The current standard for lightweight, rechargeable
and commercially safe batteries uses lithium and graphite on one side, with a variety of
options for the other side, often cobalt oxide . Lithium atoms are what either dissolve or
deposit in order to transfer electrons, hence the name “lithium ion”, while the other
materials are dead weight along for the ride – I mean, they play important chemical
roles, but they greatly increase the weight-per-electron transferred. So how much lighter will batteries get? Theoretical calculations put the minimum possible
weight for lithium ion batteries at around half what they currently are .
A lighter candidate currently being developed is the lithium-sulfur battery , which has
a similar amount energy-per-electron as lithium-ion batteries, but lithium and sulfur are lighter
than lithium and cobalt, oxygen and carbon , so a battery with equivalent capacity can
in principle weigh around a third as much .
Even better, lithium-oxygen batteries , while still an incredibly far-off technology, are
theoretically four times lighter than lithium sulfur batteries. But that’s pretty close to the limit for
chemical-reaction-based batteries – there aren’t really any materials that give off
more energy per electron for a given weight than lithium on the dissolving side and fluorine
on the depositing side , and a lithium-fluorine battery – as dangerous and impossible as
it is – is limited to only be about 10% lighter than a lithium-oxygen battery .
So the theoretical lower limit for batteries, period, is about 5% of current weights. But that’s an incredible long-shot, everything-works-out,
perfect world scenario. More likely is that we end up combining pretty-good
batteries with supercapacitors, fuel cells, hydropower and other mechanical energy storage
types, and airplanes will probably always have to use some sort of hydrocarbon fuel. Or maybe we’ll finally figure out fusion. Ok, so here’s an example of the amazing
battery technology we have available today : this battery pack is crazy small and light
– it’s basically eight of these with some clever circuitry – and it has enough
energy to charge a smartphone 10 times, which is equivalent to running this LED lightbulb
for 10 hours. The makers of this ridiculous battery pack,
Anker, are sponsoring this video and also running a ridiculous contest where they’re
giving away ten prizes of two thousand dollars plus one of their battery packs – they’re
asking for video submissions about a time that running out of power was awkward or unpleasant
– you know, like how Apollo 13 almost ran out of batteries, or how I only made it halfway
through mowing the lawn last week. You can find out more about Anker’s batteries
and the contest by going to the links in the video description. And one aspect of batteries I haven’t mentioned
at all yet is power delivery – aka, how quickly they can charge your devices – this battery
pack is smart enough to detect what you’ve got plugged in in order to optimize charging
time. And of course don’t forget to check out
Brian’s video about whether or not it’s even possible to make enough batteries to
power the planet.
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