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since the early 90s lithium-ion batteries have been the golden child in battery technology
powering everything from computers and phones to evs and even large-scale storage but as demand for
batteries increases so do the questions about the supply of raw materials battery performance levels
and affordability what if there was a battery that could take everything we love about
lithium-ion batteries and multiply it three times the energy density but at a fraction of the price
that's what the lithium sulfur battery promises for decades this promising battery technology has
remained just out of reach the very chemistry that makes it so incredible also makes it virtually
unusable at least it used to be but thanks to a completely accidental discovery this incredible
technology may finally be close at hand so what's with all the hype surrounding lithium
sulfur batteries compared to lithium sulfur is an electrochemically active material that can accept
up to two electrons per atom at around 2.1 volts compared to lithium ion lithium-ion cathodes have
reached a capacity of around 200 milliamp hours and energy densities around 800 watt hours per
kilogram a lithium sulfur battery which uses sulfur as the cathode the negatively charged
electrode and lithium as the anode the positive end can reach theoretical energy densities upwards
of 2600 watt hours per kilogram that's over three times the energy density of lithium-ion battery
so what does this mean in terms of running your electronics if you would replace the lithium-ion
battery in your computer right now with a lithium-sulfur battery of the same weight
you could run the computer for over three times as long or you could achieve the same runtime
with a battery that weighs three times less imagine what that could do for an electric
vehicle today's top performing evs using lithium ion batteries have ranges that top out around 500
miles now imagine replacing that lithium ion battery with a lithium sulfur battery
now a car with a battery that weighs exactly the same could travel 1500 miles on a single charge
and those are just the conservative figures some estimates say the lithium sulfur batteries could
increase energy densities by up to 500 percent that could mean a range of up to 2500 miles
you could drive from san diego to seattle and back on a single charge using sulfur as the cathode
material could also help reduce the cost of batteries while also helping alleviate some of the
impact on various materials compared to lithium sulfur is a far more earth abundant material
almost as abundant as iron today so many devices rely on lithium and while it's not exactly a rare
material finding other suitable substitutes will only help us down the road as battery technology
becomes more and more necessary not only for personal electronics and evs but for grid storage
as well sulfur would also eliminate the use of other materials like manganese nickel and cobalt
elements that carry both global supply concerns as well as humanitarian issues but the most
convincing reason to utilize sulfur is that it is significantly less expensive than just about
every other material currently used for batteries today cobalt for instance is considered a rare
metal typically priced around 75 000 per metric ton but since the 2020 pandemic wreaked havoc on
the global supply chain prices have skyrocketed by more than 50 percent in 2021. lithium has also
seen price inflation due to increasing short-term production from 7 000 per metric ton to nearly 40
000 but then there's sulfur and even though it too has seen prices climb the same time period
nearly 47 the cost is still dirt cheap coming in around 382 dollars per metric ton for comparison
for the price of one ton of cobalt you could buy nearly 200 tons of sulfur but as we mentioned
earlier while lithium sulfur batteries hold so much promise there's a reason why we haven't seen
them in production but thanks to a groundbreaking accidental scientific discovery that might
all change as great as future evs will be it's important to remember the evs are already super
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that support this show so the reality of lithium sulfur batteries may finally be close at hand
thanks to a complete accident made by researchers at drexel university's college of engineering
dr viba carla and her team were actually testing different methods of overcoming some of the
drawbacks often associated with lithium sulfur batteries as we mentioned earlier the reaction
between the positively charged lithium ions in the sulfur cathode comes with all those amazing
benefits we listed before but that same reaction has some unfortunate side effects during the
charge discharge process sulfur goes through a series of structural changes resulting in a
formation of chemical deposits called polysulfides these deposits form tree-like structures called
dendrites that branch up from lithium anode degrading both the anode and the electrolyte
the medium that carries lithium back and forth between the anode and the cathode
effectively killing the battery after a relatively small number of cycles
while a standard lithium iron battery remains usable for around 1 000 to 2000 charge cycles
lithium sulfur batteries in a laboratory condition max out at a fraction of that amount meaning in a
practical situation lithium sulfur batteries would be dead only after a year or two of use
one strategy often used to counter the shuttling effect has been to use ether electrolytes that
can dissolve the polysulfides but these types of electrolytes come with their own baggage namely
that they can be expensive making them less practical for large scale applications
they can also be incredibly volatile and unstable not to mention the amount needed to actually solve
the shuttling problem could hamper the energy density of the battery which sort of defeats
the entire purpose dr carla's solution was to find a way to make the batteries function with a more
industrial friendly carbonate electrolyte the kind used in most lithium ion batteries the experiment
essentially involved attempting to constrain the sulfur in a carbon nanofiber effectively trapping
the polysulfide so that they wouldn't react with the electrolyte at all but the experiment failed
or at least it didn't do what dr carla thought it would but what her and her team discovered was
something completely unexpected when mixed with the carbon nanofiber the sulfide stabilized into
an incredibly rare form called monoclinic gamma sulfur a form of sulfur that has a rectangular
prism form made of eight sulfur atoms packed together the thing is this type of sulfur
doesn't typically stay stable at room temperature in fact it's usually only created in labs at
extremely high temperatures and only appears in nature in extreme environments like oil wells
according to raul pai a doctoral student in the department of chemical and biological engineering
and co-author of the research in the last century there have only been a handful of studies that
produced monoclinic gamma sulfur and has only been made stable for about 20 or 30 minutes at most but
here in this laboratory setting the team was able to create it completely by accident so what's so
significant about this discovery it turns out that this particular crystallized form of sulfur
doesn't react with the carbonate electrolyte the way other forms of sulfur would effectively
eliminating the polysulfide and shuttling effect along with them what does this mean for
battery performance when the team put the carbon nanofibers into a lithium sulfur battery with a
carbon electrolyte they were able to cycle it for a total of 4 000 times without losing performance
the equivalent of 10 years of use not only that but the battery they tested had three times the
capacity of today's lithium ion batteries so that's it right problem solved let's go ahead
and swap all the theme on batteries for lithium sulfur well not quite see as with most accidental
discoveries the team that has to figure out why the experiment turned out the way it did how did
this phase of sulfur appear can they replicate it and can they ensure that it would stay that way
so suffice it to say further research is still needed before we can start seeing these batteries
for sale but the research doesn't stop there the team is using this discovery to further research
into other lithium free battery technologies like sodium sulfur batteries so while this accidental
discovery hasn't fully made lithium sulfur batteries a reality just yet they have brought
us significantly closer than anything before it so like with most batteries we talked about on
this channel this is one of those where it's not quite ready for prime time but as you can imagine
the ramifications of battery like this is really important every electric vehicle manufacturer
is struggling with supplies battery material supply chains are just difficult and it's really
what keeps companies from making more evs so a breakthrough battery like this could be hugely
significant not to mention the better performance and longer life but just by being diversified
and having more various elements come into the battery supply chain that would just mean all the
difference for larger scale battery storage and electric vehicle proliferation all right so if you
want to see more videos about breakthrough battery technologies check out this playlist over here
i'm ricky youtube davinci thank you so much for watching we'll catch you guys next week