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  • MAREN: So if you watched our previous episode on how batteries work,

  • you'll know that batteries are complicated.

  • They come in all shapes, sizes, charge capabilities,

  • and we use them in everything.

  • And if there's one battery technology that sets the gold standard,

  • it's the lithium-ion battery.

  • These batteries are one of the only types

  • to pack powerful energy storage

  • in a small and lightweight design.

  • So, when designing battery technologies for the future,

  • the challenge is to improve upon the advantages

  • that the lithium-ion battery already has.

  • Because even though lithium-ion batteries

  • currently dominate the global battery market,

  • there are quite a few things about them that could be improved,

  • like power output, energy capacity,

  • cost, lifespan, and safety.

  • Now some of the most promising designs

  • for giving lithium-ion battery technology a boost

  • are the lithium-silicon battery,

  • the lithium-sulfur battery,

  • solid-state lithium-ion batteries

  • and one that's a common nation of approaches.

  • And changing out the materials used

  • to make anodes, cathodes and electrolytes

  • is exactly what scientists have been doing.

  • But what is it gonna take for one of these

  • to become the new battery of the future?

  • It's important to note that a simple change

  • in a battery's design can significantly affect

  • its voltage and storage capacity.

  • Here I've made a really simple homemade battery

  • with 14 cells using an ice cube tray,

  • steel screws, copper wire, a couple electrical leads,

  • and this voltmeter.

  • And the way this works is that each little ice cube tray

  • is its own battery cell.

  • So you've got the copper acting like the cathode.

  • It's gaining electrons.

  • The steel is acting as the anode.

  • It's losing electrons.

  • And the salt water is acting as my electrolyte,

  • allowing that flow of charges.

  • Now, when I hook it up to the voltmeter,

  • you can see I am reading a voltage of around 200 millivolts.

  • Now, what I'm interested in is what would happen

  • if we changed out the electrolyte solution

  • to the, say, vinegar.

  • Lemon juice.

  • So all these sorts of things can make a significant impact

  • on the voltage and the storage capacity of the battery.

  • MAREN: First up, silicon anode batteries.

  • Remember that anodes are the negative electrode within a call?

  • Well, like we talked about in the last episode,

  • the current most popular anode material

  • in lithium-ion cells is graphite.

  • This is because graphite's structure helps keep

  • those lithium ions efficiently stored in the anode.

  • But there is a maximum amount of lithium-ions

  • that can be stored in the anode,

  • and that determines the cell's capacity.

  • And as it turns out,

  • silicon does a much better job than graphite

  • at absorbing and holding lithium-ions.

  • And this means batteries can be made smaller,

  • more energy-efficient, and cheaper.

  • But, of course, this does all come with a catch.

  • Silicon anodes have a tendency to dramatically expand

  • when encountering lithium during charging.

  • And those anodes also then shrink

  • when the battery discharges.

  • And this repeated expansion and contraction

  • shortens the lifespan of the battery,

  • and ultimately, its usefulness.

  • But researchers like those at Enovix,

  • are aiming to fix this problem.

  • We don't eliminate anode expansion and contraction,

  • but we do control them.

  • Propendent 3D cell architecture

  • enables us to integrate

  • a very thin stainless steel constraint

  • into our battery design.

  • This applies a uniform force around the battery

  • to constrain the silicon expansion within the cell.

  • during the charging cycles and during discharge.

  • MAREN: While some researchers have set their sights on the anode,

  • others are experimenting with the cathode

  • with one innovation being lithium sulfur cells.

  • Lithium on its own is a very volatile substance.

  • It reacts to air, it reacts to water.

  • So what the OXIS scientists have done

  • is taken sulfur as a non-conductive, very cheap material.

  • and used the sulfur to act as a fire retardant

  • around lithium metal,

  • so that if air or water impacts lithium metal,

  • thermal runaway, fire, explosion, doesn't take place.

  • Sulfur cathodes, like their silicon anode counterparts,

  • can absorb more lithium ions

  • than the typical cobalt-based cathodes.

  • offering a reduced battery cost

  • with increased energy density and improved safety

  • compared to lithium-ion batteries.

  • HUW: Because one of the key factors

  • of lithium sulfur

  • is that it is 50 to 60% lighter than lithium-ion.

  • Now, if you take a bus with a very large battery,

  • if you can replace that technology with lithium-sulfur

  • and you reduce the weight and still

  • extend the distance covered,

  • then you have a major breakthrough

  • in the renewable transportation systems.

  • But lithium-sulfur cells are still not quite perfect

  • because they face the challenge

  • of lithium-polysulfide formation,

  • or what's known as the polysulfide shuttle.

  • The sulfur electrode also expands and contracts

  • as it cycles, which results in a loss of battery efficiency

  • and power and energy density.

  • But what if the answer isn't in the anode or the cathode?

  • What about the electrolyte?

  • Well, that's where solid state batteries come in.

  • Solid state electrolytes have been around for a while

  • and have recently caught on

  • as a contender for future batteries

  • because of their promise of improved safety.

  • But solid state polymers can better withstand extreme conditions.

  • So when heated, they behave like liquids,

  • but they can operate without the danger of bursting into flames.

  • Some researchers believe that solid state batteries

  • could even give electric vehicles

  • over 500 miles of range.

  • And if we really let our imaginations run wild,

  • using solid state batteries in solar powered vehicles

  • like the ones that compete in the World Solar Challenge

  • could potentially lead to even longer ranges.

  • Now, what's the downside to these solid state batteries?

  • Well, unlike liquid electrolytes,

  • they can't stay in contact

  • with every bit of the electrodes all the time.

  • And this makes it harder for the ions

  • to move between electrodes

  • and create that flow of electricity that we need.

  • But what if we were able to combine

  • a few of these innovations that we've already talked about?

  • We could now make a transition

  • from liquid electrolyte to solid state lithium sulfur.

  • And I'm talking about removing the diesel trucks, diesel buses,

  • the lead based fuel that our aircraft consume.

  • These are the biggest pollutants that we've got on the planet,

  • and solid state is certainly the phenomenon

  • that will render those achievements more realistic.

  • MAREN: So OXIS Energy is currently not in the solar car market,

  • but is instead focusing on aerospace,

  • marine vessels, and electric vehicles.

  • They're close to achieving an energy density

  • of 500 watt-hours per kilogram

  • with their battery,

  • and have already set a new target

  • of 600 watt-hours per kilogram.

  • Essentially, that means a battery like this in the future

  • could be capable of powering an electric car

  • for 1,000 kilometers on a single charge.

  • By comparison, Tesla's Panasonic lithium-ion battery cells,

  • which are currently the most commercially advanced,

  • are about half as energy dense.

  • So all of the battery innovations we've covered

  • are definitely impressive.

  • But if we want more solar vehicles on the roads,

  • we're gonna need a powerful battery storage system

  • with high energy density, high efficiency,

  • and the ability to last long on the road, rain or shine,

  • because currently, none of the options on the market

  • or even in development totally do the job.

  • That's why it's important to have events like the World Solar Challenge,

  • 'cause when creating a vehicle like this,

  • you're pushing technology to its limit.

MAREN: So if you watched our previous episode on how batteries work,

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What is the Battery of the Future?

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    林宜悉 posted on 2021/01/06
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