Lithium-sulfur batteries, the future after Tesla’s Gigafactory?

You leave your 100% Renewable Energy powered home, get into your Electric Vehicle and drive a thousand miles without worrying about charging its batteries. This futuristic clean energy landscape is closer and closer thanks to researchers like Zhi Wei Seh, who is helping develop lithium-sulfur batteries, with 3 to 5 times higher energy density than Tesla’s Gigafactory ones.

 

Tesla's Gigafactory
Tesla

 

If you have been following us for a while, you will be familiar with the EmTech Asia. Like the CEOs of start-ups like Grey Orange and its robots to operate warehouses, AIME and its platform capable to predict dengue outbreaks or REX Computing and its revolutionary chips, I also met Zhi Wei Seh at that event in Singapore. He was one of the ten Innovators Under 35 chosen to present a three-minute elevator pitch there.

With a PhD in Materials Science and Engineering by Stanford University, Zhi Wei Seh is a Scientist at the Institute of Materials Research and Engineering (IMRE) at the Agency for Science, Technology and Research (A*STAR), in Singapore. He is designing novel nanostructures for lithium-sulfur batteries, which can store 3 to 5 times more energy than the lithium-ion batteries today.

In the long-run, hopefully every home and industry in the world will be powered with Renewable Energy from the grid.

Because of the Renewable Energy intermittency (it depends on intermittent natural resources like wind or solar power), you need to pair it up with battery systems. The increase in its energy density will help improve the deployment and utilization of Renewable Energy and help decarbonize the energy landscape achieving a more secure energy future.

Apart from these huge electric grids, these batteries might also be implemented in Electric Vehicles or in our daily life devices, like mobile phones or laptops.”

 

Zhi Wei Seh at EmTech Asia
EmTech Asia

 

Beyond Elon Musk and Tesla’s vision

Last November, Elon Musk (Tesla’s CEO) claimed to have the cheapest cells in the market, while being also the best ones, allowing you to drive from San Francisco to Los Angeles (400 miles) without recharging.

Early this year, Tesla’s Gigafactory started battery mass-production. According to Tesla’s plans, this huge factory located in Nevada (United States), and still under construction, will double the world’s lithium ion battery production by 2018. Is there room for another technology?

“Elon Musk is trying to achieve economies of scale so he can manufacture the lithium-ion batteries at a very low cost, bringing down the cost of Electric Vehicles. I admire him for this part. As he pointed out, they will be able to drive from San Francisco to Los Angeles, but we are looking at something greater than that, a 3 to 5 times further increase in the driving distance.

I see it more like a transition. The new material batteries are not mature yet, so in the next 5 years lithium-ion battery technology will still be dominant. As we better understand the fundamentals of the lithium-sulfur batteries, we will be able to improve their performance and there will be a slow transition into this new technology.”

 
I asked Zhi Wei Seh about another Tesla product, the Powerwall. The company claims that this product can supply the energy for a four-room house for 24 hours, using the stored energy generated from PV’s during day time, meaning that it is already possible to own a home 100% powered with Renewable Energy.

“Not every home can afford to have a microgrid (solar PV + energy storage), so we still need to depend on the centralized electric grid. I am not talking about powering single homes with Renewable Energy, but the entire electric grid itself.

Now, because we use fossil fuels, there’s no need for energy storage in our grids. But when Renewable Energy is more widely used, we will need big, high capacity, long-lasting batteries that can, for example, store the solar power during daytime and release it at night, to be transmitted from the grid to other homes and industries.”

 

Replacing lithium-ion batteries with lithium-sulfur ones

“After having worked for about 10 years on lithium-ion batteries design, we are very close to the theoretical limit of the energy density they can achieve. Now, it is only possible to improve it by developing new battery chemistries drastically different from the traditional ones. We need to replace the materials in there for others with even higher charge capacity.

Also in terms of cost, lithium-sulfur batteries have an advantage as well, because sulfur is cheap and very abundant. In fact, it is a by-product of the petroleum industry. They have tons of it, and don’t know what to do with it.”

 
In the short video below, Zhi Wei Seh explains what a lithium-sulfur battery is and what the difference between them and lithium-ion batteries:

 

 

Cheaper and better batteries than those we are using today. What is stopping us from getting there?

“Lithium-sulfur batteries typically suffer from fast capacity decay and short cycle life because the sulfur intermediates leak out into the electrolyte during the operation of the battery. Sulfur expands about 80% when the battery is charging and discharging, causing the shell to crack.

To address this challenge, we have developed a yolk-shell structure, which involves encapsulating the sulfur electrode in a titanium dioxide shell to prevent these sulfur intermediates from leaking out while engineering an internal void space into the shell to allow the sulfur to expand during the battery operation.

With this yolk-shell structure and a coin cell configuration (like the button cells used in watches), we have achieved 1000 charge-discharge cycles maintaining 70% of the original capacity. In terms of energy density, with this configuration we can achieve three times that of lithium-ion batteries, going from 420Wh/kg to 1200 Wh/kg.”

 

Yolk-shell strucutre for lihium-sulfur batteries

 

“There are still some technological issues that need to be addressed, like electronic conductivity problems on the positive electrode side (the sulfur side) when trying to scale it up, or some safety issues in the negative electrode side (a lithium metal), like the formation of very sharp structures during the battery charging and discharging that might hit the positive electrode causing a short-circuit.”

 

It sounds like a promising landscape, but when can we expect to see these batteries in the market?

“There’s a company called Sion Power (stands for sulfur ion) that already has done some lithium-sulfur battery prototypes. I believe that this kind of lithium-sulfur technology will be widespread in five years from now.”

 

Want to see the full three-minutes elevator pitch that Zhi Wei Seh delivered in the EmTech Asia? Click here!

 

Electrocatalysts as the perfect complement to batteries

At this point, you may be thinking that the possibilities the future lithium-sulfur batteries will bring are quite exciting. Well, here comes the real science-fiction! Are you ready?

Apart from his work in batteries, Zhi Wei Seh is also developing electrocatalysts to convert simple molecules in the atmosphere into fuels!

“They are more or less complimentary. For example, we can use batteries for powering Electric Vehicles today, but it is very hard to electrify trucks, marine, rail or air transport. So, the way we can do that is to have a sustainable way of producing fuels and chemicals we can use for these heavy duty vehicles.

The way we envision is to convert molecules in the atmosphere like water and carbon dioxide into useful compounds. Water can be used for water splitting, producing hydrogen that can be used as a clean fuel to power this kind of transport.

Carbon dioxide, which is a greenhouse gas, can also be potentially converted into fuels like metanol or ethanol. Because these fuels have been converted from carbon dioxide, it is overall a carbon neutral cycle.

To achieve this vision we need some catalyst that can do this conversion fast enough. Right now this process is highly inefficient. We are also developing a catalyst to potentially speed up these reactions, making them more efficient and sustainably producing these fuels.”

 

Electrocatalysts

 

Wow! Not only driving EV non-stop and living in 100% Renewable Energy powered homes, but also powering trains and planes with air! Can’t wait to see that!

Thank you Zhi Wei Seh for sharing your work and vision of the future with us! It feels good to know that there are people like you working to make of the world a better place for all of us to live in!


If you wish to keep updated about the work innovators and entrepreneurs are doing, drop your e-mail below and we’ll notify you monthly!

 

Borja Bonet

Hi! I'm Borja, and I'm so glad to be a part of this project and to be sharing ideas and experiences with all of you! Let's do it together! Welcome to Ambitious Tracks!

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