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New silicon-sulfur battery built on 3D graphene shows excellent performance

Researchers at Beihang University in Beijing have developed a new Li-sulfur battery using honeycomb-like sulfur copolymer uniformly distributed onto 3D graphene (3D cpS-G) networks for a cathode material and a 3D lithiated Si-G network as anode.

In a paper published in the RSC journal Energy & Environmental Science, they reported that the full cell exhibits superior electrochemical performances in term of a high reversible capacity of 620 mAh g-1, ultrahigh energy density of 1147 Wh kg−1 (based on the total mass of cathode and anode), good high-rate capability and excellent cycle performance over 500 cycles (0.028% capacity loss per cycle).

Lithium-sulfur (Li-S) batteries are of great interest as next-generation energy storage solutions, especially for electric vehicles, due to their high energy density, low production cost and environmental friendliness.

A number of challenges—in both sulfur cathode and lithium-metal anode—are retarding their commercialization, however. On the cathode side, the inherent insulation of sulfur (5×10-30 S cm-1) and high solubility of polysulfide intermediates commonly cause large active-material loss and poor cycle performance.

A number of approaches have been taken to address these cathode issues, including embedding sulfur into various porous carbons such as activated carbons, macroporous, mesoporous and microporous carbons, generating sulfur-carbon hybrids with well-designed nanostructures.

While this has improved overall electric conductivity and inhibited loss of active materials, restricted pore volumes still limit the contents of sulfur and polysulfides.

Another cathode strategy has involved the use of sulfur copolymer; this has shown good inhibition of polysulfide dissolution, but needs improved electric conductivity.

On the anode side, the lithium-metal anode reacts with the commonly used organic electrolytes forms lithium dendrites during cycling, resulting in short life and sever safety issues.

Alloy-type anodes are potential alternatives because of similar voltage plateaus to lithium. A number of approaches have been proposed, including the use of Si nanowires and lithiated Si/SiOx nanospheres.

Thus, a new type of silicon-sulfur battery built from silicon-based anode and sulfur-based cathode is becoming one of next-generation Li-S batteries to overcome their severe cyclability and safety problems. However, the researches of emerging silicon-sulfur battery including the configurations, design and fabrication of appropriate and mutual matching anodes and cathodes are still in the infancy.

Herein, we develop a new configured lithiated silicon-sulfur battery with well-designed three-dimensional (3D) sulfur co- polymer cathode and lithiated silicon anode onto graphene networks. Our 3D sulfur copolymer cathode is synthesized through the thermal copolymerization of sulfur with 1, 3- diisopropenylbenzene (DIB) onto 3D graphene (3D G) network, which can significantly improve the electric conductivity of sulfur copolymer-based cathode. Remarkably enough, the re- sultant sulfur copolymer is anchored closely onto graphene skeleton in the state of separated and individual honeycombs with multi-sized pores, which not only facilitate the easy access of electrolyte, but also can efficiently restrain the dissolution of polysulfides and accommodate their large volume change during lithiation-delithiation processes. Coupled with our 3D lithiated silicon-graphene network as anode, a full lithiated silicon-sulfur battery with a high stability reversible capacity of 620 mAh g-1 based on the total mass of both cathode and anode, good high-rate capability, ultrahigh energy density (1147 Wh kg−1 based on the total mass of both cathode and anode) and excellent cycle performance (0.028% capacity loss per cycle over 500 cycles) is achieved, providing the best reported electrochemical performances for lithiated silicon-sulfur batteries to date.

—Li et al.

Li
Electrochemical performances of full lithiated silicon-sulfur battery built from 3D cpS-G networks cathode and 3D lithiated Si-G anode. a) Schematic illustration of a new configured lithiated silicon-sulfur battery onto 3D graphene networks. b) Selected voltage profiles of lithiated silicon-sulfur battery from 1st to 100th at 0.27 A g-1 based on the total mass of cathode and anode). c) Selected voltage profiles of lithiated silicon-sulfur battery at various current densities from 0.27 to 2.7 A g-1. d) Rate capabilities of Si-S battery and e) long cycle performances of full lithiated silicon-sulfur battery built on 3D graphene. Li et al. Click to enlarge.

Resources

  • Bin Li, Songmei Li, Jingjing Xu and Shubin Yang (2016) “A new configured lithiated silicon-sulfur battery built on 3D graphene with superior electrochemical performances” Energy Environ. Sci. doi: 10.1039/C6EE01019A

Comments

HarveyD

Tks DaveD.

You must be a real nice guy to stay as far away from as possible? We also have a few north of the border.

How did you catch it, or is it in your DNA?

Roger Pham

@E-P,

Good point. However, at 4C discharge, the battery capacity drops to 25%, hence implying that efficiency drops to 25%, implying a lot of internal resistance. The best that can be hoped for is 2C for a few seconds, though, for battery longevity, max discharge should be limited to 1C, which will then result in reasonable efficiency of around 75%.

With very high energy density, 1C for maximum discharge is good enough for a 100-kWh BEV capable of 100 kW of maximum power. Still good enough for a PHEV having 25 kWh of battery capacity capable of 25 kW of power, which means that engine start for occasional power boost will be necessary.

Though, it would not be competitive with high-power Tesla vehicle capable over 400 kW of maximum battery power.

Engineer-Poet

300 kg of a battery pack achieving 700 Wh/kg is 210 kWh.  A 4C surge discharge nets 840 kW.

Putting 800 kW to the ground in a 6000 lb vehicle yields a full 1 G of acceleration at 67 MPH.  That is, if the tires are capable of carrying that much thrust without slipping.  The sort of people who want cars with that kind of outrageous performance don't care about range.  C/1 is more than enough for an every-day vehicle, including tow vehicles.  A 6000 lb vehicle towing a 10,000 lb trailer up a 6% grade at 60 MPH, plus 150 lb of wind drag, takes ~120 kW.

Roger Pham

@E-P,

Again, good analysis and thanks for the example. To be precise, you don't really get 4C's worth of power, E-P. You are actually getting 3.5C to 2.5C, depending on the voltage, due to the drastic voltage drop as shown on the curve for the first 160mAh/g drained from the battery, from 2.1V down to 1.5V. After this, you will have to be content with 2C or even 1C as more energy is drained from the battery. The average C rating is around 3C for the first 160 mAh/g drained, then, it'll be downhill from then. So, you'll get 600 kW of power for the first 50 kWh of the pack, then you'll have to recharge to regain this power level.

Still, 3C on average for the initial 50kWh is still darn good, and can put out on average 600 kW max when 300 kg of battery is used. This may just "do it" to put BEV into the mainstream, if cost per kWh will be reasonable. The low-cost materials used is encouraging. If cost per kWh can be achieved around $100 per kWh pack level, then 200 kWh pack will cost around $20,000. A family car with 100-kWh pack will cost around $10,000 for the battery, with 150 kg of battery weight. Very good!

Andrew

There is not too many people drives 500 miles per day, even though the battery can last for 500 miles on a single charge, the driver has to take a rest.

Heat generated by charging and discharging might be more important to the EVs, safety is always the priority for car.

electric-car-insider.com

I doubt we'll see many cars with 100kWh batteries at $10k in the near term. The opportunity to sell many more 200 mile 60 kWh electrics with a margin on par with ICEs will be a more compelling business strategy.

As ZEV mandates ratchet up, automakers will need a volume EV strategy.

HarveyD

But he is soooo American and he realized the American dream with his pockets full of money and a very beautiful family.

A VP candidate, with opposite (complementary) public appeal, could fill in the gaps to get 50+% in November 2016.

The Northern Border may need a Berlin Wall to avoid what happened some 235 years ago?

Engineer-Poet

Don't worry about that, Harvey; there won't be a wall except to keep all your imported mudslimes out.  You can have all our BLM protestors and ethnic and gender grievance studies majors.  It'll give you a chance to learn to hate them too.

HarveyD

Your are correct. Many of our new 'migrants' will/do try to move south as soon as they are returned to good health (free), have received up to 18+ months of paid language courses and have managed to import as many family members as possible etc.

Since we are receiving 268,000+ migrants/year and rising to 300,000+/year soon, we wouldn't suffer if 500,000+ find their way south as long as we do not get as many (or more) the other way.

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