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New Battery Breakthrough

Just wondering if Tesla is aware of this as it could dramatically improve baterry performance if it works...

Cheap, strong lithium-ion battery developed at USC

By Robert Perkins
February 12, 2013
Researchers at USC have developed a new lithium-ion battery design that uses porous silicon nanoparticles in place of the traditional graphite anodes to provide superior performance.

The new batteries — which could be used in anything from cellphones to hybrid cars — hold three times as much energy as comparable graphite-based designs and recharge within 10 minutes. The design, currently under a provisional patent, could be commercially available within two to three years.

“It’s an exciting research. It opens the door for the design of the next generation lithium-ion batteries,” said Chongwu Zhou, professor at the USC Viterbi School of Engineering, who led the team that developed the battery.

Zhou worked with USC graduate students Mingyuan Ge, Jiepeng Rong, Xin Fang and Anyi Zhang, as well as Yunhao Lu of Zhejiang University in China. Their research was published in Nano Research in January.

Researchers have long attempted to use silicon, which is cheap and has a high potential capacity, in battery anodes. (Anodes are where current flows into a battery, while cathodes are where current flows out.)

The problem has been that previous silicon anode designs, which were basically tiny plates of the material, broke down from repeated swelling and shrinking during charging/discharging cycles and quickly became useless.

Last year, Zhou’s team experimented with porous silicon nanowires that are less than 100 nanometers in diameter and just a few microns long.

The tiny pores on the nanowires allowed the silicon to expand and contract without breaking while simultaneously increasing the surface area, which in turn allows lithium ions to diffuse in and out of the battery more quickly, improving performance.

Though the batteries functioned well, the nanowires are difficult to manufacture en masse. To solve the problem, Zhou’s team took commercially available nanoparticles — tiny silicon spheres — and etched them with the same pores as the nanowires. The particles function similarly and can be made in any quantity desired.

Though the silicon nanoparticle batteries currently last for just 200 recharge cycles (compared to an average of 500 for graphite-based designs), the team’s older silicon nanowire-based design lasted for up to 2,000 cycles, which was reported in Nano Lett last April.

Further development of the nanoparticle design should boost the battery’s lifespan, Zhou said.

“The easy method we use may generate real impact on battery applications in the near future,” Zhou said.

Future research by the group will focus on finding a new cathode material with a high capacity that will pair well with the porous silicon nanowires and/or porous silicon nanoparticles to create a completely redesigned battery.

So many people out there working on this stuff...its great because although current technology can make EV's for the masses possible now...these breakthoughs and many others make the evenutal transition to the EV inevitable.

I would also add that when the market is ready to deliver these new technologies...Tesla will be perfectly positioned to take advantage of them.

I'd like to add some thought and fact about LI batteries and their potential.

Anode: potential improvements are mentioned above. Si, Sn, and nanostructures will help to bring up mAh/g numbers. But take into account that the anode only a fraction of the weight of battery, so a doubling in specific anode capacity wouldn't result in a doubling of the cells specific energy/energy densisty. Some is true for the Kathode, but the cathode is a little heavier, so improvements here have a little bit bit effect, like improvements on the anode-side. This is why a large portion of electrode research is focussing on the cathode

Cathode: So called 5V chemistries (like Lithium Cobald Phosphates or NMC Phosphates) have a huge potential, as they will give the cell a higher nominal voltage and also have slightly higher specific capacity. The problem here is to have a stable electrolyte, which can withstand higher potentials.

In the last years LI cells improved by 7% p.a. But this doesn't mean it will continue that why. Faster improvments can be made, but there is a certain physical/chemical/technical and also ecomic reasonable limit to what can be achieved.

Personally I see a potential for maybe 30-40% improvment potential on specific energy, some 100% improvment potential on cycle life and specific power. Nanotechnology and improvments in manufacturing will help the last two numbers the most.

I can be off by a lot, but to my todays knowledge this would be my best guess, which can be done in the next 5 years.

There is also structural improvement. Look up "banding", developed by MIT (I believe), which multiplies speed and ease of movement of ions in the electrolyte to the terminals.


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