Silk could be new 'green' material for next-generation batteries

March 11, 2015, American Chemical Society
Silk could be new 'green' material for next-generation batteries

Lithium-ion batteries have enabled many of today's electronics, from portable gadgets to electric cars. But much to the frustration of consumers, none of these batteries last long without a recharge. Now scientists report in the journal ACS Nano the development of a new, "green" way to boost the performance of these batteries—with a material derived from silk.

Chuanbao Cao and colleagues note that carbon is a key component in commercial Li-ion energy storage devices including batteries and supercapacitors. Most commonly, graphite fills that role, but it has a limited energy capacity. To improve the energy storage, manufacturers are looking for an alternative material to replace graphite. Cao's team wanted to see if they could develop such a material using a sustainable source.

The researchers found a way to process natural silk to create carbon-based nanosheets that could potentially be used in . Their material stores five times more lithium than graphite can—a capacity that is critical to improving battery performance. It also worked for over 10,000 cycles with only a 9 percent loss in stability.

The researchers successfully incorporated their material in prototype batteries and supercapacitors in a one-step method that could easily be scaled up, the researchers note.

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More information: Hierarchical Porous Nitrogen-Doped Carbon Nanosheets Derived from Silk for Ultrahigh-Capacity Battery Anodes and Supercapacitors ACS Nano, Article ASAP. DOI: 10.1021/nn506394r

Hierarchical porous nitrogen-doped carbon (HPNC) nanosheets (NS) have been prepared via simultaneous activation and graphitization of biomass-derived natural silk. The as-obtained HPNC-NS show favorable features for electrochemical energy storage such as high specific surface area (SBET: 2494 m2/g), high volume of hierarchical pores (2.28 cm3/g), nanosheet structures, rich N-doping (4.7%), and defects. With respect to the multiple synergistic effects of these features, a lithium-ion battery anode and a two-electrode-based supercapacitor have been prepared. A reversible lithium storage capacity of 1865 mA h/g has been reported, which is the highest for N-doped carbon anode materials to the best of our knowledge. The HPNC-NS supercapacitor's electrode in ionic liquid electrolytes exhibit a capacitance of 242 F/g and energy density of 102 W h/kg (48 W h/L), with high cycling life stability (9% loss after 10 000 cycles). Thus, a high-performance Li-ion battery and supercapacitors were successfully assembled for the same electrode material, which was obtained through a one-step and facile large-scale synthesis route. It is promising for next-generation hybrid energy storage and renewable delivery devices.

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1 / 5 (2) Mar 11, 2015
Amazing development but, seems pretty much on the cards, panelising the layers of super-caps into vehicle (& home) structural panels may be a worthwhile pursuit subject to various risk assessment criteria...

The confluence of the various graphite/graphene technologies has immense diversity already only shortly after its started...

Well done, more for fruitful thought please :-)
not rated yet Mar 11, 2015
It also worked for over 10,000 cycles with only a 9 percent loss in stability.

Notice: this applies to the supercapacitor.

I see no mention of the cycle life for the lithium battery configuration.

In supercapacitor use 10,000 cycles isn't all that impressive, considering that these components must often be rated for 50,000 hours of operation at elevated temperatures and may be subjected to billions of cycles during their lifetime in devices like power supplies.

An example use case is a power buffer for a car audio amplifier. Blast the subwoofer at 60 cycles a second, each pulse causing a partial cycle on the capacitor, and your 10,000 cycles runs out before the CD ends.

The other issue is the supply and demand of silk. A synthetic material would be preferrable to something that has to be extruded out of the bottoms of larvae.
not rated yet Mar 11, 2015

Supercapacitors (except those with polymer electrodes) can potentially support more than one million charge/discharge cycles without substantial capacity drops or internal resistance increases.

So, much ado about nothing really.

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