Nanocomposites: Turbocharger for lithium batteries

Nanocomposites: Turbocharger for lithium batteries

Technology News |
By Christoph Hammerschmidt

The storage capacity and power density of lithium-ion batteries are far superior to those of other rechargeable battery systems. But still, smartphone batteries last only one day, electric cars need hours to recharge. Scientists are therefore working on ways to further improve the energy densities and charging rates of the all-round batteries. “An important factor is the anode material,” explains Dina Fattakhova-Rohlfing from the Institute for Energy and Climate Research (IEK-1) at the Jülich Research Centre.

Anodes based on tin dioxide can in principle achieve much higher specific capacities – i.e. store more energy – than carbon anodes currently used. “They have the ability to absorb more lithium ions”, explains Fattakhova-Rohlfing. “However, pure tin oxide shows very poor cycle stability – the storage capacity of the batteries decreases continuously and they can only be recharged a few times. With each charging and discharging cycle, the volume of the anode changes, causing it to crumble.”

One way to tackle this problem is with so-called hybrid materials or nanocomposites – composites containing nanoparticles. The scientists have succeeded in developing a material made of tin oxide nanoparticles enriched with antimony on a base layer of graphene. The graphene base serves for structural stability and simultaneously contributes to the conductivity of the material. The tin oxide particles have a size of less than three nanometers and are “grown” directly onto the graphene. The small size of the particles and their good contact with the graphene layer also improves the tolerance to volume changes – the lithium cell becomes more stable and lasts longer.

The enrichment of nanoparticles with antimony should make the material extremely conductive. This makes the anode much faster, so that it can store more than one and a half times more energy in just one minute than would be possible with conventional graphite anodes – and with the usual charging time of one hour even three times as much.

Up to now, such high energy densities could only be achieved at low charging rates. Faster charging cycles always led to a rapid reduction in capacity. The newly developed antimony-doped anodes, on the other hand, retain 77 percent of their original capacity even after 1000 cycles.

Fattakhova-Rohlfing makes another argument for the new nanocomposite anodes: they can be produced easily and cost-effectively. “And the concepts applied can also be used to design other anode materials for lithium-ion batteries,” explains the scientist. This could clear the way for the production of lithium-ion batteries with a significantly increased energy density and very short charging time.


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