Metallic alloys containing thin, interconnected ‘snowflakes’ enhance the efficiency and safety of rechargeable batteries.

The tiny porous frameworks of zinc–antimony (ZnSb) nanoflakes are set to have a big impact on future hybrid vehicles and pocket-sized electronic devices. Qingyu Yan, Bee Yen Tay and co-workers from the Singapore Institute of Manufacturing Technology and Nanyang Technological University have deposited ZnSb nanostructures directly onto copper foil using a new technique to produce a material that could enhance the charge-storage capacity and safety of lithium-ion batteries.

Graphite is the anode of choice for most lithium batteries because it retains its structure quite well in the presence of lithium ions, giving the battery consistent charging behaviour. unfortunately, graphite has low charge-storage capacity, which limits the energy density of the battery. Pure lithium metal can also become intercalated into the graphite structure, which in extreme cases can cause the batteries to explode.

Incorporating materials with high theoretical charge-storage capacities, such as ZnSb, into the anodes of lithium-ion batteries could lead to thinner, lighter batteries that run at higher voltages. Unfortunately, antimony-based alloys can undergo destructive volume changes after repeated interactions with lithium ions, leading to early battery failure.

Lithium-ion battery from a laptop computer. © Kristoferb

Yan, Tay and their co-workers overcame ZnSb’s deformation problems by turning to the world of nanotechnology. By using a process that forces the rapid growth of crystals onto copper substrates, the team developed a method to produce ZnSb alloys containing honeycomb-like internal nanoscale pores. This ‘nanoflake’ structure enables the manipulation of ZnSb crystals into distinct nanowire and nanoparticle shapes.

After coating the ZnSb nanostructures with carbon to improve durability, the team found the ZnSb nanoflake structure to have a steady discharge capacity one-third higher than commercial batteries. They could also be recharged repeatedly without any structural changes. The intimate connection between the nanoflakes and the copper electrode also improved the battery’s charge-carrying efficiency to a remarkable 98 per cent.

“The fast, easy and cheap fabrication of ZnSb nanostructures without a template makes it possible to prepare anodes with improved electrochemical performance,” says Tay. “This system has the potential to form the basis for a new generation of lithium-ion batteries with higher energy densities.”

For further information contact:

Dr Bee Yen Tay
Singapore Institute of Manufacturing Technology
Agency for Science, Technology and Research
(A*STAR), Singapore
Email: bytay@SIMTech.a-star.edu.sg