Sodium ion batteries are receiving increased interest due to concerns over the long-term sustainability of the lithium ion batteries that are used in everything from cellphones to solar power storage and electric vehicles. The low cost and abundance of sodium make it an interesting candidate to replace lithium, which is driving research into creating new materials for use in sodium ion batteries.

Yuxi Xu, Fudan University, Shanghai, China, Imran Shakir, King Saud University, Riyadh, Saudi Arabia, and colleagues have developed potential cathode systems for sodium batteries. The materials are composites of graphene aerogels and metal cyanide. The team designed an easy and versatile spatially-confined Ostwald ripening strategy to synthesize 3D graphene wrapped metal cyanide aerogels. Incorporation of the cyanide into the porous conductive framework of the graphene alleviates the problem of poor electronic conductivity seen in bulk cyanides.

A series of composites based on the well-known cyanide pigment Prussian Blue, Fe₄[Fe(CN)₆]₃·H₂O, were synthesized and tested. The materials displayed highly enhanced electrochemical properties, especially in current density (up to 2500 mA/g) and cycle life (90 % capacity retention after 1000 cycles). The researchers believe that the synthetic strategy could be extended to other graphene-wrapped coordination polymer aerogels as high-performance electrodes for a wide range of applications.

• One Versatile Route to Three-Dimensional Graphene Wrapped Metal Cyanide Aerogels for Enhanced Sodium Ion Storage,
  Fanxing Bu, Xiaoxiang Feng, Tiancai Jiang, Imran Shakir, Yuxi Xu,
  Chem. Eur. J. 2017.
  DOI: 10.1002/chem.201700742