A Pan-European group of researchers have shown that a pinch of salt can drastically improve the performance of lithium-ion batteries.
Queen Mary University of London, University of Cambridge and Max Planck Institute for Solid State Research, found that adding salt to the inside of a supermolecular sponge and then baking it at a high temperature transformed the sponge into a carbon-based structure.
According to the researchers, the salt reacted with the sponge in special ways and turned it from a homogeneous mass to an intricate structure with fibres, struts, pillars and webs.
This kind of 3D hierarchically organised carbon structure has proven very difficult to grow in a laboratory but is crucial in providing unimpeded ion transport to active sites in a battery.
The team has so far confirmed that the use of these materials in Lithium-ion batteries not only enables the batteries to be charged-up rapidly, but also at one of the highest capacities.
Due to their intricate architecture the researchers have termed these structures ‘nano-diatoms’, and believe they could also be used in energy storage and conversion, for example as electrocatalysts for hydrogen production.
The supermolecular sponge used in the study is also known as a metal organic framework (MOF) material. These MOFs are attractive, molecularly designed porous materials with many promising applications such as gas storage and separation.
The retention of high surface area after carbonisation – or baking at a high temperature – makes them interesting as electrode materials for batteries.
However, so far carbonising MOFs has preserved the structure of the initial particles like that of a dense carbon foam.
Now by adding salts to these MOF sponges and carbonising them, the researchers have discovered a series of carbon-based materials with multiple levels of hierarchy.
University of Cambridge’s Dr R Vasant Kumar said: “This work pushes the use of the MOFs to a new level. The strategy for structuring carbon materials could be important not only in energy storage but also in energy conversion, and sensing.”
Image and content: Dr Jingwei Hou/Queen Mary University of London