• Universitat de València

Nanocomposites are becoming materials of great interest for energy storage applications due to the properties provided by their various components. Among the potential nanocomposites being synthesised, those from layered double hydroxides (LDH) are attracting particular attention, especially carbon and metal oxide nanocomposites, for their potential applications in electrochemical devices such as supercapacitors. However, most of the new materials investigated are commercially unfeasible because of their very high cost and the manufacturing complexity.

Researchers at the Universitat de València have designed new low-cost nanocomposites with excellent supercapacitance and giant magnetoresistance (GMR) properties. Nanocomposites are obtained by a simple, one-step, low-temperature process from highly available and low-cost materials such as LDH. Nanocomposites consist of magnetic nanoparticles (NPs) of a metal alloy (e.g. FeNi3) and a nanostructured carbon matrix.

The NPs can be easily removed in a next step, by acid leaching of the hybrid composite, allowing the isolation of diverse carbon nanoforms, including carbon nanobeads and multi-layered carbon nanotubes. This methodology opens the door to the synthesis of these new, low-cost and more environmentally friendly forms of carbon.

The developed nanocomposites are applicable in any type of device requiring materials with supercapacitance properties. Supercapacitors are mainly used in energy storage: electrical power supply stabilisation, auxiliary vehicle support units, battery replacement in some specific applications, etc. On the other hand, due to the GMR properties, these materials are also useful for spintronics applications, such as hard disk drive read heads and magnetic sensors. Finally, the resulting carbon nanoforms have a wide range of potential applications in materials science, electronics and nanotechnology.

The developed nanocomposites have the following advantages:

• Low cost: they are obtained by a one-step chemical process with a single precursor, at low temperature, and with accessible, non-polluting and inexpensive materials.

• Supercapacitance: they have much higher specific capacitance values than those obtained with commercial nanostructured carbon electrodes.

• Good cyclability: the cyclability tests carried out predict good prospects in terms of electrochemical and mechanical stability.

In addition to their advantages as supercapacitors, nanocomposites have other advantages associated with the following additional properties:

• Giant magnetoresistance: this property is observed at room temperature and without the application of high magnetic fields.

• Carbon nanoform source: starting from nanocomposites, a mixture of carbon nanoforms consisting of carbon nanobeads and multi-layered carbon nanotubes can be obtained.

• Patent granted