The ever-increasing energy demands of modern societies, with the massive use of portable devices, the widespread utilization of renewable energies and the irruption of the electric vehicle is boosting the demand of energy storage devices with higher power, higher energy density and improved stability. Among the next emerging energy storage devices, metal–air batteries are focusing intense research and development and extensive interests in the energy field due to their high theoretical energy density and potential low cost with high level of safety
Particularly, the use of zinc as anode in metal air-batteries represents a safe, environmentally friendly and cheap option to store and deliver electrical energy for both portable and stationary applications.
Zinc–air batteries can be classified into primary (non-rechargeable), and secondary (electrically rechargeable). Research on primary zinc–air batteries is well consolidated since many years ago with very cheap and optimized products. On the other hand, research on the Zn-air rechargeable technology still requires further efforts to overcome materials science challenges and electrochemical issues mainly related to charge and discharge processes.
A zinc–air secondary battery is composed of three main components: a zinc anode, an alkaline electrolyte and an air electrode (cathode). An air electrode is typically formed by a current collector, a gas diffusion layer, an active catalyst layer and a membrane that allows the entrance of oxygen and avoids the leakage of electrolyte. Oxygen diffuses through the membrane passing the gas diffusion layer and the catalyst layer on the cathode allows the oxygen reduction reaction (ORR) to hydroxide ions with the electrons obtained from the electrochemical oxidation of the zinc at the anode. During charge, oxygen evolution reaction (OER) takes part at the air electrode and oxygen diffuses out of the positive electrode, whereas zinc is deposited at the negative electrode. Taking into account this configuration, an air electrode with a bifunctional catalyst with dual activity in both ORR and OER must be used for a Zn-air rechargeable battery.
Within several possibilities, the use of nanocomposites based on doped-carbon materials as bifunctional catalysts in ORR and OER is a promising path to improve efficiency of the battery. In this field, Gnanomat develops metal oxide-graphene nanocomposites to be used as bifunctional electrocatalysts providing a substantial improved performance and stability during charge and discharge: Moreover, Gnanomat offers a versatile design and synthesis of electrocatalysts based on environmentally friendly elements. The addition of metal oxide nanoparticle synthesized from Gnanomat IP confers high power and cycling stability to the zinc-air battery.