|Energy densities of different battery technologies. Source: ReVolt. Click to enlarge.|
ReVolt Technology Ltd, a technology company which has developed a rechargeable zinc-air battery (earlier post), and BASF have entered a joint-development agreement to speed the development and commercialization of ReVolt’s rechargeable zinc-air battery system. Revolt’s zinc-air technology offers up to three times the energy density on a volumetric basis and twice on a gravimetric basis of lithium-ion, according to the company.
Under the agreement, BASF will use its expertise in material science as well as electrochemistry to further advance the technology. BASF will supply key component materials and jointly developed subsystem elements necessary for the continued development and commercialization of ReVolt’s rechargeable zinc-air batteries.
In January 2009, RWE Innogy, the renewable power generation arm of Germany-based RWE Group, invested €5.5 million in ReVolt. The RWE investment was part of a €10 million Series B round that included current investors NorthZone Ventures (Sweden), SINTEF (Norway), Sofinnova Partners (France), TVM Capital (Germany), Verdane Capital (Norway) and Viking Venture (Norway).
ReVolt’s battery technology is a result of six years of research and development at SINTEF (the largest independent research institute in Scandinavia). Research on material combinations has addressed issues historically related to the metal-air technology; power, lifetime and rechargeability.
Metal-air electrochemical cells use an anode made from metals such as zinc (Zn) and a cathode made from a porous structure with catalytic properties for the oxygen reaction. An alkaline electrolyte maintains high ionic conductivity between the two electrodes. A separator between the anode and cathode prevents short circuits.
Discharging the metal-air cells entails the conversion of oxygen from the atmosphere to hydroxyl ions in the air electrode. The hydroxyl ions then migrate to the metal electrode, where they cause the metal contained in the electrode to oxidize. Charging of metal-air cells converts hydroxyl ions to oxygen in the air electrode, releasing electrons. On the metal electrode the metal oxides or ions are reduced to form the metal while electrons are consumed.
Rechargeability of zinc-air systems has been problematic, due to issues such as zinc dendrite formation, the battery drying out, and oxygen formation/reduction reversibility. ReVolt’s technology developments include placement of the zinc (microscopic localization) on the anode; humidity management in the cell; and a bi-functional air-electrode. In a bi-functional air electrode, both the oxygen reduction and oxygen evolution reactions occur.
A 100 percent-owned subsidiary of BASF SE, BASF Future Business was founded in April 2001 and focuses on chemistry-based new materials, technologies and system solutions. In June, BASF signed a world-wide licensing agreement with the US Department of Energy’s (DOE) Argonne National Laboratory to mass produce and market Argonne’s patented composite cathode materials to manufacturers of advanced lithium-ion batteries. BASF will conduct further lithium-ion battery material application development in its current Beachwood, Ohio facility. (Earlier post.)