|Simplified cycle life of a sustainable Li-ion battery. Click to enlarge.|
Researchers at Université de Picardie Jules Verne in France have developed a new renewable organic electrode material—the oxocarbon salt Li2C6O6—for lithium-ion batteries. The material demonstrates high capacity—better than some conventional inorganic electrode materials—and good thermal stability, although a relatively poor cycle life.
While research on organic electrodes has been underway for 25 years, earlier attempts were characterized by low capacities or other limitations. The new oxocarbon salt starts from a renewable resource (i.e. myo-inositol) and shows a reversible capacity as high as 580 mAhg-1 for a specific energy density of about 1,300 Whkg-1 of active material.
|Top. Specific energy density of the organic Li2C6O6-based electrode compared with inorganic LiCoO2 and LiFePO4. Bottom. Volumetric energy density. Click to enlarge.|
A report on the work, which demonstrates a pathway to a sustainable Li-ion chemistry, is the cover article for the 21 April issue of ChemSusChem.
Li-ion batteries presently operate using inorganic insertion compounds for the electrode materials, which may present issues in terms of materials lifecycle costs in the long term with rapidly scaling applications. The researchers cite a recent integrated lifecycle assessment that indicates that 72 kg/kWh of CO2 is emitted for the production of Li-ion batteries, materials and recycling.
It is now becoming mandatory to decrease the consumption of non-renewable resources, the amount of waste produced as well as energy consumption. Herein, we suggest the possibility of a paradigm shift to electrode materials that have the lowest possible life-cycle cost, that is, high-performance organic matter coming from biomass.
Oxocarbons are compounds in which all (or nearly all) of the carbon atoms are bonded to carbonyl or enolic oxygen atoms or their hydrated or deprotonated equivalents. The researchers used myo-Inositol, which is available from renewable resources (CO2-harvesting plants) as a precursor for the synthesis of the oxocarbon. No toxic solvents are required during the processing steps.
The oxocarbon salt contains carbonyl groups as redox centres and can electrochemically react with four Li ions per formula unit.
The bright results of the high capacity of the LixC6O6 electrode together with its good temperature stability (220°C) and the absence of runaway reactions in the presence of electrolytes are somewhat tarnished by its relatively poor cycle life, although our results provide important new insights which could give rise to a paradigm shift in present concepts of improving Li-ion batteries that are based on both chemical substitution of inorganic compounds and decreasing particle sizes.
The use of modern green chemistry concepts, starting from a renewable natural precursor for the synthesis of electroactive molecules, brings new dimensions in terms of materials lifecycle costs and sustainability in general, thus opening new research avenues.
Haiyan Chen, Michel Armand, Dr., Gilles Demailly, Prof., Franck Dolhem, Dr., Philippe Poizot, Dr., Jean-Marie Tarascon, Prof.; From Biomass to a Renewable LiXC6O6 Organic Electrode for Sustainable Li-Ion Batteries; ChemSusChem 4/2008 DOI: 10.1002/cssc.200890008