cnrs I international w 20 | Focus magazine Better Batteries Most electric cars need recharging after 150-200 km. In terms of power grid, the storage capacity is only 1%. These two figures illustrate the enormous challenge of storing electricity. How can electric cars be given enough autonomy to cover long distances on a single charge? How can Included more of the electrical power produced by conventional as well as renewable—and therefore intermittent—technologies (wind, solar) be stored in order to inject it back into the network during peak demand? Today’s batteries do not have the capacity to meet these challenges. “The objective is to increase their energy density while guaranteeing their operational safety and lowering their cost, in accordance with the principles of sustainable development,” explains Jean- Marie Tarascon of the LRCS1 in Amiens. This seemingly impossible equation has not deterred researchers in the many laboratories of France’s network on electrochemical energy storage (RS2E),2 formed in 2010 to bring together all players in the field, including industrial companies (see box). 04 Production of lithium-ion car batteries at the Johnson Controls- Saft factory in Nersac (France). HIGH-CAPA CITY MAT ERIALS Today’s electric vehicles are powered by lithium-ion batteries (which contain lithium in ionized form). To improve their performance, the RS2E is investi- gating two potential solutions. The first consists in boosting the capacity of battery materials or in developing new ones, like fluorosulfates and hydroxo- sulfates, which make chemical bonds more prone to produce ions, thus increasing the energy density. Some of these materials, studied at the LRCS and the IMN3 are also “greener”—derived from the biomass or produced using enzymes or bacteria and therefore completely recyclable. The second possibility for increasing battery performance is to explore alternative technologies. In lithium-air battery, for example, atmospheric oxygen reacts with the lithium. “This solution is very effective in theory, but raises complex problems,” Tarascon explains, “such as the need to find better catalysts, which are 04 © P. PSaïla ENERGY DENSITY. The quantity of energy stored per unit volume. A dedic ated french ne twork The RS2E (French network on electrochemical energy storage) comprises 14 laboratories (10 of which make up the Store-Ex consortium), 3 public industrial and commercial institutions (CEA , Ineris, IFP Énergies nouvelles), and several industrial companies (Renault, PSA , EADS -Astrium, Rhodia, Saft, ED F, Saint-Gobain, Arkema, Solvionic, Acuwatt). online : > www.energie-rs2e.com
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