CONICET | Buscador de Institutos y Recursos Humanos

In this work we used the Nuclear Magnetic Resonance technique (NMR) to study the structural changes that occur in the silicon-graphite anodes, during the electrochemical charge-discharge cycles, of a lithium-ion battery.One of the main problems to be resolved when we are linking together the renewable energy sources with the electric distribution systems, is the delivery potency variation through time. Therefore, a successful strategy is to complement the renewable sources with batteries that, once charged, are able to deliver a constant potency to the net. Nowadays, the most promising products are those of the electrochemical kind, like the recharged lithium-ion batteries.Silicon anodes are a particularly attractive alternative to those of graphite due to their high specific capacity. Nevertheless, this unusual capacity is associated with an electrode volume change, during the charge-discharge processes, up to 300%. This expansion produces fractures and a fast and pronounced capacity loss, which could lead to the battery dead. Attempts to solve the troubles caused by the volumetric changes of silicon have included the use of binders and other additives as well as limitations over the applied voltage at which the anode is charged and discharged, reducing the battery capacity.The NMR technique is useful to study of the anode during the charge-discharge process. The NMR spectra depends on the lithium nuclei local environment, allowing to obtain information about the state of charge of a battery. The lithium nuclei (7Li and 6Li) are typically, but not exclusively, used as probes due to the fact that the Li+ ions are directly involved in the electrochemical processes occurring in a lithium-ion battery. This method allows to determine the species removed during the charge process and how the local structure changes over the extended charge cycle.