PERFORMANCE OF SILICON NEGATIVE ELECTRODES WITH CNTS IN LI-ION BATTERY SYSTEMS

Silicon is capable of delivering a high theoretical specific capacity of 4200 mAh g-1 order of magnitude higher than that of the state-of-the-art graphite based negative electrodes for lithium-ion batteries. Using silicon- containing negative electrodes can increase significantly the energy density of the Li - -ion batteries. However, the poor cycle life of silicon electrodes, caused by the large volume changes and consequent strains formation during cycling, limits the practical importance of silicon electrodes. As one of the essential components, the choice of the right polymeric binder for the composite electrodes is important to the performance and durability of lithium-ion batteries as it keeps the integrity of electrodes. For silicon anodes, the binder used is critically important, due to the morphological instability of Li-Si electrodes during lithiation-delithiation cycling. When using micrometric silicon as the active mass for Li-Si anodes, there are severe problems of mechanical and electronic integrity of this active mass. The relatively low conductivity of large Si particles must be taken under consideration and can be compensated by conductive additives such as CNTs. In this work, we demonstrate that electrodes consisting of micrometric silicon particles mixed with commercially available sodium alginate binder together with CNTs as an additive are able to maintain a high specific capacity. We discuss aspects of binders, choice of electrolyte solutions and the practical options of Li-Si anodes in advanced Li ion batteries.