Temperature effects on SEI formation and cyclability of Si nanoflake powder anode in the presence of SEI-forming additives

Silicon nanoflake powder (Si LeafPowder (R), Si-LP) used as an anode material for lithium-ion batteries has demonstrated superior cycle performance at 30 degrees C in an ethylene-carbonate-based electrolyte solution because its characteristic thin-film-based structure resists pulverization. However, capacity fading was accelerated at 60 degrees C owing to enhanced decomposition of the electrolyte solution and growth of a solid electrolyte interface (SEI), which leads to loss of the electronic contact between Si-LP particles. The SEI-forming additives vinylene carbonate (VC), fluoroethylene carbonate (FEC), and difluoroethylene carbonate improved the capacity retention and Coulombic efficiency at 30 degrees C. Although VC is the most effective additive at 60 degrees C, the discharge capacity was decreased dramatically at - 5 degrees C owing to poor ionic and electronic conductivity of the SEI layer formed from the VC-added electrolyte solution. The added FEC produced better performance in a wide temperature range of - 5 to 60 degrees C because the SEI layer formed in the FEC-added electrolyte solution had higher ionic and electronic conductivity than that formed from VC, even at - 5 degrees C. To obtain Si anodes with high discharge capacity and long cycle life, an appropriate choice of SEI-forming additive taking into account the operating temperature is important. (C) 2016 Elsevier Ltd. All rights reserved.