Subnano-sized silicon anode via crystal growth inhibition mechanism and its application in a prototype battery pack

Abstract

Silicon-based anodes are a promising alternative to the graphite anodes that are widely used in today's commercial batteries. Here the authors report a synthesis route for silicon anodes consisting of subnanometre-sized particles and demonstrate their use in an unusual large-scale battery pack system. Due to the large volume variation of high-capacity alloy-based anodes during cycling, it is desirable to use small anode particles for an extended battery cycle life. However, it is still challenging to realize subnano-sized particles (<1 nm). Here we show a growth inhibition mechanism that prevents continuous enlargement of size immediately after nucleation during chemical vapour deposition. The growth inhibition is successfully applied to the synthesis of silicon, thereby yielding subnano-sized (<1 nm) silicon embedded in a highly stable dual matrix composed of carbon and silicon carbide. Ethylene not only functions as a silicon growth inhibitor, thereby slowing the growth of nucleated silicon via Si-C bond formation, but also acts as a source to create the dual matrix. The subnano-sized silicon anode enhances the cycling stability (Coulombic efficiency reaching 99.96% over 50 cycles). Finally, the practical application of the fabricated energy storage system (103.2 kWh) containing 110 Ah full-cells with 91% capacity retention for 2,875 cycles and a calendar life of 97.6% for 1 year is demonstrated.