Corset-like solid electrolyte interface for fast charging of silicon wire anodes

The most challenging tasks in today's batteries are the need for fast charging and large energy densities for longer lifetimes. Micro-structured silicon microwire anodes show a nine-fold increase in gravimetric capacity over standard graphite batteries. The anodes exhibit an areal capacity of 4.25 mAhcm−2 with a specific capacity of 3150 mAhg−1. The high specific capacity implies a 400% volume expansion of the Si wires. This paper demonstrates that by modifying and adapting the electrolyte composition a charging speed of 5 C (12 min charging time) can be reached completely maintaining the area and gravimetric capacity of the silicon anodes. Detailed analysis of the charge transfer processes across the solid electrolyte interface into the silicon wires reveals highly relevant mechanisms for this stable performance. A well-established solvent candidate, like propylene carbonate, which was rated not at all suitable for graphite electrodes, is very promising and advancing fast for pure silicon anodes. This addition into the electrolyte allows modifying the mechanical properties of the SEI layer in oder to support revery individual silicon wire to buffer the inevitable volume expansion.