A safe and efficient lithiated silicon-sulfur battery enabled by a bi-functional composite interlayer

Abstract

Replacing lithium metal in a lithium-sulfur battery with lithiated silicon can enhance safety and reversibility while maintaining the high energy density. However, fabricating lithiated silicon, while protecting it against lithium polysulfides, is difficult. In this work, we design and prepare a protected lithium/carbon nanofiber composite interlayer for simultaneous lithiation and protection of the silicon anode. The interlayer is fabricated via two steps of reactions, first by reacting antimony trifluoride-modified carbon nanofibers with molten lithium, and then by coating it for a tightly anchored solid electrolyte layer on lithium. The interlayer can be directly inserted between a separator and a silicon anode during battery assembly to lithiate and protect the anode, which enables the stable operation of a lithiated silicon/sulfur battery of a practical loading (4.0 mg cm-2 for both silicon and sulfur) at 2.5 mA cm-2 for 200 cycles, with capacity retention up to 94%. This work demonstrates how we can achieve a durable full battery via a scalable structural design strategy, which could be extended for use in other types of (lithium, sodium, potassium)-ion/sulfur batteries.