Stable copper anode enabled by an ionic conducting sulfurized interphase

Abstract

Lithium metal is one of the most promising anodes for non-aqueous battery because of its high capacity and low potential, and recently, lithium-free anode has been proposed which can further increase the real electrode capacity by utilizing lithium (Li) deposition and dissolution on copper (Cu) current collector. However, either Li or Li-free anode has been much plagued by the solid electrolyte interphase (SEI) issues, dendrite growth and dead Li formation induced by slower Li+-diffusion across the interphase and/or difficult Li nucleation on heterogeneous substrate. In this work, constructing an artificial copper sulfide (CuS) layer on Cu was proposed to address these issues. Copper sulfide has been loaded on Cu substrate through a facile vapor-deposition method. The extra layer reduced the contact between electrolyte and electrode. Additionally, a favorable interphase was generated by the in-situ conversion of CuS, which was composed of sub-micron lithium sulfide (Li2S) and Cu particles. The former optimized the SEI composition structure and improved the Li+ diffusion pathway, and the latter decreased the real local current density. With these assistances, dense and uniform Li deposition on Cu was achieved. The Li|S-Cu cell realized 300 times stable cycling and the Li@S-Cu|LiFePO4 full cell could well maintain the capacity as long as 200 cycles. This work provides an alternative strategy to regulate the electrode/electrolyte interface and sheds more lights on the Li deposition/dissolution reaction kinetics.