Evaluation of Hybrid Anode Usability in Lithium Polysulfide Flow Batteries

Abstract

The scalability of lithium‐sulfur batteries can be improved by implementing them as lithium polysulfide flow batteries (LPSFBs). However, a low specific capacity and rapid capacity fading are observed in these flow batteries. We discovered that this deficiency can be addressed by using a hybrid anode. The hybrid anode consists of a lithiated graphite felt and a Li metal. The former serves as the buffer in lithiation and delithiation to shift most of the parasitic reactions that normally occur on Li to lithiated graphite to result in an improved protection of the Li surface. Specifically, in a 0.4 m lithium polysulfide catholyte, a LPSFB with an activated hybrid anode could be cycled with a high Coulombic efficiency (≈100 %) and high energy efficiency (≈79.5 %) to deliver a high specific discharge capacity of 532.5 mAh g−1 at 1 mA cm−2 current density, of which 87.4 % of the capacity could be retained after 40 cycles. This represents a significant improvement in the cycle stability and sulfur utility of LPSFBs.