A light-weight free-standing graphene foam-based interlayer towards improved Li-S cells

Abstract

A light-weight and free-standing graphene foam interlayer placed between sulfur cathode and separator is investigated to improve the electrochemical performance of lithium-sulfur batteries. The highly conductive and light-weight porous graphene foam not only increases the electron pathway of cathode, but also adsorbs the dissolved high-order lithium polysulfides during cycles, thus the loss of active materials is greatly avoided with only minimum mass addition approximately 0.3 mg cm−2 on cathodic side. Additionally, the atomic layer deposition method is applied to deposit the zinc oxide nano-scale coating on graphene foam interlayer in order to chemically trap the polysulfides with minimized deterioration on conductivity of graphene foam. Among all the graphene foam, graphene foam@zinc oxide and graphene foam/graphene foam@zinc oxide interlayers, the graphene foam/graphene foam@zinc oxide exhibits the best electrochemical performance, delivering an initial specific capacity of 1051 mAh g−1 at 0.5 C and retaining a reversible capacity of 672 mAh g−1 after 100 cycles, while the cell without interlayer only shows 346 mAh g−1. These results demonstrate the strategy of including a zinc oxide modified graphene foam interlayer as an effective light-weight interlayer for improving Li-S cell performance.