Highly active nanostructured CoS2/CoS heterojunction electrocatalysts for aqueous polysulfide/iodide redox flow batteries

Dui Ma,Wenda Wu,Jiantao Zai,Xi Liu,Tsegaye Tadesse Tsega,Chen Shu,Bo Hu,Xuefeng Qian,Liwei Chen,T Leo Liu

doi:10.1038/s41467-019-11176-y

Abstract

Aqueous polysulfide/iodide redox flow batteries are attractive for scalable energy storage due to their high energy density and low cost. However, their energy efficiency and power density are usually limited by poor electrochemical kinetics of the redox reactions of polysulfide/iodide ions on graphite electrodes, which has become the main obstacle for their practical applications. Here, CoS2/CoS heterojunction nanoparticles with uneven charge distribution, which are synthesized in situ on graphite felt by a one-step solvothermal process, can significantly boost electrocatalytic activities of I−/I3− and S2−/Sx2− redox reactions by improving absorptivity of charged ions and promoting charge transfer. The polysulfide/iodide flow battery with the graphene felt-CoS2/CoS heterojunction can deliver a high energy efficiency of 84.5% at a current density of 10 mA cm−2, a power density of 86.2 mW cm−2 and a stable energy efficiency retention of 96% after approximately 1000 h of continuous operation.

Highlights

Aqueous polysulfide/iodide redox flow batteries are attractive for scalable energy storage due to their high energy density and low cost
All-vanadium redox flow batteries (RFBs) represent the current state-of-the-art, but their system price is near 4-fold higher than the price targets outlined by the Department of Energy of U.S, $10024
Power density and charge–discharge EE of a practical flow battery are mainly limited by the polarization derived from ohmic resistance, diffusion of active materials, and charge transfer overpotential at electrodes

Summary

Introduction

Aqueous polysulfide/iodide redox flow batteries are attractive for scalable energy storage due to their high energy density and low cost. Their energy efficiency and power density are usually limited by poor electrochemical kinetics of the redox reactions of polysulfide/iodide ions on graphite electrodes, which has become the main obstacle for their practical applications. The poor electrocatalytic activities for the redox reactions of I−/I3− and S2−/Sx2− on carbon material electrode usually restrict the EE and power density of SIFBs. power density and charge–discharge EE of a practical flow battery are mainly limited by the polarization derived from ohmic resistance, diffusion of active materials, and charge transfer overpotential at electrodes. Carbon materials are used as electrodes in most RFBs owing to their high electronic conductivity, good chemical stability, and economical cost[27]

Methods

Results

Conclusion