Toward constructing high-specific-energy sulfur suspension catholyte for lithium flow battery

Abstract

Semi-solid suspension electrode is a new approach to develop flow batteries for large-scale energy storage technology, understanding the evaluation behaviors of rheological properties and their relationship with electrochemical performance is of great importance in constructing high-specific-energy suspension electrodes. Herein, sulfur suspension catholyte was employed to investigate the effects of combination mode and content of conductive additive, active material concentration, surfactant on the rheology and electrochemistry of suspension electrodes. The suspension using sulfur and Ketjenblack (KB) codeposition composite (S@KBCC) exhibited lower viscosity and higher sulfur utilization compare with mechanical mixture (S/KB) and sulfur impregnated KB (S-KB). The conductive percolation networks formed when KB content was 0.5 g L−1 in suspension, increasing KB content improved electronic conductivity and sulfur utilization, but leaded to increased viscosity and stress; conductivity, sulfur utilization and viscosity reached the inflection points by modulating KB content. The effects of surfactant Triton X-100 were evaluated in regulating rheological and electrochemical properties, sulfur catholyte with high specific energy of 602 Wh L−1 and power density of 56.6 mW cm−2 was achieved in flow modes. This work proposed the procedures as guides to construct high-energy-density sulfur suspension catholyte, and also offers a reference for other semi-solid electrodes.