Diphenyl ditelluride as a low-potential and fast-kinetics anolyte for nonaqueous redox flow battery applications

Abstract

Developing low-potential, fast-kinetics and highly concentrated anolyte materials is one of the major challenges for nonaqueous redox flow batteries (NRFBs). Organosulfides exhibit promising potentials for NRFBs owing to their high solubility and structure diversity. However, they suffer from poor reaction kinetics and intermediate reversible potential, leading to poor roundtrip efficiency and low full cell voltage. Herein, we report diphenyl ditelluride (PDTe) as a low-potential and fast-kinetics anolyte candidate. The reversible potential of PDTe (average 1.97 V vs. Li/Li+) is lower than that of its sulfur counterpart PDS (2.25 V), which offers higher full cell voltages. We demonstrated a Li/2.5 M PDTe half-cell with a high volumetric capacity (128 Ah L−1PDTe), and high coulombic and energy efficiency (>99.5% and 84.1%) over 100 cycles. A Li/0.1 M PDTe flow cell achieved a stable long cycling over 260 cycles (38 days) at 1.5 mA cm−2. Coupling with lithium iodide (LiI) catholyte, the PDTe/LiI full cells demonstrated stable cycling over 120 cycles. Density functional theory calculation reveals that the cleavage of ditelluride bond requires a much lower bond dissociation energy than that of disulfide bond, which significantly reduces battery voltage hysteresis (by 429 mV). This study demonstrates the promising potential of organotellurides as anolytes for energy storage applications.