Producing Sustainable, Cost-Effective Aluminum-Sulfur Batteries Through a Triple-Function Cathode Design and Anion Charge Carriers

Overview

Rechargeable batteries are powering the rise in plug-in electric vehicles and intermittent renewable energy storage/transport/utilization in the electricity grid. With a goal of increasing energy density and reducing production cost, the aluminum-sulfur (Al-S) battery has attracted tremendous interest due to its high theoretical energy density (2981 WhL-1) and the earth-abundant aluminum/sulfur feedstock. However, the lifetime and commercialization of current Al-Sbattery technology is limited by 1) intrinsic low conductivity of sulfur cathode, 2) polysulfide shuttle effect, and 3) sluggish conversion and transfer of aluminum species in electrolytes. The overall objectives of this project were to (1) design and synthesize triple-function additives of sulfur cathode to mitigate shuttling effect, (2) develop novel chloroaluminate ionic liquid electrolytes with an overall ionic conductivity higher than 5 mS/cm, and (3) elucidate microscopic redox chemistry, transport and charge storage mechanism of chloroaluminate anions (AlCl4- and Al2Cl7-), and their stability challenges in ionic liquid electrolyte-based sustainable Al-Sbatteries with high performance. These goals were achieved by studying the roles (physical confinement, chemical adsorption, and catalytic effect) of sulfur cathode additives, compositionally optimized chloroaluminate ionic liquid electrolytes (AlCl3 to EMIC ratios: 1.1:1, 1.3:1, 1.5:1) via in situ Raman spectroscopy, NMR, and electron microscopy techniques. This study showed that the synergistic effect of triple-function additives in sulfur cathode can dramatically mitigate the polysulfides shuttle and promote the lifespan (1000 cycles) of Al-Sbatteries. These results can be transformative in potential applications to electric vehicles and the electricity grid.