(Invited) Synergy of Carbonyl and Azo Chemistries for Wide-Temperature-Range Rechargeable Aluminum Organic Batteries

Abstract

Developing low-cost, sustainable, and all-climate energy storage devices as alternatives to Li-ion batteries (LIBs) is critical for the global application of electric vehicles, grid-scale electrical energy storages. Among various emerging battery systems beyond LIBs, rechargeable aluminum organic batteries (RAOBs) stand out because of the high theoretical capacity, low cost, abundance, high sustainability, and high safety of Al and organic resources. However, the large ion size of Al complex ions, such as AlCl4 -, AlCl2 + and AlCl2+, or the strong Coulombic interaction between Al3+ ions and active materials, as well as the high diffusion energy barrier of Al3+ ion, lead to poor cyclic stability and sluggish reaction kinetics. Moreover, the reaction mechanism, interphase structure, and the impact of multi-functional groups in redox-active organic materials to the electrochemical performance of RAOBs remains elusive. To address these challenges, we designed and synthesized a redox-active polymer bearing carbonyl and azo groups as the cathode to achieve high-performance and wide-temperature-range RAOBs. The polymeric cathode exhibits a high reversible specific capacity, superior cyclic stability, fast charging capability, and a wide operation temperature range (-40oC to 100oC). X-ray photoelectron spectroscopy (XPS), pair distribution function (PDF) analysis, and soft X-ray absorption near edge structure (XANES) were employed to gain fundamental insight into the carbonyl and azo chemistries in RAOBs, as well as the cathode electrolyte interphase (CEI) structure. We demonstrated a step-by-step alumination/de-alumination reaction for carbonyl and azo groups in the polymer cathode and unravel a Al2O3- and AlN-rich CEI, which is critical for the impressive performance of RAOBs.