A rotatable cathode with tunable steric hindrance for high-performance aluminum organic batteries

Abstract

For the first time, a rotatable structural cathode (calix[4]quinone) with low/adjusted steric hindrance was proposed in RABs to overcome confinement from large-size active-ions, which achieved one of the highest energy densities in RABs.

Abstract

Rechargeable aluminum batteries (RABs) with uniquely high energy-to-price ratios are promising energy storage systems. However, owing to the large-size active ions ( e.g. AlCl ₄ ⁻ and [AlCl ₂(urea) ₂] ⁺) in state-of-the-art ionic-liquid RABs, the discharge–charge process usually encounters severe steric hindrance on electrodes, resulting in insufficient active-site utilization with limited practical capacity, and sluggish ion-diffusion kinetics with inferior rate-performance. Herein, to overcome these intrinsic confinements from the large-size active ions, we proposed, for the first time, a structure-rotatable cathode (quinone-based calix[4]quinone (C4Q)) for RABs with highly reduced steric hindrance, which is further verified via density functional theory (DFT) simulations. The newly applied C4Q cathode achieves one of the highest energy densities (480 W h kg ⁻¹ at 0.1 A g ⁻¹), enhanced rate capacity (81 mA h g ⁻¹ at 1.0 A g ⁻¹), and long-term stability (102 mA h g ⁻¹ at 0.2 A g ⁻¹ after 500 cycles) in RABs. Furthermore, the reaction mechanism of this rotatable cathode is revealed in detail via a series of characterization studies and corresponding DFT simulations. Overall, this new family of rotational organic materials will provide a new direction for promising high-performance RABs.