A low-cost and dendrite-free rechargeable aluminium-ion battery with superior performance

Abstract

Aqueous aluminium-ion rechargeable batteries (AAIBs) have attracted lots of attention due to their high theoretical capacity, high volumetric energy density and low price. However, not many aqueous full batteries have been developed successfully due to the low standard reduction potential of Al³⁺ (−1.68 V vs. standard hydrogen electrode, lower than H⁺) in aqueous solutions. In this study, we highlight an inexpensive “water-in-salt” aqueous electrolyte (AlCl₃·6H₂O) that can expand the electrochemical stability window of AAIBs to roughly 4 V. We propose a full aluminum-ion battery (AIB) using such an aqueous electrolyte. Its capacity reached 165 mA h g⁻¹ at 500 mA g⁻¹ (3C), and it exhibited over 95% coulombic efficiency consistently over 1000 cycles. Moreover, the aqueous Al-ion battery we developed is low-cost (the electrolyte is roughly 2% the cost of traditional electrolyte of Al-ion batteries) and dendrite-free in the negative electrode throughout the tests.