On the challenge of developing scalable and sustainable Aluminum-Ion batteries: From Active to Passive Materials

The ongoing energy revolution has spurred interest in new battery types with innovative cell chemistries over the last five to ten years. This shift is partially driven by the increasing gap between the demand and supply of essential resources like lithium, nickel, and cobalt, resulting in volatile prices, particularly for lithium.1, 2 Consequently, the search for affordable, reusable, and safe sustainable cell chemistries has led to the development of rechargeable sodium-ion batteries (SIBs). Other promising chemistries, such as zinc-ion batteries (ZIBs) and potassium-ion batteries (KIBs), are still in the research phase.
A notable advancement is the aluminum-graphite dual-ion battery (AGDIB), which utilizes aluminum as a low-cost anode and natural graphite as the cathode. During charging, chloroaluminate anions intercalate into the graphite matrix, while metallic aluminum is deposited from the electrolyte. Key electrolytes under investigation include ionic liquids like [EMIm]Cl and AlCl3 or triethylamine hydrochloride (TEA) and AlCl3,3, 4 as well as deep-eutectic solvents, such as a urea and AlCl3 mixture, which are less toxic than traditional electrolytes.5 The AGDIB also offers high power densities, reaching up to 9 kW kgGraphite⁻¹ in laboratory-scale cells.
We first examined the electrical conductivity of various ionic liquids and deep-eutectic solvents using electrochemical impedance spectroscopy (EIS). As anticipated, [EMIm]Cl-based ionic liquids exhibited the highest conductivity (14 mS cm⁻¹) compared to deep-eutectic solvents (1.0 mS cm⁻¹), which is crucial for high-power applications.
Next, we investigated the kinetics of aluminum plating/stripping from ionic liquids on aluminum substrates. Our analysis demonstrated that using specific alloys with defined compositions, such as high magnesium (Al-5128) and manganese (Al-3104) content, enhanced the kinetics compared to typical Al foil. These findings were validated in a laboratory-scaled AIB battery, which showed superior cycling behavior at high currents.
We also focused on developing large-scale pouch cells. Single-layer pouch cells were designed with a corrosion-stable configuration using a patented bag-in-bag design, achieving excellent cycling behavior up to 10C without degradation. By increasing mass loading and double-side coating of the molybdenum current collector, we created two-layer pouch cells with 100 mAh capacity, capable of cycling up to 10C but experiencing slight capacity fading due to polarization effects. Four-layer cells were established with optimized procedures, achieving 210 mAh capacity and cycling up to 6C without observable degradation.
For the first time, the AGDIB was tested for grid stabilization, focusing on instantaneous reserve provision under dynamic pulse loads at varying temperatures (20 °C and 30 °C) and scaled to 1 and 5C. Simulation results confirmed the AGDIB’s suitability for dynamic grid stabilization and its potential contribution to stable energy supply from renewable sources. This foundational data is essential for increasing the technology readiness level (TRL) and moving toward commercial viability for rechargeable AGDIBs.