A conductive carbon rubber sheet used as the cathode current collector has given an aqueous aluminum-ion battery from Green Science Alliance an initial capacity of at least 210 mAh/g, held for at least 25 cycles. The Japanese company says that the cheap sheet can replace costly corrosion-resistant metals.
Snapshot
Company: Green Science Alliance
Battery: Aqueous Al-ion
Initial capacity: 210 mAh/g
Earlier capacity: 103 mAh/g
Cycles held: 25 cycles
Cell voltage: 0.9-1.0 V
Projected cost: Below $55/kWh
Green Science Alliance, a Japan-based battery developer, has reported a stable rechargeable aqueous aluminum-ion battery (AAIB) that uses a cheap conductive carbon rubber sheet as its cathode current collector. At 0.025 C and room temperature, the cell showed an initial capacity of at least 210 mAh/g, which held for at least 25 cycles. The company says that the measurement is still going on.
The result improves on the company's earlier AAIB, which started at about 103 mAh/g and had poor cycle stability. In cyclic voltammetry run below 1.23 V, the voltage at which water splits, the redox peaks of charge and discharge were still present after 100 cycles. Each cell gives 0.9-1.0 V, lower than a lithium-ion cell, which the company says can be solved by connecting cells in series.
The company's researcher puts the gain down to the porous sheet. The cathode material fills its pores to form a 3D composite, while the carbon in the sheet keeps conductive paths open and also acts as cathode material. The aqueous electrolyte soaks into the structure and widens the surface for the reaction. A dense carbon plate used as the collector did not give the same performance.
The cell uses graphite as the cathode, ordinary paper as the separator, a concentrated aqueous aluminum perchlorate solution as the electrolyte and an aluminum anode of a special composition. Aqueous cells can be built in normal air without inert gas. They also avoid the expensive corrosion-resistant metals, such as molybdenum, niobium and tantalum, that ionic-liquid aluminum-ion designs need for the current collector. The release puts lithium-ion costs at about $115 per kWh and projected aluminum-ion costs at $55-60 per kWh at scale, and says that the aqueous version could come in below $55 per kWh.
Part of the results will be presented at the 250th Meeting of The Electrochemical Society (ECS) in Calgary, Canada, in October 2026. The company plans further work on capacity and cycle stability, with industrial use as the goal.
Green Science Alliance is based in Kawanishi, Japan. Its researcher, the inventor of the aqueous aluminum battery, published a review of the work in the Royal Society of Chemistry journal Energy Advances in 2025.