A team of researchers from the University of Adelaide in Australia and the University of Maryland in the U.S. have developed a new type of aqueous sodium-ion battery that they claim can last for over 13,000 charge cycles, overcoming a key limitation of aqueous batteries: water decomposition.

The findings, published in the journal Nature Communications, show that the researchers created an alkaline, rather than neutral, electrolyte that suppresses water splitting into oxygen and hydrogen.

Traditional aqueous batteries, like lead-acid batteries, contain water-based electrolytes. While safe and low-cost, a downside is that the water can decompose during battery cycling, producing hydrogen gas that limits battery lifespan and poses safety risks.

However, alkaline conditions can trigger corrosion of the battery cathode. To prevent this, the researchers coated the cathode with nickel/carbon nanoparticles, which created a locally acidic environment at the cathode surface to mitigate corrosion.

The nickel coating had another benefit – some nickel atoms embedded into the cathode, reinforcing its structure against degradation. This combination of the tailored alkaline electrolyte and nickel-carbon coating led to the coin cell battery maintaining 85% of its initial capacity after 1,000 charge/discharge cycles.

The alkaline solution is also cheaper than current methods to boost water stability, which contains expensive fluorine salts and the addition of potentially flammable co-solvents to the electrolyte to reduce water activity.

According to the researchers, the aqueous sodium-ion battery demonstrated an energy density of 90 Wh/kg, which is good for an aqueous battery but still lower than the 120-260 Wh/kg seen in lithium-ion batteries. However, unlike lithium, sodium has a high natural abundance on the planet, which helps lower costs.

The researchers believe it could enable large-scale energy storage to support renewables and electric vehicles if it can be successfully commercialized. It could also be useful for underwater electronics due to its safety and long lifetime.

There is research in other sodium-ion battery chemistries emerging to address the challenges in performance and cost. Pune-headquartered KPIT Technologies in December unveiled a sodium-ion battery technology with 80% capacity retention for 3,000-6,000 cycles and energy density ranging from 100-170 Wh/Kg.

In May, scientists at the Indian Institute of Technology Bombay claimed a breakthrough in developing sodium-ion batteries by addressing the challenges of air/water instability and structural-cum-electrochemical instability in cathode materials.