A prototype of the Organic-oxygen battery developed by the Chinese University of Hong Kong. Photo: Handout

A safe, high-rate and long-life oxygen battery that exploits a potassium biphenyl complex anode instead of the problematic potassium metal anode has recently been developed by researchers at the Chinese University of Hong Kong.

The technology promises a safe and efficient solution for the storage of renewable energy sources such as solar- and wind-generated power. The breakthrough was recently published in the world-leading scientific journal, Nature Materials, a sister journal of Nature.

Scientists have been searching for a longer-life battery that can pack in more energy more safely than the widely used lithium-ion battery. Offering a higher energy density and lower cost, alkali metal-oxygen batteries represent a promising energy storage solution for multi-scale applications including grid-scale energy storage and solar energy storage suited to powering electric vehicles. However it comes with serious limitations: poor cycle life, an unstable oxygen electrode and a flammable metal electrode.

In the past four years, Prof Yi-Chun Lu and her team have been studying the origins of the instability of oxygen batteries. Recently, they replaced the problematic potassium metal with an organic biphenyl anode forming a potassium biphenyl complex-oxygen battery, which achieves an unprecedented life of 3,000 cycles with a superior average coulombic efficiency of over 99.84%. Coulombic efficiency is defined as the ratio of the output of charge by a battery to the input of charge.

In addition, the reactions between the organic anode and bulk water or dimethyl sulfoxide proceed moderately without combustion, which makes the battery much safer compared with oxygen batteries based on alkali metals.

Developing reliable renewable energy resources is critical for sustainable development. The new organic-oxygen battery could be widely applied to large-scale electricity storage, small and medium-sized charging stations as well as energy storage modules for renewable energy harvesting systems such as solar panels and wind turbines.

The new battery has a strong potential application in distributed energy storage to enhance the penetration of renewables into the power grid. In addition, the costs of raw materials used to construct the organic-oxygen battery are much lower than the materials used in alkali metal and lithium-ion batteries, leading to a significant decrease in the cost of energy storage, according to researchers.

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