A novel, completely solid, rechargeable air battery

A novel, completely solid, rechargeable air battery
by Staff Writers
Tokyo, Japan (SPX) Jun 12, 2023

Japanese scientists have developed a unique, entirely solid, rechargeable air battery, according to a recent study published in the Angewandte Chemie International Edition on May 2, 2023. This novel battery addresses some of the key issues posed by conventional liquid electrolyte batteries and could pave the way for a new era of safer and more efficient power storage devices.

Traditionally, batteries use metals as active materials for negative electrodes. However, a growing body of recent research has demonstrated the effectiveness of redox-active organic molecules, such as quinone- and amine-based molecules, in the role of negative electrodes in rechargeable metal-air batteries with oxygen-reducing positive electrodes. These batteries have shown remarkable performance, reaching near-maximum capacity levels.

The use of redox-active organic molecules in rechargeable air batteries has been identified as a way to mitigate some of the drawbacks associated with metal-based batteries, including the formation of structures known as 'dendrites' that can harm battery performance and have a negative environmental footprint.

The study, led by Professor Kenji Miyatake from Waseda University and the University of Yamanashi, and co-authored by Professor Kenichi Oyaizu from Waseda University, has gone a step further. The team developed an all-solid-state rechargeable air battery (SSAB), replacing the problematic liquid electrolytes.

The researchers elected to use a chemical called 2,5-dihydroxy-1,4-benzoquinone (DHBQ) and its polymer poly(2,5-dihydroxy-1,4-benzoquinone-3,6-methylene) (PDBM) as active materials for the negative electrode due to their reliable and reversible redox reactions in acidic conditions. A proton-conductive polymer called Nafion was used as the solid electrolyte. "To the best of my knowledge, no air batteries based on organic electrodes and solid polymer electrolyte have been developed yet," stated Miyatake.

The newly-developed SSAB was then rigorously tested for its charge-discharge performance, rate characteristics, and cyclability. The researchers found that unlike traditional air batteries that use a metallic negative electrode and an organic liquid electrolyte, the SSAB remained undeterred by the presence of water and oxygen.

Moreover, replacing the redox-active molecule DHBQ with its polymeric counterpart PDBM resulted in an improved negative electrode. As a result, the SSAB-PDBM had a significantly higher per gram-discharge capacity than the SSAB-DHBQ, with 176.1 mAh compared to 29.7 mAh, respectively, at a constant current density of 1 mAcm-2.

The research team also reported that the coulombic efficiency of SSAB-PDBM was 84% at a 4 C rate, which gradually decreased to 66% at a 101 C rate. The discharge capacity of SSAB-PDBM reduced to 44% after 30 cycles, but the researchers managed to enhance it significantly to 78% by increasing the proton-conductive polymer content of the negative electrode. This was confirmed through electron microscopic images that showed improved performance and durability of the PDBM-based electrode with the addition of Nafion.

This groundbreaking study demonstrates a promising path towards further technological advancements in the field of energy storage. By combining redox-active organic molecules, a proton-conductive polymer, and an oxygen-reducing, diffusion type positive electrode, the researchers successfully operated an SSAB. "This technology can extend the battery life of small electronic gadgets such as smartphones and eventually contribute to realizing a carbon-free society," Miyatake concluded.

Research Report:All-Solid-State Rechargeable Air Batteries Using Dihydroxybenzoquinone and Its Polymer as the Negative Electrode