Creating an Innovative, Solid, Air Working Battery

Posted on 30 June, 2023 by benyamin chahkandi

Summary: Typically, negative electrodes in batteries are made of active materials like metals. Rechargeable metal-air batteries with oxygen-reducing positive electrodes have recently used redox-active organic compounds, such as quinone- and amine-based molecules, as negative electrodes. Here, the redox reactions involve protons and hydroxide ions. These batteries operate well and are almost at their theoretical maximum capacity. Furthermore, using redox-active organic molecules in rechargeable air batteries eliminates issues with metals, such as the development of "dendrites," which have an adverse effect on battery performance and the environment. These batteries, like metal-based batteries, use liquid electrolytes, which raise serious safety issues due to their high electrical resistance, leaching effects, and flammability.

Now, a team of Japanese researchers has created an all-solid-state rechargeable air battery (SSAB) and examined its capacity and endurance in a new study that was published in Angewandte Chemie International Edition on May 2, 2023. Professors Kenichi Oyaizu and Kenji Miyatake, both from Waseda University and the University of Yamanashi, co-authored the paper under the direction of Professor Kenji Miyatake.

Due to their stable and reversible redox reactions in acidic environments, the researchers selected the chemical 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. They also used Nafion, a proton-conductive polymer, as the solid electrolyte in place of traditional liquid electrolytes. To the best of my knowledge, no solid polymer electrolyte and organic electrode air batteries exist.

After the SSAB was installed, the researchers experimentally evaluated its cyclability, rate characteristics, and charge-discharge performance. They discovered that the SSAB does not degrade in the presence of water and oxygen, in contrast to conventional air batteries, which use a metallic negative electrode and an organic liquid electrolyte. A superior negative electrode was created by substituting the redox-active chemical DHBQ with its polymeric analog, PDBM. At a constant current density of 1 mAcm-2, the SSAB-PDBM had a per-gram-discharge capacity of 176.1 mAh, compared to the SSAB-DHBQ's 29.7 mAh.

The researchers also discovered that the SSAB-PDBM's coulombic efficiency was 84% at 4 C rate and gradually declined to 66% at 101 C rate. After 30 cycles, the SSAB-PDBM's discharge capacity dropped to 44%, but the researchers were able to significantly increase it to 78% by adding more proton-conductive polymer to the negative electrode. The performance and durability of the PDBM-based electrode were enhanced by the addition of Nafion, according to electron microscopic images.

This study reveals the successful operation of an SSAB made up of an oxygen-reducing, diffusion-type positive electrode, a solid electrolyte made of a proton-conductive polymer, and redox-active organic molecules as the negative electrode. The researchers are hoping that it will open the door for more development. According to Miyatake, "This technology can increase the battery life of small electronic devices like smartphones and eventually help realize a carbon-free society."

source: www.sciencedaily.com/releases/2023/06/230612114704.htm