Aqueous batteries have water-based electrolyte solutions. They are safe, reliable, and inexpensive, but have relatively poor energy density and cycle life. Polymer-based batteries use organic materials from natural sources instead of bulk metals. Scientists from Harbin Institute of Technology in China, and School of Engineering at University of Tokyo, have created an all-polymer aqueous battery with flexible power.
The Rationale Behind All-Polymer Aqueous Batteries
Redox active polymers are an attractive option for battery electrodes, because these synthetic materials are readily available. They also offer high-capacity, flexibility, light weight, low cost, and low toxicity, according to Wikipedia. However, their relative inefficiency is hindering wider use of polymers in batteries.
The researchers from Japan and China understood the problems associated with the instability of polymer electrode redox products, in aqueous environments. However, they were also excited by the possibility of using flexible electrodes for advanced wearable electronic applications.
Their report that we link to below, details how the scientists developed a polymer-aqueous electrolyte. This stabilized the polymer electrode redox products, by modulating their solvation layers, and forming a solid-electrolyte interphase.
The research team chose polyanaline polymer for their all-polymer aqueous battery experiment. This was because it was suitable for both electrodes, after p-type doping. We understand that this procedure creates ‘holes’ in a semiconductor, thereby enhancing conductivity.
How the Polyanaline Organic Polymer Enabled a Breakthrough
Polyaniline is a conducting polymer and organic semiconductor of the semi-flexible rod polymer family. This compound has been of interest since the 1980’s, because of its electrical conductivity and mechanical properties. In fact, this variety is one of the most studied conducting polymers according to Wikipedia.
Including polyanaline in the design, facilitated an all-polymer aqueous battery with a high capacity of 139 milliampere-hours per gram-mass. Plus it delivered an energy density of 153 watt-hours per kilogram, with a retention of over 92% after 4800 cycles. The team hopes their discovery could herald a “paradigmatic approach to sustainable, wearable energy storage”.
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