A salt water battery with high stability and charging rates made from solution processed conjugated polymers with polar side chains

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Moia, Davide ; Giovannitti, Alexander ; Szumska, Anna A. ; Schnurr, Martin ; Rezasoltani, Elham ; Maria, Iuliana P. ; Barnes, Piers R. F. ; McCulloch, Iain ; Nelson, Jenny (2017)
  • Subject: Physics - Applied Physics | Condensed Matter - Soft Condensed Matter

We report a neutral salt water based battery which uses p-type and n-type solution processed polymer films as the cathode and the anode of the cell. The specific capacity of the electrodes (approximately 30 mAh cm-3) is achieved via formation of bipolarons in both the p-type and n-type polymers. By engineering ethylene glycol and zwitterion based side chains attached to the polymer backbone we facilitate rapid ion transport through the non-porous polymer films. This, combined with efficient transport of electronic charge via the conjugated polymer backbones, allowed the films to maintain constant capacity at high charge and discharge rates (>1000 C-rate). The electrodes also show good stability during electrochemical cycling (less than 30% decrease in capacity over >1000 cycles) and an output voltage up to 1.4 V. The performance of these semiconducting polymers with polar side-chains demonstrates the potential of this material class for fast-charging, water based electrochemical energy storage devices.
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