Hydroxide ion-conducting viologen-bakelite organic frameworks for flexible solid-state zinc-air battery applications.
Deepak RaseRajith IllathvalappilHiman Dev SinghPragalbh ShekharLiya S LeoDebanjan ChakrabortySattwick HaldarAnkita ShelkeThalasseril G AjithkumarRamanathan VaidhyanathanPublished in: Nanoscale horizons (2023)
Adaptable polymer-based solid-state electrolytes can be a game-changer toward safe, lightweight flexible batteries. We present a robust Bakelite-type organic polymer covalently decked with viologen, triazine, and phenolic moieties. Its flexible structure with cationic viologen centers incorporates counter-balancing free hydroxide ions into the polymeric framework. By design, the aromatic groups and heteroatoms in the framework can be activated under an applied potential to prompt a push-pull drive, setting off the towing of hydroxide ions via weak electrostatic, van der Waals, and hydrogen-bond interactions. The frontier orbitals from a DFT-modeled structure certify this. The hydroxyl-polymer requires minimal KOH wetting to maintain a humid environment for Grotthuss-type transport. The hydroxide ion conductivity reaches a value of 1.4 × 10 -2 S cm -1 at 80 °C and 95% RH, which is retained for over 15 h. We enhanced its practical utility by coating it as a thin solid-state separator-cum-electrolyte on readily available filter paper. The composite exhibits a conductivity of 4.5 × 10 -3 S cm -1 at 80 °C and 95% RH. A zinc-air battery (ZAB) constructed using this polymer-coated paper as electrolyte yields a maximum power density of 115 mW cm -2 and high specific capacitance of 435 mA h g -1 . The power density recorded for our ZAB is among the best reported for polymer electrolyte-based batteries. Subsequently, the flexible battery fabricated with IISERP-POF11_OH@FilterPaper exhibits an OCV of 1.44 V, and three batteries in series power a demo traffic signal. To underscore the efficiency of hydroxide ion transport through the complex multifunctional backbone of the polymer, we calculated the diffusion coefficient for OH - (Exp: 2.9 × 10 -5 cm 2 s -1 ; Comp. 5.2 × 10 -6 cm 2 s -1 ) using electrochemical methods and MD simulations. Climbing-edge NEB calculations reveal a large energy barrier of 2.11 eV for Zn 2+ to penetrate the polymer and identify hydroxide ions within the polymer, suggesting no undesirable Zn 2+ crossover. Our findings assert the readily accessible C-C-linked cationic polymer's capacity as a solid-state electrolyte for ZABs and any anion-conducting membrane.
Keyphrases
- solid state
- aqueous solution
- reduced graphene oxide
- density functional theory
- ionic liquid
- gene expression
- quantum dots
- molecular dynamics
- gold nanoparticles
- magnetic resonance imaging
- cancer therapy
- dna methylation
- mass spectrometry
- water soluble
- high resolution
- computed tomography
- human health
- molecular docking
- open label
- study protocol
- monte carlo
- liquid chromatography
- metal organic framework