Two-Phase Electrochemical Proton Transport and Storage in α-MoO3 for Proton Batteries

• Published in: Cell reports physical science Vol. 1; no. 10; p. 100225
• Main Authors: Guo, Haocheng, Goonetilleke, Damian, Sharma, Neeraj, Ren, Wenhao, Su, Zhen, Rawal, Aditya, Zhao, Chuan
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 21-10-2020; Elsevier
• Subjects: batteries; EQCM; hydrogen bronzes; hydronium; ion-electrode interaction; MoO3; operando; proton; transport; hydronium; MoO3; batteries; hydrogen bronzes; EQCM; transport; operando; ion-electrode interaction; proton
• ISSN: 2666-3864; 2666-3864
• DOI: 10.1016/j.xcrp.2020.100225

Diffusion-controlled charge storage and phase transitions of electrodes are typical indicators of sluggish kinetics in battery chemistries. However, fast rate capabilities are found in an α-MoO3 proton intercalation electrode that presents both features. Here, the unique topochemistry is shown to involve multiple ion-electrode interactions and proceeds via two key steps: hydronium adsorption on surfaces and proton insertion into bulk lattices. This triggers structure transitions from MoO3 to hydrogen molybdenum bronzes (HMBs). Following the first process, subsequent rearrangements proceed only among HMBs phases with high reversibility and kinetics, thus providing structural explanations to the fast rate capability. At electrode-electrolyte interfaces, hydronium is the active charge carrier that initiates charge transfer and surface hydration, which are accompanied by water adsorption/desorption with reduced polarization and enhanced kinetics. Further water activity is shown to induce material dissolution during function. These findings offer fundamental insights in proton chemistries, which may form the basis of future high rate and capacity energy storage.
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Operando XRD and EQCM reveal two scenarios of proton transport and intercalationHydroniums transport charge at interfaces with inverse water movementNaked protons insert into electrode lattices to trigger bulk structure transitionWater activities induce surface hydration and influence cycling stability
Hydrogen ions (proton/hydronium) are promising charge carriers for future high rate and capacity energy storage. Here, Guo et al. investigate the protonation topochemistry of α-MoO3 involving sophisticated hydronium/water interplay with electrode surfaces and proton insertion-triggered bulk reactions, which enable a diffusion-dominated electrode also to present rapid rates.