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Abstract Next‐generation high‐energy‐density batteries require ideally stable metal anodes, for which smooth metal deposits during battery recharging are considered a sign of interfacial stability that can ensure high efficiency and long cycle life. With the recent successes, whether the absolute morphological stability guarantees absolute electrochemical stability and safety has emerged as a critical question to be investigated in systematic experiments under practical conditions. Here, the ideally stable ingot‐type sodium metal anode is used as a model system to identify the fast‐charging limits, that is, highest safe current density, of metal anodes. The results show that metal penetration can still occur at relatively low current densities, but the overpotentials at the penetration depend on the pore sizes of the separators and surprisingly follow a simple mathematical model developed as the Young–Laplace overpotential. This study suggests that the success of stable metal batteries with even the ideally smooth metal anode requires the holistic design of the electrolyte, separator, and metal anodes to ensure penetration‐free operation.
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A Bipolar Separator for Autonomous Suppression of Dendrite Penetration in Zinc Metal Batteries
Zinc metal anodes are attracting much attention to enable more economical and sustainable energy storage devices. However, like other metal anodes, dendritic growths and penetrations of porous separators are still challenging to eliminate. Introducing negative surface charges on the pore walls of separators have been exploited to enforce a uniform incoming Zn-ion flux toward more uniform electrodeposition, but penetrations induced by localized high current densities still remain in available systems. In this work, we report, for the first time, a bipolar separator that exploits the distinct electroosmotic effects of the negative and the positive surface charges. The surface charge effects on Zn dendrite growths were first verified in transparent capillary cells viaoperandovideo microscopy. By stacking the positively charged separator over the negatively charged separator as our proof-of-concept, the system offers preemptively a uniform Zn-ion flux through the negative layer yet starve-stops local metal growths that already penetrated the negative layer autonomously. Chronopotentiometry experiments with the symmetric cells reveal extended short-circuit time compared to control cells. Galvanostatic cycle-life experiments of full cells with the bipolar separator showed excellent cycle life of 5,000 cycles at the rate of 10 C, without signs of metal penetration.
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- Award ID(s):
- 1934122
- PAR ID:
- 10420280
- Publisher / Repository:
- The Electrochemical Society
- Date Published:
- Journal Name:
- Journal of The Electrochemical Society
- Volume:
- 170
- Issue:
- 6
- ISSN:
- 0013-4651
- Page Range / eLocation ID:
- Article No. 060511
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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