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Preventing Dendrite Growth by a Soft Piezoelectric Material

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posted on 02.10.2019, 16:38 by Guangyu Liu, Dandan Wang, Jianyu Zhang, Andrew Kim, Wei Lu
We report a piezoelectric mechanism to stop dendrite growth, which enables inherently safe lithium metal battery. For demonstration, a polarized piezoelectric polyvinylidene fluoride (PVDF) film is used as a separator. When the film is deformed by any local protrusion because of surface instability of the deposited lithium, a local piezoelectric over-potential is generated to suppress lithium deposition on the protrusion. Our optical in situ cell shows that a polarized PVDF film ensures lithium metal depositing to form a flat surface, even when starting from an uneven surface. In contrast, a nonpolarized PVDF film cannot suppress dendrite growth under the same condition, with dendrite penetrating the separator within minutes. Coin cell results further confirm that the piezoelectric mechanism is effective in practical battery applications. Analysis suggests that the effectiveness of piezoelectric mechanism by over-potential is easily 104 stronger than the maximum physical limit of mechanical blocking from infinitely stiff blocking materials, suggesting a new direction of material innovation.