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.

中文翻译：

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通过柔软的压电材料防止枝晶生长

我们报告了一种压电机制，可阻止枝晶生长，从而使锂金属电池本来就安全。为了演示，将极化的压电聚偏二氟乙烯（PVDF）膜用作隔离膜。当膜由于沉积的锂的表面不稳定性而由于任何局部突起而变形时，产生局部压电过电势以抑制锂沉积在突起上。我们的光学原位电池表明，即使从不平坦的表面开始，极化的PVDF膜也可确保沉积锂金属以形成平坦的表面。相反，在相同条件下，非偏振PVDF膜不能抑制树枝状晶体的生长，而树枝状晶体会在数分钟内穿透隔膜。纽扣电池的结果进一步证实了压电机制在实际电池应用中是有效的。⁴比无限刚性的阻滞材料的机械阻滞的最大物理极限强，这暗示了材料创新的新方向。