Lithium metal has the lowest standard electrochemical redox potential and very high theoretical specific capacity, making it the ultimate anode material for rechargeable batteries. However, its application in batteries has been impeded by the formation of Li whiskers, which consume the electrolyte, deplete active Li and may lead to short-circuit of the battery. Tackling these issues successfully is dependent on acquiring sufficient understanding of the formation mechanisms and growth of Li whiskers under the mechanical constraints of a separator. Here, by coupling an atomic force microscopy cantilever into a solid open-cell set-up in environmental transmission electron microscopy, we directly capture the nucleation and growth behaviour of Li whiskers under elastic constraint. We show that Li deposition is initiated by a sluggish nucleation of a single crystalline Li particle, with no preferential growth directions. Remarkably, we find that retarded surface transport of Li plays a decisive role in the subsequent deposition morphology. We then explore the validity of these findings in practical cells using a series of carbonate-poisoned ether-based electrolytes. Finally, we show that Li whiskers can yield, buckle, kink or stop growing under certain elastic constraints.

中文翻译：

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锂晶须在应力作用下形成和生长的起源。

金属锂具有最低的标准电化学氧化还原电势和非常高的理论比容量，使其成为可再充电电池的最终负极材料。然而，其在电池中的应用已受到形成锂晶须的阻碍，所述晶须消耗电解质，耗尽活性锂并可能导致电池短路。成功解决这些问题取决于在隔板的机械约束下对锂晶须的形成机理和生长有足够的了解。在这里，通过将原子力显微镜的悬臂梁耦合到环境透射电子显微镜中的固体开孔装置中，我们直接捕获了在弹性约束下锂晶须的成核和生长行为。我们表明，锂沉积是由单晶锂颗粒的缓慢成核作用引发的，没有优先的生长方向。值得注意的是，我们发现锂的表面迁移受阻在随后的沉积形态中起着决定性的作用。然后，我们使用一系列碳酸盐中毒的基于醚的电解质，探索了这些发现在实际电池中的有效性。最后，我们证明李晶须在一定的弹性约束下可以屈服，弯曲，扭结或停止生长。