The two biggest promises of solid-state lithium (Li) metal batteries (SSLMBs) are the suppression of Li dendrites by solid-state electrolyte (SSE) and the realization of a high-energy-density Li anode. However, LMBs have not met their expectations due to Li dendrite growth causing short-circuiting. In fact, Li dendrites grow even more easily in SSE than in liquid electrolyte, but the reason for this remains unclear. Here we report in situ transmission electron microscopy observations of Li dendrite penetration through SSE and “dead” Li formation dynamics in SSLMBs. We show direct evidence that large electrochemomechanical stress generates cracks in the SSE and drives Li through the SSE directly. We revealed that fresh Li nucleation sites emerged in every discharge cycle, creating new “dead” Li in the following charging cycle and becoming the dominant Coulombic efficiency decay mechanism in SSLMBs. These results indicate that engineering flaw size and reducing electronic conductivity in SSEs are essential to improve the performance of SSLMBs.

中文翻译：

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固态锂金属电池中锂通过固体电解质和死锂动力学的原位可视化

固态锂 (Li) 金属电池 (SSLMB) 的两个最大承诺是固态电解质 (SSE) 抑制锂枝晶和实现高能量密度锂负极。然而，由于锂枝晶生长导致短路，LMBs并未达到他们的预期。事实上，锂枝晶在 SSE 中比在液体电解质中更容易生长，但其原因尚不清楚。这里我们就地报道透射电子显微镜观察锂枝晶穿透 SSE 和 SSLMB 中“死”锂的形成动力学。我们展示了直接证据表明大的电化学机械应力会在 SSE 中产生裂纹并直接驱动 Li 通过 SSE。我们发现在每个放电循环中都会出现新的锂成核位点，在接下来的充电循环中产生新的“死”锂，并成为 SSLMB 中主要的库仑效率衰减机制。这些结果表明，工程缺陷尺寸和降低 SSE 中的电子电导率对于提高 SSLMB 的性能至关重要。