Interfacial structural and chemical evolution underpins safety, energy density, and lifetime in batteries and other electrochemical systems. During lithium electrodeposition, local nonequilibrium conditions can arise that promote heterogeneous lithium morphologies but are challenging to directly study, particularly at the nanoscale. Here we map chemical microenvironments at the active copper/electrolyte interface during lithium electrodeposition, presenting operando freezing cryogenic electron microscopy (cryo-EM), a new method, to lock in structures arising in coin cells. We find local ion depletion is correlated with lithium whiskers but not planar lithium, and we hypothesize that depletion stems from root-growing whiskers consuming ions at the growth interface while also restricting ion transport through local electrolyte. This can allow dangerous lithium morphologies to propagate, even in concentrated electrolytes, as ion depletion favors dendritic growth. Operando freezing cryo-EM thus reveals local microenvironments at active electrochemical interfaces to enable direct investigation of site-specific, nonequilibrium conditions that arise during operation of energy devices.

中文翻译：

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使用操作冷冻冷冻电子显微镜绘制活性电化学界面处的离子损耗微环境

界面结构和化学演化支撑着电池和其他电化学系统的安全性、能量密度和寿命。在锂电沉积过程中，可能会出现局部非平衡条件，从而促进异质锂形态，但直接研究具有挑战性，特别是在纳米尺度上。在这里，我们绘制了锂电沉积过程中活性铜/电解质界面的化学微环境，提出了操作冷冻低温电子显微镜（cryo-EM），这是一种锁定纽扣电池中出现的结构的新方法。我们发现局部离子损耗与锂晶须相关，但与平面锂无关，并且我们假设损耗源于根部生长的晶须在生长界面消耗离子，同时也限制了离子通过局部电解质的传输。即使在浓电解质中，这也会导致危险的锂形态传播，因为离子耗尽有利于枝晶的生长。因此，操作冷冻冷冻电镜揭示了活性电化学界面的局部微环境，从而能够直接研究能源设备运行过程中出现的特定位置的非平衡条件。