Cryo‐Electron Tomography of Highly Deformable and Adherent Solid‐Electrolyte Interphase Exoskeleton in Li‐Metal Batteries with Ether‐Based Electrolyte
Cryo‐Electron Tomography of Highly Deformable and Adherent Solid‐Electrolyte Interphase Exoskeleton in Li‐Metal Batteries with Ether‐Based Electrolyte
复制标题
具有醚基电解质的锂金属电池中高度可变形和粘附的固体电解质界面外骨架的冷冻电子断层扫描
DOI：
10.1002/adma.202108252
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发表时间：
2022
影响因子：
29.4
通讯作者：
Li, Ju
中科院分区：
文献类型：
--
作者：
Han, Bing;Li, Xiangyan;Wang, Qi;Zou, Yucheng;Xu, Guiyin;Cheng, Yifeng;Zhang, Zhen;Zhao, Yusheng;Deng, Yonghong;Li, Ju
利用低温透射电镜分析了镀锂（LiMetal）和固体电解质界面（SEI）的三维纳米复合结构，包括富含聚合物的表面钝化层（SEI外骨骼）和埋在非晶锂基体中的无机SEI“化石”。使用醚基DOLDME - LiTFSI电解质，LiF和Li2O纳米晶体形成并嵌入SEI外骨骼中的薄而坚韧的非晶聚合物中。锂离子的快速剥离方向是沿直线的，在半充电时产生8个暴露平面。完全的锂剥离会产生完全下垂的空SEI外壳，可以承受大的弯曲和屈曲，最小的弯曲半径接近几十纳米而没有明显的损伤。在第二轮镀锂过程中，薄的libcc片首先在集电流处成核，延伸到放气的SEI外壳的顶端，然后扩大其厚度。libcc与SEI内部的明显零润湿角意味着非均相成核能势垒为零。由于其完全润湿特性和化学机械稳定性，SEI在很大程度上阻止了锂金属和电解质之间的进一步反应，这解释了锂金属电池与乙醚基电解质的优越性能。然而，在第二次电镀过程中，SEI外壳的不均匀填充导致了枝晶突出和一些新的SEI形成。在初始循环中形成更大的SEI胶囊，其能量密度高于后续循环，从而进一步将库仑效率提高到99%以上。
The 3D nanocomposite structure of plated lithium (LiMetal) and solid electrolyte interphases (SEI), including a polymer‐rich surficial passivation layer (SEI exoskeleton) and inorganic SEI “fossils” buried inside amorphous Li matrix, is resolved using cryogenic transmission electron microscopy. With ether‐based DOLDME‐LiTFSI electrolyte, LiF and Li2O nanocrystals are formed and embedded in a thin but tough amorphous polymer in the SEI exoskeleton. The fast Li‐stripping directions are alongor, which produces eight exposed {111} planes at halfway charging. Full Li stripping produces completely sagging, empty SEI husks that can sustain large bending and buckling, with the smallest bending radius of curvature observed approaching tens of nanometers without apparent damage. In the 2nd round of Li plating, a thin LiBCCsheet first nucleates at the current collector, extends to the top end of the deflated SEI husk, and then expands its thickness. The apparent zero wetting angle between LiBCCand the SEI interior means that the heterogeneous nucleation energy barrier is zero. Due to its complete‐wetting property and chemo‐mechanical stability, the SEI largely prevents further reactions between the Li metal and the electrolyte, which explains the superior performance of Li‐metal batteries with ether‐based electrolytes. However, uneven refilling of the SEI husks results in dendrite protrusions and some new SEI formation during the 2nd plating. A strategy to form bigger SEI capsules during the initial cycle with higher energy density than the following cycles enables further enhanced Coulombic efficiency to above 99%.