Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, Los Angeles, CA, USA.
California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA, USA.
Nature. 2023 Aug;620(7972):86-91. doi: 10.1038/s41586-023-06235-w. Epub 2023 Aug 2.
Electrodeposition of lithium (Li) metal is critical for high-energy batteries. However, the simultaneous formation of a surface corrosion film termed the solid electrolyte interphase (SEI) complicates the deposition process, which underpins our poor understanding of Li metal electrodeposition. Here we decouple these two intertwined processes by outpacing SEI formation at ultrafast deposition current densities while also avoiding mass transport limitations. By using cryogenic electron microscopy, we discover the intrinsic deposition morphology of metallic Li to be that of a rhombic dodecahedron, which is surprisingly independent of electrolyte chemistry or current collector substrate. In a coin cell architecture, these rhombic dodecahedra exhibit near point-contact connectivity with the current collector, which can accelerate inactive Li formation. We propose a pulse-current protocol that overcomes this failure mode by leveraging Li rhombic dodecahedra as nucleation seeds, enabling the subsequent growth of dense Li that improves battery performance compared with a baseline. While Li deposition and SEI formation have always been tightly linked in past studies, our experimental approach enables new opportunities to fundamentally understand these processes decoupled from each other and bring about new insights to engineer better batteries.
锂（Li）金属的电沉积对于高能电池至关重要。然而，表面腐蚀膜（称为固体电解质界面，SEI）的同时形成使沉积过程变得复杂，这也加深了我们对 Li 金属电沉积的理解不足。在这里，我们通过在超快沉积电流密度下加速 SEI 形成来解耦这两个相互交织的过程，同时避免质量传输限制。通过使用低温电子显微镜，我们发现金属 Li 的固有沉积形态是菱形十二面体，这令人惊讶地独立于电解质化学或集流体基底。在硬币电池结构中，这些菱形十二面体与集流体呈近点接触连接，这可能会加速非活性 Li 的形成。我们提出了一种脉冲电流方案，通过利用 Li 菱形十二面体作为成核种子来克服这种失效模式，从而促进随后密集 Li 的生长，与基线相比可提高电池性能。虽然在过去的研究中，Li 沉积和 SEI 形成一直紧密相关，但我们的实验方法为从彼此解耦的角度来深入理解这些过程提供了新的机会，并为设计更好的电池带来了新的见解。
