Attempts to use aluminum-based anodes in lithium-ion batteries often fail due to fast capacity fading. Generally, this has been attributed to pulverization of the electrode and the large volume changes associated with the phase transformation between the crystalline α and β phases of Li-Al alloys. In this study, these transformations were investigated in aluminum films that were lithiated either electrochemically or via direct reaction with lithium metal. Scanning electron microscopy was used to image the samples at different stages of (de)lithiation. By imaging the same locations before and after each step, it can be seen that alloying between Li and Al proceeds from distinct nucleation sites. In situ and ex situ observations reveal that the α-to-β phase transformation is highly anisotropic and causes strong distortions of the film morphology, but only a relatively small amount of mechanical damage such as cracks and delamination. Comparisons between films that were lithiated to 70% and 100% of the theoretical capacity of LiAl indicate that the critical, irreversible damage is more dependent on depth of discharge than on the volume contraction caused by delithiation. Our observations challenge the pessimistic view that pulverization is unavoidable during the phase transformations of the Li-Al system.

中文翻译：

---

锂离子电池铝阳极中相变和降解机理的见解

由于容量快速衰减，尝试在锂离子电池中使用铝基阳极的尝试通常会失败。通常，这归因于电极的粉碎以及与Li-Al合金的结晶α和β相之间的相变有关的大体积变化。在这项研究中，这些转变是在铝膜中研究的，这些铝膜经过电化学或通过与锂金属的直接反应被锂化。扫描电子显微镜用于在（去）锂化的不同阶段对样品成像。通过在每个步骤之前和之后对相同位置进行成像，可以看出Li和Al之间的合金化来自不同的成核位置。原位和异位观察表明，α-β相变具有高度的各向异性，并会引起薄膜形态的强烈变形，但只有相对少量的机械损坏，例如裂缝和分层。锂化至LiAl理论容量的70％和100％的薄膜之间的比较表明，关键的，不可逆的损害更多地取决于放电深度，而不是取决于脱锂引起的体积收缩。我们的观察结果挑战了悲观的观点，即在锂铝体系的相变过程中不可避免地要进行粉碎。