He Yufang, Zhang Mengyun, Wang Aiping, Zhang Bo, Pham Hiep, Hu Qiao, Sheng Li, Xu Hong, Wang Li, Park Jonghyun, He Xiangming
Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China.
Department of Mechanical Engineering and Aerospace Engineering, Missouri University of Science and Technology, Rolla, Missouri 65401, United States.
ACS Appl Mater Interfaces. 2022 Jul 13. doi: 10.1021/acsami.2c05801.
Lithium (Li) deposition behavior plays an important role in dendrite formation and the subsequent performance of lithium metal batteries. This work reveals the impact of the lithiophilic sites of lithium-alloy on the Li plating process via the first-principles calculations. We find that the Li deposition mechanisms on the Li metal and LiSn surface are different due to the lithiophilic sites. We first propose that Li plating on the Li metal surface goes through the "adsorption-reduction-desorption-heterogeneous nucleation-cluster drop" process, while it undergoes the "adsorption-reduction-growth" process on the LiSn surface. The lower adsorption energy contributes to the easy adsorption of Li on the lithiophilic sites of the LiSn surface. The lower Li reduction energy on the Li metal surface indicates that it is easy for Li to be reduced on the Li metal surface, attributed to its higher Fermi energy level. Furthermore, the faster Li diffusion on the LiSn surface results in smooth Li deposition, which is based on a "two-Li synergy diffusion" mechanism. However, Li diffuses more slowly on the Li metal surface than on the LiSn surface due to the "single Li diffusion" mechanism. This work provides a fundamental understanding on the impact of lithiophilic sites of Li alloy on the Li plating process and points out that the future design of 3D Li-alloy substrates decorated with multilithiophilic sites can prevent dendrite formation on the lithium-alloy substrate by guiding uniform Li deposition.
锂（Li）沉积行为在枝晶形成及随后的锂金属电池性能中起着重要作用。这项工作通过第一性原理计算揭示了锂合金的亲锂位点对锂电镀过程的影响。我们发现，由于亲锂位点的存在，锂在锂金属和LiSn表面的沉积机制不同。我们首次提出，锂在锂金属表面的电镀经历“吸附-还原-解吸-异质成核-团簇掉落”过程，而在LiSn表面则经历“吸附-还原-生长”过程。较低的吸附能有助于锂在LiSn表面的亲锂位点上轻松吸附。锂在锂金属表面较低的还原能表明，由于其较高的费米能级，锂在锂金属表面易于被还原。此外，基于“双锂协同扩散”机制，锂在LiSn表面更快的扩散导致锂的沉积平滑。然而，由于“单锂扩散”机制，锂在锂金属表面的扩散比在LiSn表面更慢。这项工作为理解锂合金的亲锂位点对锂电镀过程的影响提供了基础，并指出未来设计具有多个亲锂位点的三维锂合金基底可以通过引导锂的均匀沉积来防止锂合金基底上枝晶的形成。
