College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China.
State Key Lab of Chemical Resource Engineering, College of Science & College of Energy, Beijing University of Chemical Technology, Beijing, 100092, China.
Adv Mater. 2019 Oct;31(41):e1903248. doi: 10.1002/adma.201903248. Epub 2019 Aug 29.
Uncontrollable Li dendrite growth and low Coulombic efficiency severely hinder the application of lithium metal batteries. Although a lot of approaches have been developed to control Li deposition, most of them are based on inhibiting lithium deposition on protrusions, which can suppress Li dendrite growth at low current density, but is inefficient for practical battery applications, with high current density and large area capacity. Here, a novel leveling mechanism based on accelerating Li growth in concave fashion is proposed, which enables uniform and dendrite-free Li plating by simply adding thiourea into the electrolyte. The small thiourea molecules can be absorbed on the Li metal surface and promote Li growth with a superfilling effect. With 0.02 m thiourea added in the electrolyte, Li | Li symmetrical cells can be cycled over 1000 cycles at 5.0 mA cm , and a full cell with LiFePO | Li configuration can even maintain 90% capacity after 650 cycles at 5.0 C. The superfilling effect is also verified by computational chemistry and numerical simulation, and can be expanded to a series of small chemicals using as electrolyte additives. It offers a new avenue to dendrite-free lithium deposition and may also be expanded to other battery chemistries.
不可控的锂枝晶生长和低库仑效率严重阻碍了锂电池的应用。尽管已经开发了许多方法来控制锂的沉积，但大多数方法都是基于抑制凸起处的锂沉积，这可以在低电流密度下抑制锂枝晶的生长，但对于实际电池应用效率不高，需要高电流密度和大面积容量。在这里，提出了一种基于加速凹形锂生长的新型平整机制，通过简单地在电解液中添加硫脲，可以实现均匀的无枝晶锂电镀。小的硫脲分子可以被吸附在锂金属表面上，并通过超填充效应促进锂的生长。在电解液中添加 0.02 m 的硫脲，Li | Li 对称电池可以在 5.0 mA cm 的电流密度下循环 1000 次以上，而具有 LiFePO | Li 构型的全电池甚至可以在 5.0 C 的电流密度下保持 650 次循环后 90%的容量。超填充效应也通过计算化学和数值模拟得到了验证，并可以扩展到一系列用作电解液添加剂的小化学物质。它为无枝晶锂沉积提供了新途径，也可能扩展到其他电池化学领域。
