Lithium-metal batteries have a very high theoretical specific capacity. However, they come with some challenges, such as side reactions between a lithium metal anode and the electrolyte and the formation of lithium dendrites. The latter can lead to short circuits and fires. There are several approaches to curbing dendrite growth. The use of electrolyte additives could be a particularly simple and cost-effective one. Carbon dots (CDs), a type of carbon nanomaterial, for example, can be homogeneously dispersed in the electrolyte solution and modified with lithiophilic components. The resulting CDs could regulate the transport and deposition of Li ions.
Hongshuai Hou, Central South University, Changsha, China, and colleagues have developed bismuth-doped carbon dots (Bi-CDs) to be used as co-deposition electrolyte additives in lithium–sulfur batteries. The team synthesized the Bi-CDs using a one-step hydrothermal method with glucose and bismuth potassium citrate as precursors. The resulting Bi-CDs have abundant oxygen-containing groups and can be uniformly dispersed in the electrolyte.
The doped carbon dots can bind lithium ions, leading to a reduced aggregation and an even dispersion of the lithium ions in the electrolyte. They also serve as nucleation sites, which ensures uniform lithium deposition on the electrode and prevents the formation of dendrites. When the Bi-CDs were used in a conventional electrolyte for high-performance Li–S batteries, the researchers observed a high coulombic efficiency of 99.0 % and long-term stability for 800 h.
- Bi-doped carbon dots for a stable lithium metal anode,
Hanyu Tu, Shuo Li, Zheng Luo, Laiqiang Xu, Hao Zhang, Yinger Xiang, Wentao Deng, Guoqiang Zou, Hongshuai Hou, Xiaobo Ji,
Chem. Commun. 2022.