Sijia Huang, Pengfei Sang, Haojing Sun, Yongzhu Fu, Xiang Li
Lithium sulfide (Li2S) is a promising high-capacity cathode material. Importantly, it can provide lithium source, enabling lithium batteries with an anode-less/free configuration. However, Li2S suffers from poor conductivity, high polarization, low material utilization, as well as the shuttle effect, severely restricting the long cycling performance of batteries. Herein, lithium pyridine-2-thiolate (PySLi) is proposed as a multifunctional mediator for Li2S-based anode-less/free batteries. It is revealed that PySLi can modify the reaction pathway of Li2S, comprehensively enhancing its electrochemical redox kinetics and stability. Results show that the energy efficiency of the Li||Li2S cell with PySLi stabilizes at ∼80% in the full-scale range from 0.1 C to 3 C rate, which is much higher than that without PySLi (49% at 0.1 C and 22% at 3 C). The stability of the lithium metal anode is also improved, maintaining a high coulombic efficiency of >98% for 200 cycles and stable lithium stripping/plating behavior for 1000 h. Moreover, an anode-free battery based on Li2S cathode works normally for 150 cycles, and an anode-less pouch cell retains steady performance for 200 cycles. This multifunctional mediator provides a new strategy for the application of Li2S and stable anode-less/free batteries with high energy density.