Understanding LiI-LiBr Catalyst Activity for Solid State Li<sub>2</sub>S/S Reactions in an All-Solid-State Lithium Battery
Hongli Wan, Bao Zhang, Sufu Liu, Jiaxun Zhang, Xiayin Yao, Chunsheng Wang
Abstract
Li||MoS2 solid-state batteries have higher volumetric energy density and power density than Li||Li2S batteries. However, they suffer from energy and power decay due to the formation of lithium sulfide that has low ionic/electronic conductivity and a strong Li–S bond. Herein, we overcome these challenges by incorporating the catalytic LiI-LiBr compound and carbon black into MoS2. The comprehensive simulations, characterizations, and electrochemical evaluations demonstrated that LiI-LiBr significantly reduces Li+/S2– interaction and increases the ionic conductivity of Li2S, thus enhancing the reaction kinetics and Li2S/S redox reversibility. MoS2@LiI-LiBr@C||Li cells with an areal capacity of 0.87 mAh cm–2 provide a reversible capacity of 816.2 mAh g–1 at 200 mA g–1 and maintain 604.8 mAh g–1 (based on the mass of MoS2) for 100 cycles. At a high areal capacity of 2 mAh cm–2, the battery still delivers reversible capacity of 498 mAh g–1. LiI-LiBr-carbon additive can be broadly applied for all transition-metal sulfide cathodes to enhance the cyclic and rate performance.