ABSTRACT
Lithium-sulfur (Li-S) batteries using Li2S and Li-free anodes have emerged as a potential high-energy and safe battery technology. Although the operation of Li-S full batteries based on Li2S has been demonstrated at room temperature, their effective use at a subzero temperature has not been realized due to the low electrochemical utilization of Li2S. Here, ammonium nitrate (NH4NO3) is introduced as a functional additive that allows Li-S full batteries to operate at -10 °C. The polar N-H bonds in the additive alter the activation pathway of Li2S by inducing the dissolution of the Li2S surface. Then, Li2S with an amorphized surface layer undergoes the modified activation process, which consists of the disproportionation and direct conversion reaction, through which Li2S is efficiently converted into S8. The Li-S full battery using NH4NO3 delivers a reversible capacity and cycling stability over 400 cycles at -10 °C.
ABSTRACT
To realize lithium-sulfur (Li-S) batteries with high energy density, it is crucial to maximize the loading level of sulfur cathode and minimize the electrolyte content. However, excessive amounts of lithium polysulfides (LiPSs) generated during the cycling limit the stable operation of Li-S batteries. In this study, a high-loading S cathode with a three-dimensional (3D) network structure is fabricated using a simple pelletizing method, and the exhausting overcharging phenomenon, which occurs in the high-loading Li-S cell, is successively prevented by pretreating the lithium metal anode. Moreover, adding a diluent to the electrolyte containing viscous LiPSs enables the facile conversion between S species during the cycling of high-loading Li-S cells under lean electrolyte conditions. Finally, a prototype Li-S pouch cell with high energy density (427 Wh kg-1) was realized by combining a compacted 3D cathode with a high-loading, pretreated thin lithium metal and diluent-modified electrolyte. We believe that the results reported herein will be a good guideline to establish proper strategies to achieve high energy density Li-S batteries.
