High-Performance All-Solid-State Li-S Batteries Enabled by Reaction Kinetics Enhancement and Interface Stabilization

Abstract

Compared to the conventional lithium-sulfur (Li-S) batteries using liquid electrolytes, all-solid-state lithium-sulfur batteries (ASSLSBs) own the merits of eliminating polysulfide shuttle effects, potentially higher energy density, and superior safety. However, there are challenges of low utilization of sulfur caused by poor ion and electron conductions in the cathode, huge interfacial resistance due to the contact loss caused by huge volume change of sulfur during cycling, and sluggish reaction kinetics and higher thermodynamic barriers because of the one-step reaction from S8 to Li2S reactions. Also, the carbon additive could accelerate the decomposition of sulfide solid-state electrolyte (SSE) resulting newborn impedance. Therefore, it is significant to interface engineering the carbon additive through surface modification and functionalization to improve the electrochemical stability, charge transfer, and reaction kinetics in ASSLSBs.Herein, for the first time, we designed a highly conductive carbon fiber decorated with vertically grown MoS2 nanosheets and applied it in ASSLSBs. The chemical and electrochemical compatibility among MoS2, sulfur, and sulfide SSE can greatly improve the stability of the cathode and therefore maintain pristine interfaces between the different compositions for stable ion and electron transport. The presence of electrical-conductive metallic 1T MoS2 and its uniform distribution on carbon fiber without aggregation benefit the electron transfer between carbon and sulfur. Meanwhile, the unique layered structure of MoS2 can be intercalated by a large amount of Li atoms and therefore facilitate both ionic and electronic conductivity. In consequence, the charge transfer and reaction kinetics were greatly enhanced, and the decomposition of SSEs was successfully relieved. As a result, our ASSLSB delivered an ultrahigh initial discharge capacity of 1456 mAh g-1 with ultrahigh initial coulombic efficiency and maintained high-capacity retention of 78 % at 0.1 C after 220 cycles. The batteries also obtained remarkable rate performance of 1069 mAh g-1 at 1 C. This study pioneered new idea that fabricating the high performance ASSLSBs through developing surface functionalized and stabilized conductive carbon additives with metal sulfides.