Novel tellurium-sulfide cathode material with high-capacity and stability for Li-ion battery

Abstract

Presently commercialized metal oxide cathodes are not appropriate for large-scale batteries such as Electric Vehicles (EVs) and Energy Storage System (ESS) due to their low gravimetric and volumetric capacity (e.g. 148 mAh g-1 and 550 mAh cm-3 for LiCoO2). Also, high cost for transition metals is another barrier to facilitate large-scale batteries [1]. Recently, Sulfur (S) has received attention as a promising candidate for cathode materials because of its abundance in nature, low cost, and especially higher gravimetric and volumetric capacity (1675 mAh g-1 and 3467 mAh cm-3, respectively) than conventional transition metal oxide cathodes [1]. Despite of those attractive characteristics of S, severe capacity decay from the poor electrical conductivity (10-30 ~ 10-17 S cm-1 ) and dissolution of S and its transition into insulating low-ordered lithium polysulfides (Li2Sx, X< 4) have been hindering a long-term use for battery [2-3]. In this presentation, we introduce a new type of chalcogenide cathode material, TeS2 with highly stable cycle life. Tellurium (Te) is also one of the chalcogen materials, but metalloid with superior electrical conductivity (~2.5 S cm-1) and competitive volumetric capacity (2621 mAh cm-3 ) compared to S [3]. The composite (Li-TeS2/C) composed of TeS2 and porous carbon (Ketjen 600JD) was prepared, and its electrochemical performance as a cathode material was examined. The Li-TeS2/C showed the more stable cyclability and relatively high capacity originated from Te and S, respectively. During the synthesis,TeS2 is well impregnated into porous carbon, resulting in effective electron transfer and protection of TeS2. Dissolution of Te from cathode followed by forming solid electrolyte interface (SEI) containing Te might make the electrode more stable and increase ionic conductivity of SEI, leading to high cyclability and rate-capability.