Nature of extra capacity in MoS2 electrodes: Molybdenum atoms accommodate with lithium

Two-dimensional (2D) layered transition metal sulfide based materials are promising candidates for electrodes of lithium ion batteries (LIBs). As one of the representatives, molybdenum disulfide (MoS 2 ), exhibits additional reversible capacity beyond their theoretical value although the lithium storage mechanism is still poorly understood. In this report, we developed a highly conducting metallic phase 1T(octahedral)-MoS 2 based electrode with metal Mo atoms confined in “graphene nanoreactor” of abnormal lithium-storage sites, which delivered a high specific capacity of ~1800 mAh g −1 at 1 A g -1 , about 2.6 times of its intercalation reactions value. Contrary to previous reports, a new lithium-storage mechanism for the high and ever-increasing capacity was proposed. The theoretical calculations and experiments show that a major contribution to the extra capacity in MoS 2 anodes is due to Mo atoms accommodate with Li + . The Mo precipitates and their full contact with Li 2 S matrix enabled the reversible Mo→Li x Mo→Mo→1T-MoS 2 reaction during charging/discharging processes. Over prolonged cycling, per Mo atomic could accommodate six Li + ions. This new proposal could help to establish an accurate electrochemical reaction mechanism of MoS 2 LIBs, which may lead to inspiration on new methods to greatly improve the performance of the MoS 2 anode.