Li–Se battery be a promising candidate for high energy batteries due to its theoretical gravimetric capacity of 678 mAh/g and a theoretical volumetric energy density of 3253 mAh/cm3, which is comparable with that of the Li–S battery and much higher than the LiMO2 /graphite and LiMO2 /silicon batteries. Two dimensional (2D) layered structure materials, transition metal chalcogenides (MX2; M=Mo; X: S, Se, Te) have been promising materials for Lithium rechargeable batteries due to their layered structure, remarkable electronic properties, and high theoretical specific capacity. Among these, molybdenum selenides (MoSe2) has attracted much attention. Accordingly, Se provides opportunities for developing new high-performance rechargeable batteries, including mixed chalcogenide systems, and has the potential to enhance our fundamental understanding of batteries. The layered structure of MoSe2 plus the size and electrical conductivity of Se provide a good opportunity for hosting counterions in electrochemical energy storage systems such as lithium-ion batteries. Therefore, in this report, we introduce Gr–MoSe2 were synthesized by hydrothermal method and then heating treatment. The synthesized Gr–MoSe2 was used as active cathode materials of Li-Se batteries. Mo in Gr–MoSe2 nanocomposites are electrochemically reduced (lithiation process) to give multi-layered graphene structures. Selenide compounds, Li2Se are generated inside graphene multi-layers, simultaneously in Li-Se battery. It exhibited a high reversible specific capacity of 715 mAh/g active material at 0.1 A/g and 382 mAh/g active material at 5 A/g. At a high current density of 1 A/g and a reversible discharge capacity of 560 mAh/g active material was obtained after 100 cycles. The coin cell's capacity decay rate is 0.04% per cycle for 100 cycles, with nearly 100% Coulombic efficiency throughout the cycling. Furthermore, the role of the layered graphene might provide a framework for high Li+ ion accessibility.
Figure on the left: The Gr–MoSe2 and their electrochemical reduction to give multi-layered graphene structures. During the reduction (lithiation) process down to 0.01 V vs. Li/Li + , Li–Se were generated inside graphene multi-layers, in situ. Figure on the right: Rate capability performance at various applied currents of Gr-MoSe2 (10 cycles each)
Link: https://doi.org/10.1016/j.electacta.2020.137556
The team's research results were published in the SCIE journal: Electrochimica Actac (IF=6.9) Volume 368, 1 February 2021, 137556. “High-performance Li–Se battery: Li 2 Se cathode as intercalation product of electrochemical in situ reduction of multilayer graphene-embedde d 2D-MoSe2”