Octylamine‐Supporting Interlayer Expanded Molybdenum Diselenide as a High‐Power Cathode for Rechargeable Mg Batteries

Abstract

Rechargeable Mg batteries (RMBs) are a promising large‐scale energy‐storage technology with low cost and high safety, but the performance is limited by the inferior kinetics of Mg‐intercalation cathodes. In the present study, an octylamine‐supporting interlayer expanded molybdenum diselenide (e‐MoSe2) is synthesized and used as cathode for RMBs, in comparison with ordinary crystalline MoSe2. The octylamine molecules introduced show a strong interaction with the MoSe2 layers and increase the layer spacing significantly from 6.46 to 11.5 Å. e‐MoSe2 shows a high Mg‐storage capacity of 238 mAh g−1 at 50 mA g−1 and a superior rate performance of 39 mAh g−1 at 10 A g−1, far advantageous over crystalline MoSe2. e‐MoSe2 also shows a considerably high structure stability during repeated magnesiation/demagnesiation, providing an outstanding cycling stability for 1000 cycles. Further electrochemical tests demonstrate the high Mg2+ diffusion coefficients in e‐MoSe2. Theoretical computation indicates the interlayer expansion changes the Mg2+ diffusion paths from “hollow site → hollow site” to “hollow site → Se atom site → hollow site”, largely decreasing the energy barrier and improving the Mg2+ diffusion kinetics. The present work highlights an efficient strategy for the improvement of Mg‐storage performance for RMB cathodes.